Support for sparse/dense vectors in the python extension

- SparseVector, DenseVector
- improved Lattice
- Lattice translation
- Hypergraph reweighting, pruning

10 files changed, 5378 insertions, 1843 deletions

diff --git a/python/src/_cdec.cpp b/python/src/_cdec.cpp
index 55470c89..0b9b9911 100644
--- a/python/src/_cdec.cpp
+++ b/python/src/_cdec.cpp
@@ -1,4 +1,4 @@
-/* Generated by Cython 0.16 on Thu Jun 14 09:24:35 2012 */
+/* Generated by Cython 0.16 on Sat Jun 23 11:57:21 2012 */
 
 #define PY_SSIZE_T_CLEAN
 #include "Python.h"
@@ -272,11 +272,12 @@
 #define __PYX_HAVE_API___cdec
 #include <string>
 #include <vector>
+#include <utility>
 #include <iostream>
 #include "utils/weights.h"
 #include "utils/logval.h"
-#include "utils/prob.h"
 #include "utils/wordid.h"
+#include "utils/small_vector.h"
 #include "utils/sparse_vector.h"
 #include "utils/tdict.cc"
 #include "utils/verbose.h"
@@ -289,6 +290,7 @@
 #include "decoder/hg_io.h"
 #include "decoder/hg_intersect.h"
 #include "decoder/hg_sampler.h"
+#include "decoder/csplit.h"
 #include "decoder/ff_register.h"
 #include "decoder/decoder.h"
 #include "observer.h"
@@ -376,46 +378,32 @@ static const char *__pyx_filename;
 
 static const char *__pyx_f[] = {
   "_cdec.pyx",
+  "vectors.pxi",
+  "hypergraph.pxi",
+  "lattice.pxi",
 };
 
 /*--- Type declarations ---*/
-struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree;
-struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample;
-struct __pyx_obj_5_cdec_Weights;
+struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample;
+struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__;
+struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree;
 struct __pyx_obj_5_cdec_Decoder;
+struct __pyx_obj_5_cdec_SparseVector;
 struct __pyx_obj_5_cdec_Hypergraph;
 struct __pyx_obj_5_cdec_Lattice;
+struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__;
 struct __pyx_obj_5_cdec___pyx_scope_struct____iter__;
-struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest;
+struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest;
+struct __pyx_obj_5_cdec_DenseVector;
 
-/* "_cdec.pyx":105
+/* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":56
  *         del derivations
  * 
- *     def kbest_tree(self, size):             # <<<<<<<<<<<<<<
- *         assert (self.hg != NULL)
- *         cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ETreeTraversal](self.hg[0], size)
- */
-struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree {
-  PyObject_HEAD
-  KBest::KBestDerivations<std::vector<WordID>,ETreeTraversal>::Derivation *__pyx_v_derivation;
-  KBest::KBestDerivations<std::vector<WordID>,ETreeTraversal> *__pyx_v_derivations;
-  unsigned int __pyx_v_k;
-  struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self;
-  PyObject *__pyx_v_sentence;
-  PyObject *__pyx_v_size;
-  unsigned int __pyx_t_0;
-  long __pyx_t_1;
-};
-
-
-/* "_cdec.pyx":122
- *         hypergraph.Intersect(lat.lattice[0], self.hg)
- * 
  *     def sample(self, unsigned n):             # <<<<<<<<<<<<<<
- *         assert (self.hg != NULL)
  *         cdef vector[hypergraph.Hypothesis]* hypos = new vector[hypergraph.Hypothesis]()
+ *         if self.rng == NULL:
  */
-struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample {
+struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample {
   PyObject_HEAD
   std::vector<HypergraphSampler::Hypothesis> *__pyx_v_hypos;
   unsigned int __pyx_v_k;
@@ -427,35 +415,73 @@ struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample {
 };
 
 
-/* "_cdec.pyx":15
- *     pass
+/* "/Users/vchahun/Sandbox/cdec/python/src/vectors.pxi":43
+ *         self.vector.set_value(fid, value)
  * 
- * cdef class Weights:             # <<<<<<<<<<<<<<
- *     cdef vector[weight_t]* weights
+ *     def __iter__(self):             # <<<<<<<<<<<<<<
+ *         cdef FastSparseVector[weight_t].const_iterator* it = new FastSparseVector[weight_t].const_iterator(self.vector[0], False)
+ *         cdef str fname
+ */
+struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ {
+  PyObject_HEAD
+  PyObject *__pyx_v_fname;
+  size_t __pyx_v_i;
+  FastSparseVector<weight_t>::const_iterator *__pyx_v_it;
+  struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self;
+  size_t __pyx_t_0;
+  size_t __pyx_t_1;
+};
+
+
+/* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":44
+ *         del derivations
  * 
+ *     def kbest_tree(self, size):             # <<<<<<<<<<<<<<
+ *         cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ETreeTraversal](self.hg[0], size)
+ *         cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal].Derivation* derivation
  */
-struct __pyx_obj_5_cdec_Weights {
+struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree {
   PyObject_HEAD
-  std::vector<weight_t> *weights;
+  KBest::KBestDerivations<std::vector<WordID>,ETreeTraversal>::Derivation *__pyx_v_derivation;
+  KBest::KBestDerivations<std::vector<WordID>,ETreeTraversal> *__pyx_v_derivations;
+  unsigned int __pyx_v_k;
+  struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self;
+  PyObject *__pyx_v_size;
+  PyObject *__pyx_v_tree;
+  unsigned int __pyx_t_0;
+  long __pyx_t_1;
 };
 
 
-/* "_cdec.pyx":38
- *             yield FDConvert(fid).c_str(), self.weights[0][fid]
+/* "_cdec.pyx":15
+ *     pass
  * 
  * cdef class Decoder:             # <<<<<<<<<<<<<<
  *     cdef decoder.Decoder* dec
- *     cdef public Weights weights
+ *     cdef public DenseVector weights
  */
 struct __pyx_obj_5_cdec_Decoder {
   PyObject_HEAD
   Decoder *dec;
-  struct __pyx_obj_5_cdec_Weights *weights;
+  struct __pyx_obj_5_cdec_DenseVector *weights;
 };
 
 
-/* "_cdec.pyx":71
- *         return hg
+/* "/Users/vchahun/Sandbox/cdec/python/src/vectors.pxi":32
+ *         return sparse
+ * 
+ * cdef class SparseVector:             # <<<<<<<<<<<<<<
+ *     cdef FastSparseVector[weight_t]* vector
+ * 
+ */
+struct __pyx_obj_5_cdec_SparseVector {
+  PyObject_HEAD
+  FastSparseVector<weight_t> *vector;
+};
+
+
+/* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":4
+ * cimport kbest as kb
  * 
  * cdef class Hypergraph:             # <<<<<<<<<<<<<<
  *     cdef hypergraph.Hypergraph* hg
@@ -468,8 +494,8 @@ struct __pyx_obj_5_cdec_Hypergraph {
 };
 
 
-/* "_cdec.pyx":139
- *     # TODO: inside-outside pruning
+/* "/Users/vchahun/Sandbox/cdec/python/src/lattice.pxi":3
+ * cimport lattice
  * 
  * cdef class Lattice:             # <<<<<<<<<<<<<<
  *     cdef lattice.Lattice* lattice
@@ -481,41 +507,70 @@ struct __pyx_obj_5_cdec_Lattice {
 };
 
 
-/* "_cdec.pyx":33
- *         self.weights[0][fid] = value
+/* "/Users/vchahun/Sandbox/cdec/python/src/lattice.pxi":50
+ *         return hypergraph.AsPLF(self.lattice[0], True).c_str()
+ * 
+ *     def __iter__(self):             # <<<<<<<<<<<<<<
+ *         cdef unsigned i
+ *         for i in range(len(self)):
+ */
+struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ {
+  PyObject_HEAD
+  unsigned int __pyx_v_i;
+  struct __pyx_obj_5_cdec_Lattice *__pyx_v_self;
+  Py_ssize_t __pyx_t_0;
+  unsigned int __pyx_t_1;
+};
+
+
+/* "/Users/vchahun/Sandbox/cdec/python/src/vectors.pxi":18
+ *         self.vector[0][fid] = value
  * 
  *     def __iter__(self):             # <<<<<<<<<<<<<<
  *         cdef unsigned fid
- *         for fid in range(1, self.weights.size()):
+ *         for fid in range(1, self.vector.size()):
  */
 struct __pyx_obj_5_cdec___pyx_scope_struct____iter__ {
   PyObject_HEAD
   unsigned int __pyx_v_fid;
-  struct __pyx_obj_5_cdec_Weights *__pyx_v_self;
+  struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self;
   size_t __pyx_t_0;
   unsigned int __pyx_t_1;
 };
 
 
-/* "_cdec.pyx":92
- *         return tree.decode('utf8')
+/* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":32
+ *         return fmap
  * 
  *     def kbest(self, size):             # <<<<<<<<<<<<<<
- *         assert (self.hg != NULL)
  *         cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal](self.hg[0], size)
+ *         cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal].Derivation* derivation
  */
-struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest {
+struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest {
   PyObject_HEAD
   KBest::KBestDerivations<std::vector<WordID>,ESentenceTraversal>::Derivation *__pyx_v_derivation;
   KBest::KBestDerivations<std::vector<WordID>,ESentenceTraversal> *__pyx_v_derivations;
   unsigned int __pyx_v_k;
   struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self;
+  PyObject *__pyx_v_sentence;
   PyObject *__pyx_v_size;
-  PyObject *__pyx_v_tree;
   unsigned int __pyx_t_0;
   long __pyx_t_1;
 };
 
+
+/* "/Users/vchahun/Sandbox/cdec/python/src/vectors.pxi":3
+ * from cython.operator cimport preincrement as pinc
+ * 
+ * cdef class DenseVector:             # <<<<<<<<<<<<<<
+ *     cdef vector[weight_t]* vector
+ * 
+ */
+struct __pyx_obj_5_cdec_DenseVector {
+  PyObject_HEAD
+  std::vector<weight_t> *vector;
+};
+
 #ifndef CYTHON_REFNANNY
   #define CYTHON_REFNANNY 0
 #endif
@@ -572,6 +627,14 @@ struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest {
 
 static PyObject *__Pyx_GetName(PyObject *dict, PyObject *name); /*proto*/
 
+static CYTHON_INLINE void __Pyx_ErrRestore(PyObject *type, PyObject *value, PyObject *tb); /*proto*/
+static CYTHON_INLINE void __Pyx_ErrFetch(PyObject **type, PyObject **value, PyObject **tb); /*proto*/
+
+static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject *cause); /*proto*/
+
+static int __Pyx_ArgTypeTest(PyObject *obj, PyTypeObject *type, int none_allowed,
+    const char *name, int exact); /*proto*/
+
 static void __Pyx_RaiseDoubleKeywordsError(const char* func_name, PyObject* kw_name); /*proto*/
 
 static int __Pyx_ParseOptionalKeywords(PyObject *kwds, PyObject **argnames[], \
@@ -581,13 +644,12 @@ static int __Pyx_ParseOptionalKeywords(PyObject *kwds, PyObject **argnames[], \
 static void __Pyx_RaiseArgtupleInvalid(const char* func_name, int exact,
     Py_ssize_t num_min, Py_ssize_t num_max, Py_ssize_t num_found); /*proto*/
 
-static int __Pyx_ArgTypeTest(PyObject *obj, PyTypeObject *type, int none_allowed,
-    const char *name, int exact); /*proto*/
-
-static CYTHON_INLINE void __Pyx_ErrRestore(PyObject *type, PyObject *value, PyObject *tb); /*proto*/
-static CYTHON_INLINE void __Pyx_ErrFetch(PyObject **type, PyObject **value, PyObject **tb); /*proto*/
-
-static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject *cause); /*proto*/
+static CYTHON_INLINE int __Pyx_NegateNonNeg(int b) {
+    return unlikely(b < 0) ? b : !b;
+}
+static CYTHON_INLINE PyObject* __Pyx_PyBoolOrNull_FromLong(long b) {
+    return unlikely(b < 0) ? NULL : __Pyx_PyBool_FromLong(b);
+}
 
 static CYTHON_INLINE void __Pyx_RaiseNeedMoreValuesError(Py_ssize_t index);
 
@@ -595,6 +657,78 @@ static CYTHON_INLINE void __Pyx_RaiseTooManyValuesError(Py_ssize_t expected);
 
 static int __Pyx_IternextUnpackEndCheck(PyObject *retval, Py_ssize_t expected); /*proto*/
 
+static CYTHON_INLINE PyObject *__Pyx_GetItemInt_Generic(PyObject *o, PyObject* j) {
+    PyObject *r;
+    if (!j) return NULL;
+    r = PyObject_GetItem(o, j);
+    Py_DECREF(j);
+    return r;
+}
+#define __Pyx_GetItemInt_List(o, i, size, to_py_func) (((size) <= sizeof(Py_ssize_t)) ? \
+                                                    __Pyx_GetItemInt_List_Fast(o, i) : \
+                                                    __Pyx_GetItemInt_Generic(o, to_py_func(i)))
+static CYTHON_INLINE PyObject *__Pyx_GetItemInt_List_Fast(PyObject *o, Py_ssize_t i) {
+    if (likely(o != Py_None)) {
+        if (likely((0 <= i) & (i < PyList_GET_SIZE(o)))) {
+            PyObject *r = PyList_GET_ITEM(o, i);
+            Py_INCREF(r);
+            return r;
+        }
+        else if ((-PyList_GET_SIZE(o) <= i) & (i < 0)) {
+            PyObject *r = PyList_GET_ITEM(o, PyList_GET_SIZE(o) + i);
+            Py_INCREF(r);
+            return r;
+        }
+    }
+    return __Pyx_GetItemInt_Generic(o, PyInt_FromSsize_t(i));
+}
+#define __Pyx_GetItemInt_Tuple(o, i, size, to_py_func) (((size) <= sizeof(Py_ssize_t)) ? \
+                                                    __Pyx_GetItemInt_Tuple_Fast(o, i) : \
+                                                    __Pyx_GetItemInt_Generic(o, to_py_func(i)))
+static CYTHON_INLINE PyObject *__Pyx_GetItemInt_Tuple_Fast(PyObject *o, Py_ssize_t i) {
+    if (likely(o != Py_None)) {
+        if (likely((0 <= i) & (i < PyTuple_GET_SIZE(o)))) {
+            PyObject *r = PyTuple_GET_ITEM(o, i);
+            Py_INCREF(r);
+            return r;
+        }
+        else if ((-PyTuple_GET_SIZE(o) <= i) & (i < 0)) {
+            PyObject *r = PyTuple_GET_ITEM(o, PyTuple_GET_SIZE(o) + i);
+            Py_INCREF(r);
+            return r;
+        }
+    }
+    return __Pyx_GetItemInt_Generic(o, PyInt_FromSsize_t(i));
+}
+#define __Pyx_GetItemInt(o, i, size, to_py_func) (((size) <= sizeof(Py_ssize_t)) ? \
+                                                    __Pyx_GetItemInt_Fast(o, i) : \
+                                                    __Pyx_GetItemInt_Generic(o, to_py_func(i)))
+static CYTHON_INLINE PyObject *__Pyx_GetItemInt_Fast(PyObject *o, Py_ssize_t i) {
+    if (PyList_CheckExact(o)) {
+        Py_ssize_t n = (likely(i >= 0)) ? i : i + PyList_GET_SIZE(o);
+        if (likely((n >= 0) & (n < PyList_GET_SIZE(o)))) {
+            PyObject *r = PyList_GET_ITEM(o, n);
+            Py_INCREF(r);
+            return r;
+        }
+    }
+    else if (PyTuple_CheckExact(o)) {
+        Py_ssize_t n = (likely(i >= 0)) ? i : i + PyTuple_GET_SIZE(o);
+        if (likely((n >= 0) & (n < PyTuple_GET_SIZE(o)))) {
+            PyObject *r = PyTuple_GET_ITEM(o, n);
+            Py_INCREF(r);
+            return r;
+        }
+    }
+    else if (likely(i >= 0)) {
+        PySequenceMethods *m = Py_TYPE(o)->tp_as_sequence;
+        if (likely(m && m->sq_item)) {
+            return m->sq_item(o, i);
+        }
+    }
+    return __Pyx_GetItemInt_Generic(o, PyInt_FromSsize_t(i));
+}
+
 static double __Pyx__PyObject_AsDouble(PyObject* obj); /* proto */
 #define __Pyx_PyObject_AsDouble(obj) \
 ((likely(PyFloat_CheckExact(obj))) ? \
@@ -693,6 +827,10 @@ static int __Pyx_InitStrings(__Pyx_StringTabEntry *t); /*proto*/
 
 /* Module declarations from 'libcpp.vector' */
 
+/* Module declarations from 'libcpp.utility' */
+
+/* Module declarations from 'libcpp.pair' */
+
 /* Module declarations from 'utils' */
 
 /* Module declarations from 'lattice' */
@@ -704,14 +842,17 @@ static int __Pyx_InitStrings(__Pyx_StringTabEntry *t); /*proto*/
 /* Module declarations from 'kbest' */
 
 /* Module declarations from '_cdec' */
-static PyTypeObject *__pyx_ptype_5_cdec_Weights = 0;
-static PyTypeObject *__pyx_ptype_5_cdec_Decoder = 0;
+static PyTypeObject *__pyx_ptype_5_cdec_DenseVector = 0;
+static PyTypeObject *__pyx_ptype_5_cdec_SparseVector = 0;
 static PyTypeObject *__pyx_ptype_5_cdec_Hypergraph = 0;
 static PyTypeObject *__pyx_ptype_5_cdec_Lattice = 0;
+static PyTypeObject *__pyx_ptype_5_cdec_Decoder = 0;
 static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct____iter__ = 0;
-static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_1_kbest = 0;
-static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_2_kbest_tree = 0;
-static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_3_sample = 0;
+static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_1___iter__ = 0;
+static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_2_kbest = 0;
+static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_3_kbest_tree = 0;
+static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_4_sample = 0;
+static PyTypeObject *__pyx_ptype_5_cdec___pyx_scope_struct_5___iter__ = 0;
 #define __Pyx_MODULE_NAME "_cdec"
 int __pyx_module_is_main__cdec = 0;
 
@@ -719,12 +860,53 @@ int __pyx_module_is_main__cdec = 0;
 static PyObject *__pyx_builtin_Exception;
 static PyObject *__pyx_builtin_KeyError;
 static PyObject *__pyx_builtin_range;
-static PyObject *__pyx_builtin_open;
+static PyObject *__pyx_builtin_ValueError;
+static PyObject *__pyx_builtin_NotImplemented;
 static PyObject *__pyx_builtin_eval;
-static int __pyx_pf_5_cdec_7Weights___cinit__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self, struct __pyx_obj_5_cdec_Decoder *__pyx_v_decoder); /* proto */
-static PyObject *__pyx_pf_5_cdec_7Weights_2__getitem__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self, char *__pyx_v_fname); /* proto */
-static int __pyx_pf_5_cdec_7Weights_4__setitem__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self, char *__pyx_v_fname, float __pyx_v_value); /* proto */
-static PyObject *__pyx_pf_5_cdec_7Weights_6__iter__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self); /* proto */
+static PyObject *__pyx_builtin_enumerate;
+static PyObject *__pyx_builtin_TypeError;
+static PyObject *__pyx_builtin_IndexError;
+static PyObject *__pyx_builtin_open;
+static PyObject *__pyx_pf_5_cdec_11DenseVector___getitem__(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self, char *__pyx_v_fname); /* proto */
+static int __pyx_pf_5_cdec_11DenseVector_2__setitem__(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self, char *__pyx_v_fname, float __pyx_v_value); /* proto */
+static PyObject *__pyx_pf_5_cdec_11DenseVector_4__iter__(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_11DenseVector_7dot(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other); /* proto */
+static PyObject *__pyx_pf_5_cdec_11DenseVector_9tosparse(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector___getitem__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, char *__pyx_v_fname); /* proto */
+static int __pyx_pf_5_cdec_12SparseVector_2__setitem__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, char *__pyx_v_fname, float __pyx_v_value); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_4__iter__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_7dot(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, PyObject *__pyx_v_other); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_9todense(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_11__richcmp__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other, int __pyx_v_op); /* proto */
+static Py_ssize_t __pyx_pf_5_cdec_12SparseVector_13__len__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self); /* proto */
+static int __pyx_pf_5_cdec_12SparseVector_15__contains__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, char *__pyx_v_fname); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_17__iadd__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_19__isub__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_21__imul__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, float __pyx_v_scalar); /* proto */
+#if PY_MAJOR_VERSION < 3
+static PyObject *__pyx_pf_5_cdec_12SparseVector_23__idiv__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, float __pyx_v_scalar); /* proto */
+#endif
+static PyObject *__pyx_pf_5_cdec_12SparseVector_25__add__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other); /* proto */
+static PyObject *__pyx_pf_5_cdec_12SparseVector_27__sub__(struct __pyx_obj_5_cdec_SparseVector *__pyx_v_self, struct __pyx_obj_5_cdec_SparseVector *__pyx_v_other); /* proto */
+static void __pyx_pf_5_cdec_10Hypergraph___dealloc__(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_2viterbi(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_4viterbi_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_6viterbi_source_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_8viterbi_features(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_10kbest(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_13kbest_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_16sample(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, unsigned int __pyx_v_n); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_19intersect(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, struct __pyx_obj_5_cdec_Lattice *__pyx_v_lat); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_21prune(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_beam_alpha, PyObject *__pyx_v_density, PyObject *__pyx_v_kwargs); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_23lattice(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_25reweight(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_weights); /* proto */
+static int __pyx_pf_5_cdec_7Lattice___init__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self, PyObject *__pyx_v_inp); /* proto */
+static PyObject *__pyx_pf_5_cdec_7Lattice_2__getitem__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self, int __pyx_v_index); /* proto */
+static int __pyx_pf_5_cdec_7Lattice_4__setitem__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self, int __pyx_v_index, PyObject *__pyx_v_arcs); /* proto */
+static Py_ssize_t __pyx_pf_5_cdec_7Lattice_6__len__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_7Lattice_8__str__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
+static PyObject *__pyx_pf_5_cdec_7Lattice_10__iter__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
+static void __pyx_pf_5_cdec_7Lattice_13__dealloc__(CYTHON_UNUSED struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
 static int __pyx_pf_5_cdec_7Decoder___cinit__(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self, char *__pyx_v_config); /* proto */
 static void __pyx_pf_5_cdec_7Decoder_2__dealloc__(CYTHON_UNUSED struct __pyx_obj_5_cdec_Decoder *__pyx_v_self); /* proto */
 static PyObject *__pyx_pf_5_cdec_7Decoder_4read_weights(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self, PyObject *__pyx_v_cfg); /* proto */
@@ -732,17 +914,16 @@ static PyObject *__pyx_pf_5_cdec_7Decoder_6translate(struct __pyx_obj_5_cdec_Dec
 static PyObject *__pyx_pf_5_cdec_7Decoder_7weights___get__(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self); /* proto */
 static int __pyx_pf_5_cdec_7Decoder_7weights_2__set__(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self, PyObject *__pyx_v_value); /* proto */
 static int __pyx_pf_5_cdec_7Decoder_7weights_4__del__(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self); /* proto */
-static void __pyx_pf_5_cdec_10Hypergraph___dealloc__(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_2viterbi(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_4viterbi_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_6kbest(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_9kbest_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_12intersect(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, struct __pyx_obj_5_cdec_Lattice *__pyx_v_lat); /* proto */
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_14sample(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, unsigned int __pyx_v_n); /* proto */
-static int __pyx_pf_5_cdec_7Lattice___init__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self, PyObject *__pyx_v_plf_tuple); /* proto */
-static PyObject *__pyx_pf_5_cdec_7Lattice_2__str__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
-static PyObject *__pyx_pf_5_cdec_7Lattice_4__iter__(struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
-static void __pyx_pf_5_cdec_7Lattice_6__dealloc__(CYTHON_UNUSED struct __pyx_obj_5_cdec_Lattice *__pyx_v_self); /* proto */
+static char __pyx_k_1[] = "cannot take the dot product of %s and SparseVector";
+static char __pyx_k_2[] = "comparison not implemented for SparseVector";
+static char __pyx_k_10[] = "csplit_preserve_full_word";
+static char __pyx_k_11[] = "cannot reweight hypergraph with %s";
+static char __pyx_k_13[] = "Cannot create lattice from %s";
+static char __pyx_k_14[] = "lattice index out of range";
+static char __pyx_k_21[] = "Cannot translate input type %s";
+static char __pyx_k__dot[] = "dot";
+static char __pyx_k__inp[] = "inp";
+static char __pyx_k__plf[] = "plf";
 static char __pyx_k__eval[] = "eval";
 static char __pyx_k__open[] = "open";
 static char __pyx_k__self[] = "self";
@@ -754,7 +935,7 @@ static char __pyx_k__strip[] = "strip";
 static char __pyx_k__config[] = "config";
 static char __pyx_k__decode[] = "decode";
 static char __pyx_k__encode[] = "encode";
-static char __pyx_k__decoder[] = "decoder";
+static char __pyx_k__density[] = "density";
 static char __pyx_k__grammar[] = "grammar";
 static char __pyx_k__KeyError[] = "KeyError";
 static char __pyx_k____exit__[] = "__exit__";
@@ -762,149 +943,98 @@ static char __pyx_k____main__[] = "__main__";
 static char __pyx_k____test__[] = "__test__";
 static char __pyx_k__sentence[] = "sentence";
 static char __pyx_k__Exception[] = "Exception";
+static char __pyx_k__TypeError[] = "TypeError";
 static char __pyx_k____enter__[] = "__enter__";
-static char __pyx_k__plf_tuple[] = "plf_tuple";
+static char __pyx_k__enumerate[] = "enumerate";
+static char __pyx_k__IndexError[] = "IndexError";
+static char __pyx_k__ValueError[] = "ValueError";
+static char __pyx_k__beam_alpha[] = "beam_alpha";
 static char __pyx_k__ParseFailed[] = "ParseFailed";
+static char __pyx_k__NotImplemented[] = "NotImplemented";
+static PyObject *__pyx_kp_s_1;
+static PyObject *__pyx_n_s_10;
+static PyObject *__pyx_kp_s_11;
+static PyObject *__pyx_kp_s_13;
+static PyObject *__pyx_kp_s_14;
+static PyObject *__pyx_kp_s_2;
+static PyObject *__pyx_kp_s_21;
 static PyObject *__pyx_n_s__Exception;
+static PyObject *__pyx_n_s__IndexError;
 static PyObject *__pyx_n_s__KeyError;
+static PyObject *__pyx_n_s__NotImplemented;
 static PyObject *__pyx_n_s__ParseFailed;
+static PyObject *__pyx_n_s__TypeError;
+static PyObject *__pyx_n_s__ValueError;
 static PyObject *__pyx_n_s____enter__;
 static PyObject *__pyx_n_s____exit__;
 static PyObject *__pyx_n_s____main__;
 static PyObject *__pyx_n_s____test__;
 static PyObject *__pyx_n_s___cdec;
+static PyObject *__pyx_n_s__beam_alpha;
 static PyObject *__pyx_n_s__config;
 static PyObject *__pyx_n_s__decode;
-static PyObject *__pyx_n_s__decoder;
+static PyObject *__pyx_n_s__density;
+static PyObject *__pyx_n_s__dot;
 static PyObject *__pyx_n_s__encode;
+static PyObject *__pyx_n_s__enumerate;
 static PyObject *__pyx_n_s__eval;
 static PyObject *__pyx_n_s__grammar;
+static PyObject *__pyx_n_s__inp;
 static PyObject *__pyx_n_s__open;
-static PyObject *__pyx_n_s__plf_tuple;
+static PyObject *__pyx_n_s__plf;
 static PyObject *__pyx_n_s__range;
 static PyObject *__pyx_n_s__self;
 static PyObject *__pyx_n_s__sentence;
 static PyObject *__pyx_n_s__split;
 static PyObject *__pyx_n_s__strip;
 static PyObject *__pyx_n_s__utf8;
-static PyObject *__pyx_k_tuple_1;
-static PyObject *__pyx_k_tuple_2;
+static PyObject *__pyx_int_0;
+static PyObject *__pyx_int_1;
 static PyObject *__pyx_k_tuple_3;
 static PyObject *__pyx_k_tuple_4;
 static PyObject *__pyx_k_tuple_5;
 static PyObject *__pyx_k_tuple_6;
 static PyObject *__pyx_k_tuple_7;
+static PyObject *__pyx_k_tuple_8;
+static PyObject *__pyx_k_tuple_9;
+static PyObject *__pyx_k_tuple_12;
+static PyObject *__pyx_k_tuple_15;
+static PyObject *__pyx_k_tuple_16;
+static PyObject *__pyx_k_tuple_17;
+static PyObject *__pyx_k_tuple_18;
+static PyObject *__pyx_k_tuple_19;
+static PyObject *__pyx_k_tuple_20;
 
 /* Python wrapper */
-static int __pyx_pw_5_cdec_7Weights_1__cinit__(PyObject *__pyx_v_self, PyObject *__pyx_args, PyObject *__pyx_kwds); /*proto*/
-static int __pyx_pw_5_cdec_7Weights_1__cinit__(PyObject *__pyx_v_self, PyObject *__pyx_args, PyObject *__pyx_kwds) {
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-static int __pyx_pf_5_cdec_7Weights___cinit__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self, struct __pyx_obj_5_cdec_Decoder *__pyx_v_decoder) {
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- *     def __getitem__(self, char* fname):
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-static PyObject *__pyx_pw_5_cdec_7Weights_3__getitem__(PyObject *__pyx_v_self, PyObject *__pyx_arg_fname) {
+static PyObject *__pyx_pw_5_cdec_11DenseVector_1__getitem__(PyObject *__pyx_v_self, PyObject *__pyx_arg_fname); /*proto*/
+static PyObject *__pyx_pw_5_cdec_11DenseVector_1__getitem__(PyObject *__pyx_v_self, PyObject *__pyx_arg_fname) {
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-  __Pyx_AddTraceback("_cdec.Weights.__getitem__", __pyx_clineno, __pyx_lineno, __pyx_filename);
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-/* "_cdec.pyx":21
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+/* "/Users/vchahun/Sandbox/cdec/python/src/vectors.pxi":6
+ *     cdef vector[weight_t]* vector
  * 
  *     def __getitem__(self, char* fname):             # <<<<<<<<<<<<<<
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- *         if fid <= self.weights.size():
+ *         if fid <= self.vector.size():
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-static PyObject *__pyx_pf_5_cdec_7Weights_2__getitem__(struct __pyx_obj_5_cdec_Weights *__pyx_v_self, char *__pyx_v_fname) {
+static PyObject *__pyx_pf_5_cdec_11DenseVector___getitem__(struct __pyx_obj_5_cdec_DenseVector *__pyx_v_self, char *__pyx_v_fname) {
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-  /* "_cdec.pyx":23
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+  __pyx_cur_scope = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)__pyx_ptype_5_cdec___pyx_scope_struct_2_kbest->tp_new(__pyx_ptype_5_cdec___pyx_scope_struct_2_kbest, __pyx_empty_tuple, NULL);
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@@ -2294,7 +3017,7 @@ static PyObject *__pyx_pf_5_cdec_10Hypergraph_6kbest(struct __pyx_obj_5_cdec_Hyp
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+    __pyx_GeneratorObject *gen = __Pyx_Generator_New((__pyx_generator_body_t) __pyx_gb_5_cdec_10Hypergraph_12generator2, (PyObject *) __pyx_cur_scope); if (unlikely(!gen)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 32; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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   return __pyx_r;
 }
 
-static PyObject *__pyx_gb_5_cdec_10Hypergraph_8generator1(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value) /* generator body */
+static PyObject *__pyx_gb_5_cdec_10Hypergraph_12generator2(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value) /* generator body */
 {
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+  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *__pyx_cur_scope = ((struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)__pyx_generator->closure);
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   unsigned int __pyx_t_1;
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-  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 92; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 32; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
 
-  /* "_cdec.pyx":93
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- *         cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal].Derivation* derivation
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-    {__pyx_filename = __pyx_f[0]; __pyx_lineno = 93; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  }
-  #endif
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-  /* "_cdec.pyx":94
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- *         cdef str tree
+ *         cdef str sentence
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-  __pyx_t_1 = __Pyx_PyInt_AsUnsignedInt(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_1 == (unsigned int)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 94; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_t_1 = __Pyx_PyInt_AsUnsignedInt(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_1 == (unsigned int)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 33; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-  /* "_cdec.pyx":98
- *         cdef str tree
+  /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":37
+ *         cdef str sentence
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-  __pyx_t_2 = __Pyx_PyInt_AsLong(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_2 == (long)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 98; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_t_2 = __Pyx_PyInt_AsLong(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_2 == (long)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 37; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-    /* "_cdec.pyx":99
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":38
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+ *             sentence = GetString(derivation._yield).c_str()
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-    /* "_cdec.pyx":100
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- *             yield tree.decode('utf8')
+ *             sentence = GetString(derivation._yield).c_str()
+ *             yield sentence.decode('utf8')
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     __pyx_t_3 = (!(__pyx_cur_scope->__pyx_v_derivation != 0));
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@@ -2391,32 +3100,32 @@ static PyObject *__pyx_gb_5_cdec_10Hypergraph_8generator1(__pyx_GeneratorObject
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-    /* "_cdec.pyx":101
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+    __pyx_t_4 = PyBytes_FromString(TD::GetString(__pyx_cur_scope->__pyx_v_derivation->yield).c_str()); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 40; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-    if (!(likely(PyString_CheckExact(((PyObject *)__pyx_t_4)))||(PyErr_Format(PyExc_TypeError, "Expected str, got %.200s", Py_TYPE(((PyObject *)__pyx_t_4))->tp_name), 0))) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 101; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-    __Pyx_XGOTREF(((PyObject *)__pyx_cur_scope->__pyx_v_tree));
-    __Pyx_XDECREF(((PyObject *)__pyx_cur_scope->__pyx_v_tree));
+    if (!(likely(PyString_CheckExact(((PyObject *)__pyx_t_4)))||(PyErr_Format(PyExc_TypeError, "Expected str, got %.200s", Py_TYPE(((PyObject *)__pyx_t_4))->tp_name), 0))) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 40; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    __Pyx_XGOTREF(((PyObject *)__pyx_cur_scope->__pyx_v_sentence));
+    __Pyx_XDECREF(((PyObject *)__pyx_cur_scope->__pyx_v_sentence));
     __Pyx_GIVEREF(((PyObject *)__pyx_t_4));
-    __pyx_cur_scope->__pyx_v_tree = ((PyObject*)__pyx_t_4);
+    __pyx_cur_scope->__pyx_v_sentence = ((PyObject*)__pyx_t_4);
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-    /* "_cdec.pyx":102
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":41
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- *             yield tree.decode('utf8')             # <<<<<<<<<<<<<<
+ *             sentence = GetString(derivation._yield).c_str()
+ *             yield sentence.decode('utf8')             # <<<<<<<<<<<<<<
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-    __pyx_t_4 = PyObject_GetAttr(((PyObject *)__pyx_cur_scope->__pyx_v_tree), __pyx_n_s__decode); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 102; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    __pyx_t_4 = PyObject_GetAttr(((PyObject *)__pyx_cur_scope->__pyx_v_sentence), __pyx_n_s__decode); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 41; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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+    __pyx_t_5 = PyObject_Call(__pyx_t_4, ((PyObject *)__pyx_k_tuple_7), NULL); if (unlikely(!__pyx_t_5)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 41; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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     __pyx_t_1 = __pyx_cur_scope->__pyx_t_0;
     __pyx_t_2 = __pyx_cur_scope->__pyx_t_1;
-    if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 102; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 41; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
   }
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-  /* "_cdec.pyx":103
- *             tree = GetString(derivation._yield).c_str()
- *             yield tree.decode('utf8')
+  /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":42
+ *             sentence = GetString(derivation._yield).c_str()
+ *             yield sentence.decode('utf8')
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  *     def kbest_tree(self, size):
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+static PyObject *__pyx_gb_5_cdec_10Hypergraph_15generator3(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value); /* proto */
 
 /* Python wrapper */
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-static PyObject *__pyx_pw_5_cdec_10Hypergraph_10kbest_tree(PyObject *__pyx_v_self, PyObject *__pyx_v_size) {
+static PyObject *__pyx_pw_5_cdec_10Hypergraph_14kbest_tree(PyObject *__pyx_v_self, PyObject *__pyx_v_size); /*proto*/
+static PyObject *__pyx_pw_5_cdec_10Hypergraph_14kbest_tree(PyObject *__pyx_v_self, PyObject *__pyx_v_size) {
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+  __pyx_r = __pyx_pf_5_cdec_10Hypergraph_13kbest_tree(((struct __pyx_obj_5_cdec_Hypergraph *)__pyx_v_self), ((PyObject *)__pyx_v_size));
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-/* "_cdec.pyx":105
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  *         cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ETreeTraversal](self.hg[0], size)
+ *         cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal].Derivation* derivation
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-static PyObject *__pyx_pf_5_cdec_10Hypergraph_9kbest_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *__pyx_cur_scope;
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_13kbest_tree(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, PyObject *__pyx_v_size) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *__pyx_cur_scope;
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+  __pyx_cur_scope = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)__pyx_ptype_5_cdec___pyx_scope_struct_3_kbest_tree->tp_new(__pyx_ptype_5_cdec___pyx_scope_struct_3_kbest_tree, __pyx_empty_tuple, NULL);
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+static PyObject *__pyx_gb_5_cdec_10Hypergraph_15generator3(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value) /* generator body */
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+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *__pyx_cur_scope = ((struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)__pyx_generator->closure);
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@@ -2534,58 +3243,44 @@ static PyObject *__pyx_gb_5_cdec_10Hypergraph_11generator2(__pyx_GeneratorObject
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-  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 105; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 44; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
 
-  /* "_cdec.pyx":106
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-  #ifndef CYTHON_WITHOUT_ASSERTIONS
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-  #endif
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-  /* "_cdec.pyx":107
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- *         cdef str sentence
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-  __pyx_t_1 = __Pyx_PyInt_AsUnsignedInt(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_1 == (unsigned int)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 107; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_t_1 = __Pyx_PyInt_AsUnsignedInt(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_1 == (unsigned int)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 45; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-  /* "_cdec.pyx":111
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+  /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":49
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+  __pyx_t_2 = __Pyx_PyInt_AsLong(__pyx_cur_scope->__pyx_v_size); if (unlikely((__pyx_t_2 == (long)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 49; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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     __pyx_cur_scope->__pyx_v_k = __pyx_t_1;
 
-    /* "_cdec.pyx":112
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  *             if not derivation: break
- *             sentence = GetString(derivation._yield).c_str()
+ *             tree = GetString(derivation._yield).c_str()
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-    /* "_cdec.pyx":113
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":51
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  *             if not derivation: break             # <<<<<<<<<<<<<<
- *             sentence = GetString(derivation._yield).c_str()
- *             yield sentence.decode('utf8')
+ *             tree = GetString(derivation._yield).c_str()
+ *             yield tree.decode('utf8')
  */
     __pyx_t_3 = (!(__pyx_cur_scope->__pyx_v_derivation != 0));
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@@ -2594,32 +3289,32 @@ static PyObject *__pyx_gb_5_cdec_10Hypergraph_11generator2(__pyx_GeneratorObject
     }
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-    /* "_cdec.pyx":114
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":52
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  *             if not derivation: break
- *             sentence = GetString(derivation._yield).c_str()             # <<<<<<<<<<<<<<
- *             yield sentence.decode('utf8')
+ *             tree = GetString(derivation._yield).c_str()             # <<<<<<<<<<<<<<
+ *             yield tree.decode('utf8')
  *         del derivations
  */
-    __pyx_t_4 = PyBytes_FromString(TD::GetString(__pyx_cur_scope->__pyx_v_derivation->yield).c_str()); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 114; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    __pyx_t_4 = PyBytes_FromString(TD::GetString(__pyx_cur_scope->__pyx_v_derivation->yield).c_str()); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 52; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-    if (!(likely(PyString_CheckExact(((PyObject *)__pyx_t_4)))||(PyErr_Format(PyExc_TypeError, "Expected str, got %.200s", Py_TYPE(((PyObject *)__pyx_t_4))->tp_name), 0))) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 114; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-    __Pyx_XGOTREF(((PyObject *)__pyx_cur_scope->__pyx_v_sentence));
-    __Pyx_XDECREF(((PyObject *)__pyx_cur_scope->__pyx_v_sentence));
+    if (!(likely(PyString_CheckExact(((PyObject *)__pyx_t_4)))||(PyErr_Format(PyExc_TypeError, "Expected str, got %.200s", Py_TYPE(((PyObject *)__pyx_t_4))->tp_name), 0))) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 52; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    __Pyx_XGOTREF(((PyObject *)__pyx_cur_scope->__pyx_v_tree));
+    __Pyx_XDECREF(((PyObject *)__pyx_cur_scope->__pyx_v_tree));
     __Pyx_GIVEREF(((PyObject *)__pyx_t_4));
-    __pyx_cur_scope->__pyx_v_sentence = ((PyObject*)__pyx_t_4);
+    __pyx_cur_scope->__pyx_v_tree = ((PyObject*)__pyx_t_4);
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-    /* "_cdec.pyx":115
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":53
  *             if not derivation: break
- *             sentence = GetString(derivation._yield).c_str()
- *             yield sentence.decode('utf8')             # <<<<<<<<<<<<<<
+ *             tree = GetString(derivation._yield).c_str()
+ *             yield tree.decode('utf8')             # <<<<<<<<<<<<<<
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  * 
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-    __pyx_t_4 = PyObject_GetAttr(((PyObject *)__pyx_cur_scope->__pyx_v_sentence), __pyx_n_s__decode); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 115; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+    __pyx_t_4 = PyObject_GetAttr(((PyObject *)__pyx_cur_scope->__pyx_v_tree), __pyx_n_s__decode); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 53; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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+    __pyx_t_5 = PyObject_Call(__pyx_t_4, ((PyObject *)__pyx_k_tuple_8), NULL); if (unlikely(!__pyx_t_5)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 53; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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-    if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 115; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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+ *             yield tree.decode('utf8')
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- *     def intersect(self, Lattice lat):
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 /* Python wrapper */
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-  /* "_cdec.pyx":120
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- *     def sample(self, unsigned n):
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-  HG::Intersect((__pyx_v_lat->lattice[0]), __pyx_v_self->hg);
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-/* Python wrapper */
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+static PyObject *__pyx_pw_5_cdec_10Hypergraph_17sample(PyObject *__pyx_v_self, PyObject *__pyx_arg_n); /*proto*/
+static PyObject *__pyx_pw_5_cdec_10Hypergraph_17sample(PyObject *__pyx_v_self, PyObject *__pyx_arg_n) {
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+    __pyx_v_n = __Pyx_PyInt_AsUnsignedInt(__pyx_arg_n); if (unlikely((__pyx_v_n == (unsigned int)-1) && PyErr_Occurred())) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 56; __pyx_clineno = __LINE__; goto __pyx_L3_error;}
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+  __pyx_r = __pyx_pf_5_cdec_10Hypergraph_16sample(((struct __pyx_obj_5_cdec_Hypergraph *)__pyx_v_self), ((unsigned int)__pyx_v_n));
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-/* "_cdec.pyx":122
- *         hypergraph.Intersect(lat.lattice[0], self.hg)
+/* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":56
+ *         del derivations
  * 
  *     def sample(self, unsigned n):             # <<<<<<<<<<<<<<
- *         assert (self.hg != NULL)
  *         cdef vector[hypergraph.Hypothesis]* hypos = new vector[hypergraph.Hypothesis]()
+ *         if self.rng == NULL:
  */
 
-static PyObject *__pyx_pf_5_cdec_10Hypergraph_14sample(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, unsigned int __pyx_v_n) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *__pyx_cur_scope;
+static PyObject *__pyx_pf_5_cdec_10Hypergraph_16sample(struct __pyx_obj_5_cdec_Hypergraph *__pyx_v_self, unsigned int __pyx_v_n) {
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+  __pyx_cur_scope = (struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)__pyx_ptype_5_cdec___pyx_scope_struct_4_sample->tp_new(__pyx_ptype_5_cdec___pyx_scope_struct_4_sample, __pyx_empty_tuple, NULL);
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+    __pyx_GeneratorObject *gen = __Pyx_Generator_New((__pyx_generator_body_t) __pyx_gb_5_cdec_10Hypergraph_18generator4, (PyObject *) __pyx_cur_scope); if (unlikely(!gen)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 56; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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 }
 
-static PyObject *__pyx_gb_5_cdec_10Hypergraph_16generator3(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value) /* generator body */
+static PyObject *__pyx_gb_5_cdec_10Hypergraph_18generator4(__pyx_GeneratorObject *__pyx_generator, PyObject *__pyx_sent_value) /* generator body */
 {
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+  struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *__pyx_cur_scope = ((struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)__pyx_generator->closure);
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   int __pyx_t_1;
   size_t __pyx_t_2;
@@ -2811,33 +3440,19 @@ static PyObject *__pyx_gb_5_cdec_10Hypergraph_16generator3(__pyx_GeneratorObject
     return NULL;
   }
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-  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 122; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (unlikely(!__pyx_sent_value)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 56; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
 
-  /* "_cdec.pyx":123
+  /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":57
  * 
  *     def sample(self, unsigned n):
- *         assert (self.hg != NULL)             # <<<<<<<<<<<<<<
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- *         if self.rng == NULL:
- */
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-    {__pyx_filename = __pyx_f[0]; __pyx_lineno = 123; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  }
-  #endif
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-  /* "_cdec.pyx":124
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   __pyx_cur_scope->__pyx_v_hypos = new std::vector<HypergraphSampler::Hypothesis>();
 
-  /* "_cdec.pyx":125
- *         assert (self.hg != NULL)
+  /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":58
+ *     def sample(self, unsigned n):
  *         cdef vector[hypergraph.Hypothesis]* hypos = new vector[hypergraph.Hypothesis]()
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@@ -2846,7 +3461,7 @@ static PyObject *__pyx_gb_5_cdec_10Hypergraph_16generator3(__pyx_GeneratorObject
   __pyx_t_1 = (__pyx_cur_scope->__pyx_v_self->rng == NULL);
   if (__pyx_t_1) {
 
-    /* "_cdec.pyx":126
+    /* "/Users/vchahun/Sandbox/cdec/python/src/hypergraph.pxi":59
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-  /* "_cdec.pyx":127
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-    /* "_cdec.pyx":131
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+    __pyx_t_4 = PyBytes_FromString(TD::GetString(((__pyx_cur_scope->__pyx_v_hypos[0])[__pyx_cur_scope->__pyx_v_k]).words).c_str()); if (unlikely(!__pyx_t_4)) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 64; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
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+ */
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+ */
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+  /* "_cdec.pyx":53
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+  __Pyx_XDECREF(__pyx_t_3);
+  __Pyx_AddTraceback("_cdec.Decoder.translate", __pyx_clineno, __pyx_lineno, __pyx_filename);
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+  __pyx_L0:;
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+  __Pyx_XDECREF((PyObject *)__pyx_v_hg);
+  __Pyx_XGIVEREF(__pyx_r);
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+/* Python wrapper */
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+ */
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+  __pyx_r = 0;
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+static int __pyx_pf_5_cdec_7Decoder_7weights_4__del__(struct __pyx_obj_5_cdec_Decoder *__pyx_v_self) {
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+  __pyx_v_self->weights = ((struct __pyx_obj_5_cdec_DenseVector *)Py_None);
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+  __pyx_r = 0;
+  __Pyx_RefNannyFinishContext();
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+}
+
+static PyObject *__pyx_tp_new_5_cdec_DenseVector(PyTypeObject *t, PyObject *a, PyObject *k) {
   PyObject *o = (*t->tp_alloc)(t, 0);
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-    Py_DECREF(o); o = 0;
-  }
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 }
 
-static void __pyx_tp_dealloc_5_cdec_Weights(PyObject *o) {
+static void __pyx_tp_dealloc_5_cdec_DenseVector(PyObject *o) {
   (*Py_TYPE(o)->tp_free)(o);
 }
-static PyObject *__pyx_sq_item_5_cdec_Weights(PyObject *o, Py_ssize_t i) {
+static PyObject *__pyx_sq_item_5_cdec_DenseVector(PyObject *o, Py_ssize_t i) {
   PyObject *r;
   PyObject *x = PyInt_FromSsize_t(i); if(!x) return 0;
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@@ -3263,9 +5856,9 @@ static PyObject *__pyx_sq_item_5_cdec_Weights(PyObject *o, Py_ssize_t i) {
   return r;
 }
 
-static int __pyx_mp_ass_subscript_5_cdec_Weights(PyObject *o, PyObject *i, PyObject *v) {
+static int __pyx_mp_ass_subscript_5_cdec_DenseVector(PyObject *o, PyObject *i, PyObject *v) {
   if (v) {
-    return __pyx_pw_5_cdec_7Weights_5__setitem__(o, i, v);
+    return __pyx_pw_5_cdec_11DenseVector_3__setitem__(o, i, v);
   }
   else {
     PyErr_Format(PyExc_NotImplementedError,
@@ -3274,11 +5867,13 @@ static int __pyx_mp_ass_subscript_5_cdec_Weights(PyObject *o, PyObject *i, PyObj
   }
 }
 
-static PyMethodDef __pyx_methods_5_cdec_Weights[] = {
+static PyMethodDef __pyx_methods_5_cdec_DenseVector[] = {
+  {__Pyx_NAMESTR("dot"), (PyCFunction)__pyx_pw_5_cdec_11DenseVector_8dot, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("tosparse"), (PyCFunction)__pyx_pw_5_cdec_11DenseVector_10tosparse, METH_NOARGS, __Pyx_DOCSTR(0)},
   {0, 0, 0, 0}
 };
 
-static PyNumberMethods __pyx_tp_as_number_Weights = {
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   0, /*nb_subtract*/
   0, /*nb_multiply*/
@@ -3336,11 +5931,11 @@ static PyNumberMethods __pyx_tp_as_number_Weights = {
   #endif
 };
 
-static PySequenceMethods __pyx_tp_as_sequence_Weights = {
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   0, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
-  __pyx_sq_item_5_cdec_Weights, /*sq_item*/
+  __pyx_sq_item_5_cdec_DenseVector, /*sq_item*/
   0, /*sq_slice*/
   0, /*sq_ass_item*/
   0, /*sq_ass_slice*/
@@ -3349,13 +5944,13 @@ static PySequenceMethods __pyx_tp_as_sequence_Weights = {
   0, /*sq_inplace_repeat*/
 };
 
-static PyMappingMethods __pyx_tp_as_mapping_Weights = {
+static PyMappingMethods __pyx_tp_as_mapping_DenseVector = {
   0, /*mp_length*/
-  __pyx_pw_5_cdec_7Weights_3__getitem__, /*mp_subscript*/
-  __pyx_mp_ass_subscript_5_cdec_Weights, /*mp_ass_subscript*/
+  __pyx_pw_5_cdec_11DenseVector_1__getitem__, /*mp_subscript*/
+  __pyx_mp_ass_subscript_5_cdec_DenseVector, /*mp_ass_subscript*/
 };
 
-static PyBufferProcs __pyx_tp_as_buffer_Weights = {
+static PyBufferProcs __pyx_tp_as_buffer_DenseVector = {
   #if PY_MAJOR_VERSION < 3
   0, /*bf_getreadbuffer*/
   #endif
@@ -3376,12 +5971,12 @@ static PyBufferProcs __pyx_tp_as_buffer_Weights = {
   #endif
 };
 
-static PyTypeObject __pyx_type_5_cdec_Weights = {
+static PyTypeObject __pyx_type_5_cdec_DenseVector = {
   PyVarObject_HEAD_INIT(0, 0)
-  __Pyx_NAMESTR("_cdec.Weights"), /*tp_name*/
-  sizeof(struct __pyx_obj_5_cdec_Weights), /*tp_basicsize*/
+  __Pyx_NAMESTR("_cdec.DenseVector"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec_DenseVector), /*tp_basicsize*/
   0, /*tp_itemsize*/
-  __pyx_tp_dealloc_5_cdec_Weights, /*tp_dealloc*/
+  __pyx_tp_dealloc_5_cdec_DenseVector, /*tp_dealloc*/
   0, /*tp_print*/
   0, /*tp_getattr*/
   0, /*tp_setattr*/
@@ -3391,24 +5986,24 @@ static PyTypeObject __pyx_type_5_cdec_Weights = {
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   #endif
   0, /*tp_repr*/
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-  &__pyx_tp_as_sequence_Weights, /*tp_as_sequence*/
-  &__pyx_tp_as_mapping_Weights, /*tp_as_mapping*/
+  &__pyx_tp_as_number_DenseVector, /*tp_as_number*/
+  &__pyx_tp_as_sequence_DenseVector, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping_DenseVector, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
   0, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
-  &__pyx_tp_as_buffer_Weights, /*tp_as_buffer*/
+  &__pyx_tp_as_buffer_DenseVector, /*tp_as_buffer*/
   Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_BASETYPE, /*tp_flags*/
   0, /*tp_doc*/
   0, /*tp_traverse*/
   0, /*tp_clear*/
   0, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
-  __pyx_pw_5_cdec_7Weights_7__iter__, /*tp_iter*/
+  __pyx_pw_5_cdec_11DenseVector_5__iter__, /*tp_iter*/
   0, /*tp_iternext*/
-  __pyx_methods_5_cdec_Weights, /*tp_methods*/
+  __pyx_methods_5_cdec_DenseVector, /*tp_methods*/
   0, /*tp_members*/
   0, /*tp_getset*/
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   0, /*tp_init*/
   0, /*tp_alloc*/
-  __pyx_tp_new_5_cdec_Weights, /*tp_new*/
+  __pyx_tp_new_5_cdec_DenseVector, /*tp_new*/
   0, /*tp_free*/
   0, /*tp_is_gc*/
   0, /*tp_bases*/
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 };
 
-static PyObject *__pyx_tp_new_5_cdec_Decoder(PyTypeObject *t, PyObject *a, PyObject *k) {
-  struct __pyx_obj_5_cdec_Decoder *p;
+static PyObject *__pyx_tp_new_5_cdec_SparseVector(PyTypeObject *t, PyObject *a, PyObject *k) {
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   if (!o) return 0;
-  p = ((struct __pyx_obj_5_cdec_Decoder *)o);
-  p->weights = ((struct __pyx_obj_5_cdec_Weights *)Py_None); Py_INCREF(Py_None);
-  if (__pyx_pw_5_cdec_7Decoder_1__cinit__(o, a, k) < 0) {
-    Py_DECREF(o); o = 0;
-  }
   return o;
 }
 
-static void __pyx_tp_dealloc_5_cdec_Decoder(PyObject *o) {
-  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
-  {
-    PyObject *etype, *eval, *etb;
-    PyErr_Fetch(&etype, &eval, &etb);
-    ++Py_REFCNT(o);
-    __pyx_pw_5_cdec_7Decoder_3__dealloc__(o);
-    if (PyErr_Occurred()) PyErr_WriteUnraisable(o);
-    --Py_REFCNT(o);
-    PyErr_Restore(etype, eval, etb);
-  }
-  Py_XDECREF(((PyObject *)p->weights));
+static void __pyx_tp_dealloc_5_cdec_SparseVector(PyObject *o) {
   (*Py_TYPE(o)->tp_free)(o);
 }
-
-static int __pyx_tp_traverse_5_cdec_Decoder(PyObject *o, visitproc v, void *a) {
-  int e;
-  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
-  if (p->weights) {
-    e = (*v)(((PyObject*)p->weights), a); if (e) return e;
-  }
-  return 0;
-}
-
-static int __pyx_tp_clear_5_cdec_Decoder(PyObject *o) {
-  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
-  PyObject* tmp;
-  tmp = ((PyObject*)p->weights);
-  p->weights = ((struct __pyx_obj_5_cdec_Weights *)Py_None); Py_INCREF(Py_None);
-  Py_XDECREF(tmp);
-  return 0;
-}
-
-static PyObject *__pyx_getprop_5_cdec_7Decoder_weights(PyObject *o, void *x) {
-  return __pyx_pw_5_cdec_7Decoder_7weights_1__get__(o);
+static PyObject *__pyx_sq_item_5_cdec_SparseVector(PyObject *o, Py_ssize_t i) {
+  PyObject *r;
+  PyObject *x = PyInt_FromSsize_t(i); if(!x) return 0;
+  r = Py_TYPE(o)->tp_as_mapping->mp_subscript(o, x);
+  Py_DECREF(x);
+  return r;
 }
 
-static int __pyx_setprop_5_cdec_7Decoder_weights(PyObject *o, PyObject *v, void *x) {
+static int __pyx_mp_ass_subscript_5_cdec_SparseVector(PyObject *o, PyObject *i, PyObject *v) {
   if (v) {
-    return __pyx_pw_5_cdec_7Decoder_7weights_3__set__(o, v);
+    return __pyx_pw_5_cdec_12SparseVector_3__setitem__(o, i, v);
   }
   else {
-    return __pyx_pw_5_cdec_7Decoder_7weights_5__del__(o);
+    PyErr_Format(PyExc_NotImplementedError,
+      "Subscript deletion not supported by %s", Py_TYPE(o)->tp_name);
+    return -1;
   }
 }
 
-static PyMethodDef __pyx_methods_5_cdec_Decoder[] = {
-  {__Pyx_NAMESTR("read_weights"), (PyCFunction)__pyx_pw_5_cdec_7Decoder_5read_weights, METH_O, __Pyx_DOCSTR(0)},
-  {__Pyx_NAMESTR("translate"), (PyCFunction)__pyx_pw_5_cdec_7Decoder_7translate, METH_VARARGS|METH_KEYWORDS, __Pyx_DOCSTR(0)},
+static PyMethodDef __pyx_methods_5_cdec_SparseVector[] = {
+  {__Pyx_NAMESTR("dot"), (PyCFunction)__pyx_pw_5_cdec_12SparseVector_8dot, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("todense"), (PyCFunction)__pyx_pw_5_cdec_12SparseVector_10todense, METH_NOARGS, __Pyx_DOCSTR(0)},
   {0, 0, 0, 0}
 };
 
-static struct PyGetSetDef __pyx_getsets_5_cdec_Decoder[] = {
-  {(char *)"weights", __pyx_getprop_5_cdec_7Decoder_weights, __pyx_setprop_5_cdec_7Decoder_weights, 0, 0},
-  {0, 0, 0, 0, 0}
-};
-
-static PyNumberMethods __pyx_tp_as_number_Decoder = {
-  0, /*nb_add*/
-  0, /*nb_subtract*/
+static PyNumberMethods __pyx_tp_as_number_SparseVector = {
+  __pyx_pw_5_cdec_12SparseVector_26__add__, /*nb_add*/
+  __pyx_pw_5_cdec_12SparseVector_28__sub__, /*nb_subtract*/
   0, /*nb_multiply*/
   #if PY_MAJOR_VERSION < 3
   0, /*nb_divide*/
@@ -3537,11 +6097,11 @@ static PyNumberMethods __pyx_tp_as_number_Decoder = {
   #if PY_MAJOR_VERSION < 3
   0, /*nb_hex*/
   #endif
-  0, /*nb_inplace_add*/
-  0, /*nb_inplace_subtract*/
-  0, /*nb_inplace_multiply*/
+  __pyx_pw_5_cdec_12SparseVector_18__iadd__, /*nb_inplace_add*/
+  __pyx_pw_5_cdec_12SparseVector_20__isub__, /*nb_inplace_subtract*/
+  __pyx_pw_5_cdec_12SparseVector_22__imul__, /*nb_inplace_multiply*/
   #if PY_MAJOR_VERSION < 3
-  0, /*nb_inplace_divide*/
+  __pyx_pw_5_cdec_12SparseVector_24__idiv__, /*nb_inplace_divide*/
   #endif
   0, /*nb_inplace_remainder*/
   0, /*nb_inplace_power*/
@@ -3559,26 +6119,26 @@ static PyNumberMethods __pyx_tp_as_number_Decoder = {
   #endif
 };
 
-static PySequenceMethods __pyx_tp_as_sequence_Decoder = {
-  0, /*sq_length*/
+static PySequenceMethods __pyx_tp_as_sequence_SparseVector = {
+  __pyx_pw_5_cdec_12SparseVector_14__len__, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
-  0, /*sq_item*/
+  __pyx_sq_item_5_cdec_SparseVector, /*sq_item*/
   0, /*sq_slice*/
   0, /*sq_ass_item*/
   0, /*sq_ass_slice*/
-  0, /*sq_contains*/
+  __pyx_pw_5_cdec_12SparseVector_16__contains__, /*sq_contains*/
   0, /*sq_inplace_concat*/
   0, /*sq_inplace_repeat*/
 };
 
-static PyMappingMethods __pyx_tp_as_mapping_Decoder = {
-  0, /*mp_length*/
-  0, /*mp_subscript*/
-  0, /*mp_ass_subscript*/
+static PyMappingMethods __pyx_tp_as_mapping_SparseVector = {
+  __pyx_pw_5_cdec_12SparseVector_14__len__, /*mp_length*/
+  __pyx_pw_5_cdec_12SparseVector_1__getitem__, /*mp_subscript*/
+  __pyx_mp_ass_subscript_5_cdec_SparseVector, /*mp_ass_subscript*/
 };
 
-static PyBufferProcs __pyx_tp_as_buffer_Decoder = {
+static PyBufferProcs __pyx_tp_as_buffer_SparseVector = {
   #if PY_MAJOR_VERSION < 3
   0, /*bf_getreadbuffer*/
   #endif
@@ -3599,12 +6159,12 @@ static PyBufferProcs __pyx_tp_as_buffer_Decoder = {
   #endif
 };
 
-static PyTypeObject __pyx_type_5_cdec_Decoder = {
+static PyTypeObject __pyx_type_5_cdec_SparseVector = {
   PyVarObject_HEAD_INIT(0, 0)
-  __Pyx_NAMESTR("_cdec.Decoder"), /*tp_name*/
-  sizeof(struct __pyx_obj_5_cdec_Decoder), /*tp_basicsize*/
+  __Pyx_NAMESTR("_cdec.SparseVector"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec_SparseVector), /*tp_basicsize*/
   0, /*tp_itemsize*/
-  __pyx_tp_dealloc_5_cdec_Decoder, /*tp_dealloc*/
+  __pyx_tp_dealloc_5_cdec_SparseVector, /*tp_dealloc*/
   0, /*tp_print*/
   0, /*tp_getattr*/
   0, /*tp_setattr*/
@@ -3614,26 +6174,26 @@ static PyTypeObject __pyx_type_5_cdec_Decoder = {
   0, /*reserved*/
   #endif
   0, /*tp_repr*/
-  &__pyx_tp_as_number_Decoder, /*tp_as_number*/
-  &__pyx_tp_as_sequence_Decoder, /*tp_as_sequence*/
-  &__pyx_tp_as_mapping_Decoder, /*tp_as_mapping*/
+  &__pyx_tp_as_number_SparseVector, /*tp_as_number*/
+  &__pyx_tp_as_sequence_SparseVector, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping_SparseVector, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
   0, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
-  &__pyx_tp_as_buffer_Decoder, /*tp_as_buffer*/
-  Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_BASETYPE|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+  &__pyx_tp_as_buffer_SparseVector, /*tp_as_buffer*/
+  Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_BASETYPE, /*tp_flags*/
   0, /*tp_doc*/
-  __pyx_tp_traverse_5_cdec_Decoder, /*tp_traverse*/
-  __pyx_tp_clear_5_cdec_Decoder, /*tp_clear*/
-  0, /*tp_richcompare*/
+  0, /*tp_traverse*/
+  0, /*tp_clear*/
+  __pyx_pw_5_cdec_12SparseVector_12__richcmp__, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
-  0, /*tp_iter*/
+  __pyx_pw_5_cdec_12SparseVector_5__iter__, /*tp_iter*/
   0, /*tp_iternext*/
-  __pyx_methods_5_cdec_Decoder, /*tp_methods*/
+  __pyx_methods_5_cdec_SparseVector, /*tp_methods*/
   0, /*tp_members*/
-  __pyx_getsets_5_cdec_Decoder, /*tp_getset*/
+  0, /*tp_getset*/
   0, /*tp_base*/
   0, /*tp_dict*/
   0, /*tp_descr_get*/
@@ -3641,7 +6201,7 @@ static PyTypeObject __pyx_type_5_cdec_Decoder = {
   0, /*tp_dictoffset*/
   0, /*tp_init*/
   0, /*tp_alloc*/
-  __pyx_tp_new_5_cdec_Decoder, /*tp_new*/
+  __pyx_tp_new_5_cdec_SparseVector, /*tp_new*/
   0, /*tp_free*/
   0, /*tp_is_gc*/
   0, /*tp_bases*/
@@ -3677,10 +6237,15 @@ static void __pyx_tp_dealloc_5_cdec_Hypergraph(PyObject *o) {
 static PyMethodDef __pyx_methods_5_cdec_Hypergraph[] = {
   {__Pyx_NAMESTR("viterbi"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_3viterbi, METH_NOARGS, __Pyx_DOCSTR(0)},
   {__Pyx_NAMESTR("viterbi_tree"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_5viterbi_tree, METH_NOARGS, __Pyx_DOCSTR(0)},
-  {__Pyx_NAMESTR("kbest"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_7kbest, METH_O, __Pyx_DOCSTR(0)},
-  {__Pyx_NAMESTR("kbest_tree"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_10kbest_tree, METH_O, __Pyx_DOCSTR(0)},
-  {__Pyx_NAMESTR("intersect"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_13intersect, METH_O, __Pyx_DOCSTR(0)},
-  {__Pyx_NAMESTR("sample"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_15sample, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("viterbi_source_tree"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_7viterbi_source_tree, METH_NOARGS, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("viterbi_features"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_9viterbi_features, METH_NOARGS, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("kbest"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_11kbest, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("kbest_tree"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_14kbest_tree, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("sample"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_17sample, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("intersect"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_20intersect, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("prune"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_22prune, METH_VARARGS|METH_KEYWORDS, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("lattice"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_24lattice, METH_NOARGS, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("reweight"), (PyCFunction)__pyx_pw_5_cdec_10Hypergraph_26reweight, METH_O, __Pyx_DOCSTR(0)},
   {0, 0, 0, 0}
 };
 
@@ -3849,13 +6414,31 @@ static void __pyx_tp_dealloc_5_cdec_Lattice(PyObject *o) {
     PyObject *etype, *eval, *etb;
     PyErr_Fetch(&etype, &eval, &etb);
     ++Py_REFCNT(o);
-    __pyx_pw_5_cdec_7Lattice_7__dealloc__(o);
+    __pyx_pw_5_cdec_7Lattice_14__dealloc__(o);
     if (PyErr_Occurred()) PyErr_WriteUnraisable(o);
     --Py_REFCNT(o);
     PyErr_Restore(etype, eval, etb);
   }
   (*Py_TYPE(o)->tp_free)(o);
 }
+static PyObject *__pyx_sq_item_5_cdec_Lattice(PyObject *o, Py_ssize_t i) {
+  PyObject *r;
+  PyObject *x = PyInt_FromSsize_t(i); if(!x) return 0;
+  r = Py_TYPE(o)->tp_as_mapping->mp_subscript(o, x);
+  Py_DECREF(x);
+  return r;
+}
+
+static int __pyx_mp_ass_subscript_5_cdec_Lattice(PyObject *o, PyObject *i, PyObject *v) {
+  if (v) {
+    return __pyx_pw_5_cdec_7Lattice_5__setitem__(o, i, v);
+  }
+  else {
+    PyErr_Format(PyExc_NotImplementedError,
+      "Subscript deletion not supported by %s", Py_TYPE(o)->tp_name);
+    return -1;
+  }
+}
 
 static PyMethodDef __pyx_methods_5_cdec_Lattice[] = {
   {0, 0, 0, 0}
@@ -3920,10 +6503,10 @@ static PyNumberMethods __pyx_tp_as_number_Lattice = {
 };
 
 static PySequenceMethods __pyx_tp_as_sequence_Lattice = {
-  0, /*sq_length*/
+  __pyx_pw_5_cdec_7Lattice_7__len__, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
-  0, /*sq_item*/
+  __pyx_sq_item_5_cdec_Lattice, /*sq_item*/
   0, /*sq_slice*/
   0, /*sq_ass_item*/
   0, /*sq_ass_slice*/
@@ -3933,9 +6516,9 @@ static PySequenceMethods __pyx_tp_as_sequence_Lattice = {
 };
 
 static PyMappingMethods __pyx_tp_as_mapping_Lattice = {
-  0, /*mp_length*/
-  0, /*mp_subscript*/
-  0, /*mp_ass_subscript*/
+  __pyx_pw_5_cdec_7Lattice_7__len__, /*mp_length*/
+  __pyx_pw_5_cdec_7Lattice_3__getitem__, /*mp_subscript*/
+  __pyx_mp_ass_subscript_5_cdec_Lattice, /*mp_ass_subscript*/
 };
 
 static PyBufferProcs __pyx_tp_as_buffer_Lattice = {
@@ -3979,7 +6562,7 @@ static PyTypeObject __pyx_type_5_cdec_Lattice = {
   &__pyx_tp_as_mapping_Lattice, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
-  __pyx_pw_5_cdec_7Lattice_3__str__, /*tp_str*/
+  __pyx_pw_5_cdec_7Lattice_9__str__, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
   &__pyx_tp_as_buffer_Lattice, /*tp_as_buffer*/
@@ -3989,7 +6572,7 @@ static PyTypeObject __pyx_type_5_cdec_Lattice = {
   0, /*tp_clear*/
   0, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
-  __pyx_pw_5_cdec_7Lattice_5__iter__, /*tp_iter*/
+  __pyx_pw_5_cdec_7Lattice_11__iter__, /*tp_iter*/
   0, /*tp_iternext*/
   __pyx_methods_5_cdec_Lattice, /*tp_methods*/
   0, /*tp_members*/
@@ -4015,6 +6598,229 @@ static PyTypeObject __pyx_type_5_cdec_Lattice = {
   #endif
 };
 
+static PyObject *__pyx_tp_new_5_cdec_Decoder(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec_Decoder *p;
+  PyObject *o = (*t->tp_alloc)(t, 0);
+  if (!o) return 0;
+  p = ((struct __pyx_obj_5_cdec_Decoder *)o);
+  p->weights = ((struct __pyx_obj_5_cdec_DenseVector *)Py_None); Py_INCREF(Py_None);
+  if (__pyx_pw_5_cdec_7Decoder_1__cinit__(o, a, k) < 0) {
+    Py_DECREF(o); o = 0;
+  }
+  return o;
+}
+
+static void __pyx_tp_dealloc_5_cdec_Decoder(PyObject *o) {
+  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
+  {
+    PyObject *etype, *eval, *etb;
+    PyErr_Fetch(&etype, &eval, &etb);
+    ++Py_REFCNT(o);
+    __pyx_pw_5_cdec_7Decoder_3__dealloc__(o);
+    if (PyErr_Occurred()) PyErr_WriteUnraisable(o);
+    --Py_REFCNT(o);
+    PyErr_Restore(etype, eval, etb);
+  }
+  Py_XDECREF(((PyObject *)p->weights));
+  (*Py_TYPE(o)->tp_free)(o);
+}
+
+static int __pyx_tp_traverse_5_cdec_Decoder(PyObject *o, visitproc v, void *a) {
+  int e;
+  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
+  if (p->weights) {
+    e = (*v)(((PyObject*)p->weights), a); if (e) return e;
+  }
+  return 0;
+}
+
+static int __pyx_tp_clear_5_cdec_Decoder(PyObject *o) {
+  struct __pyx_obj_5_cdec_Decoder *p = (struct __pyx_obj_5_cdec_Decoder *)o;
+  PyObject* tmp;
+  tmp = ((PyObject*)p->weights);
+  p->weights = ((struct __pyx_obj_5_cdec_DenseVector *)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
+  return 0;
+}
+
+static PyObject *__pyx_getprop_5_cdec_7Decoder_weights(PyObject *o, void *x) {
+  return __pyx_pw_5_cdec_7Decoder_7weights_1__get__(o);
+}
+
+static int __pyx_setprop_5_cdec_7Decoder_weights(PyObject *o, PyObject *v, void *x) {
+  if (v) {
+    return __pyx_pw_5_cdec_7Decoder_7weights_3__set__(o, v);
+  }
+  else {
+    return __pyx_pw_5_cdec_7Decoder_7weights_5__del__(o);
+  }
+}
+
+static PyMethodDef __pyx_methods_5_cdec_Decoder[] = {
+  {__Pyx_NAMESTR("read_weights"), (PyCFunction)__pyx_pw_5_cdec_7Decoder_5read_weights, METH_O, __Pyx_DOCSTR(0)},
+  {__Pyx_NAMESTR("translate"), (PyCFunction)__pyx_pw_5_cdec_7Decoder_7translate, METH_VARARGS|METH_KEYWORDS, __Pyx_DOCSTR(0)},
+  {0, 0, 0, 0}
+};
+
+static struct PyGetSetDef __pyx_getsets_5_cdec_Decoder[] = {
+  {(char *)"weights", __pyx_getprop_5_cdec_7Decoder_weights, __pyx_setprop_5_cdec_7Decoder_weights, 0, 0},
+  {0, 0, 0, 0, 0}
+};
+
+static PyNumberMethods __pyx_tp_as_number_Decoder = {
+  0, /*nb_add*/
+  0, /*nb_subtract*/
+  0, /*nb_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_divide*/
+  #endif
+  0, /*nb_remainder*/
+  0, /*nb_divmod*/
+  0, /*nb_power*/
+  0, /*nb_negative*/
+  0, /*nb_positive*/
+  0, /*nb_absolute*/
+  0, /*nb_nonzero*/
+  0, /*nb_invert*/
+  0, /*nb_lshift*/
+  0, /*nb_rshift*/
+  0, /*nb_and*/
+  0, /*nb_xor*/
+  0, /*nb_or*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_coerce*/
+  #endif
+  0, /*nb_int*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_long*/
+  #else
+  0, /*reserved*/
+  #endif
+  0, /*nb_float*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_oct*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_hex*/
+  #endif
+  0, /*nb_inplace_add*/
+  0, /*nb_inplace_subtract*/
+  0, /*nb_inplace_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_inplace_divide*/
+  #endif
+  0, /*nb_inplace_remainder*/
+  0, /*nb_inplace_power*/
+  0, /*nb_inplace_lshift*/
+  0, /*nb_inplace_rshift*/
+  0, /*nb_inplace_and*/
+  0, /*nb_inplace_xor*/
+  0, /*nb_inplace_or*/
+  0, /*nb_floor_divide*/
+  0, /*nb_true_divide*/
+  0, /*nb_inplace_floor_divide*/
+  0, /*nb_inplace_true_divide*/
+  #if PY_VERSION_HEX >= 0x02050000
+  0, /*nb_index*/
+  #endif
+};
+
+static PySequenceMethods __pyx_tp_as_sequence_Decoder = {
+  0, /*sq_length*/
+  0, /*sq_concat*/
+  0, /*sq_repeat*/
+  0, /*sq_item*/
+  0, /*sq_slice*/
+  0, /*sq_ass_item*/
+  0, /*sq_ass_slice*/
+  0, /*sq_contains*/
+  0, /*sq_inplace_concat*/
+  0, /*sq_inplace_repeat*/
+};
+
+static PyMappingMethods __pyx_tp_as_mapping_Decoder = {
+  0, /*mp_length*/
+  0, /*mp_subscript*/
+  0, /*mp_ass_subscript*/
+};
+
+static PyBufferProcs __pyx_tp_as_buffer_Decoder = {
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getreadbuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getwritebuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getsegcount*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getcharbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_getbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_releasebuffer*/
+  #endif
+};
+
+static PyTypeObject __pyx_type_5_cdec_Decoder = {
+  PyVarObject_HEAD_INIT(0, 0)
+  __Pyx_NAMESTR("_cdec.Decoder"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec_Decoder), /*tp_basicsize*/
+  0, /*tp_itemsize*/
+  __pyx_tp_dealloc_5_cdec_Decoder, /*tp_dealloc*/
+  0, /*tp_print*/
+  0, /*tp_getattr*/
+  0, /*tp_setattr*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*tp_compare*/
+  #else
+  0, /*reserved*/
+  #endif
+  0, /*tp_repr*/
+  &__pyx_tp_as_number_Decoder, /*tp_as_number*/
+  &__pyx_tp_as_sequence_Decoder, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping_Decoder, /*tp_as_mapping*/
+  0, /*tp_hash*/
+  0, /*tp_call*/
+  0, /*tp_str*/
+  0, /*tp_getattro*/
+  0, /*tp_setattro*/
+  &__pyx_tp_as_buffer_Decoder, /*tp_as_buffer*/
+  Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_BASETYPE|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+  0, /*tp_doc*/
+  __pyx_tp_traverse_5_cdec_Decoder, /*tp_traverse*/
+  __pyx_tp_clear_5_cdec_Decoder, /*tp_clear*/
+  0, /*tp_richcompare*/
+  0, /*tp_weaklistoffset*/
+  0, /*tp_iter*/
+  0, /*tp_iternext*/
+  __pyx_methods_5_cdec_Decoder, /*tp_methods*/
+  0, /*tp_members*/
+  __pyx_getsets_5_cdec_Decoder, /*tp_getset*/
+  0, /*tp_base*/
+  0, /*tp_dict*/
+  0, /*tp_descr_get*/
+  0, /*tp_descr_set*/
+  0, /*tp_dictoffset*/
+  0, /*tp_init*/
+  0, /*tp_alloc*/
+  __pyx_tp_new_5_cdec_Decoder, /*tp_new*/
+  0, /*tp_free*/
+  0, /*tp_is_gc*/
+  0, /*tp_bases*/
+  0, /*tp_mro*/
+  0, /*tp_cache*/
+  0, /*tp_subclasses*/
+  0, /*tp_weaklist*/
+  0, /*tp_del*/
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*tp_version_tag*/
+  #endif
+};
+
 static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct____iter__(PyTypeObject *t, PyObject *a, PyObject *k) {
   struct __pyx_obj_5_cdec___pyx_scope_struct____iter__ *p;
   PyObject *o = (*t->tp_alloc)(t, 0);
@@ -4043,7 +6849,7 @@ static int __pyx_tp_clear_5_cdec___pyx_scope_struct____iter__(PyObject *o) {
   struct __pyx_obj_5_cdec___pyx_scope_struct____iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct____iter__ *)o;
   PyObject* tmp;
   tmp = ((PyObject*)p->__pyx_v_self);
-  p->__pyx_v_self = ((struct __pyx_obj_5_cdec_Weights *)Py_None); Py_INCREF(Py_None);
+  p->__pyx_v_self = ((struct __pyx_obj_5_cdec_DenseVector *)Py_None); Py_INCREF(Py_None);
   Py_XDECREF(tmp);
   return 0;
 }
@@ -4206,60 +7012,259 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct____iter__ = {
   #endif
 };
 
-static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_1_kbest(PyTypeObject *t, PyObject *a, PyObject *k) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *p;
+static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_1___iter__(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *p;
   PyObject *o = (*t->tp_alloc)(t, 0);
   if (!o) return 0;
-  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *)o);
+  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *)o);
+  p->__pyx_v_fname = 0;
   p->__pyx_v_self = 0;
+  return o;
+}
+
+static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_1___iter__(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *)o;
+  Py_XDECREF(((PyObject *)p->__pyx_v_fname));
+  Py_XDECREF(((PyObject *)p->__pyx_v_self));
+  (*Py_TYPE(o)->tp_free)(o);
+}
+
+static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_1___iter__(PyObject *o, visitproc v, void *a) {
+  int e;
+  struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *)o;
+  if (p->__pyx_v_fname) {
+    e = (*v)(p->__pyx_v_fname, a); if (e) return e;
+  }
+  if (p->__pyx_v_self) {
+    e = (*v)(((PyObject*)p->__pyx_v_self), a); if (e) return e;
+  }
+  return 0;
+}
+
+static int __pyx_tp_clear_5_cdec___pyx_scope_struct_1___iter__(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__ *)o;
+  PyObject* tmp;
+  tmp = ((PyObject*)p->__pyx_v_fname);
+  p->__pyx_v_fname = ((PyObject*)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
+  tmp = ((PyObject*)p->__pyx_v_self);
+  p->__pyx_v_self = ((struct __pyx_obj_5_cdec_SparseVector *)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
+  return 0;
+}
+
+static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_1___iter__[] = {
+  {0, 0, 0, 0}
+};
+
+static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_1___iter__ = {
+  0, /*nb_add*/
+  0, /*nb_subtract*/
+  0, /*nb_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_divide*/
+  #endif
+  0, /*nb_remainder*/
+  0, /*nb_divmod*/
+  0, /*nb_power*/
+  0, /*nb_negative*/
+  0, /*nb_positive*/
+  0, /*nb_absolute*/
+  0, /*nb_nonzero*/
+  0, /*nb_invert*/
+  0, /*nb_lshift*/
+  0, /*nb_rshift*/
+  0, /*nb_and*/
+  0, /*nb_xor*/
+  0, /*nb_or*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_coerce*/
+  #endif
+  0, /*nb_int*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_long*/
+  #else
+  0, /*reserved*/
+  #endif
+  0, /*nb_float*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_oct*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_hex*/
+  #endif
+  0, /*nb_inplace_add*/
+  0, /*nb_inplace_subtract*/
+  0, /*nb_inplace_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_inplace_divide*/
+  #endif
+  0, /*nb_inplace_remainder*/
+  0, /*nb_inplace_power*/
+  0, /*nb_inplace_lshift*/
+  0, /*nb_inplace_rshift*/
+  0, /*nb_inplace_and*/
+  0, /*nb_inplace_xor*/
+  0, /*nb_inplace_or*/
+  0, /*nb_floor_divide*/
+  0, /*nb_true_divide*/
+  0, /*nb_inplace_floor_divide*/
+  0, /*nb_inplace_true_divide*/
+  #if PY_VERSION_HEX >= 0x02050000
+  0, /*nb_index*/
+  #endif
+};
+
+static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_1___iter__ = {
+  0, /*sq_length*/
+  0, /*sq_concat*/
+  0, /*sq_repeat*/
+  0, /*sq_item*/
+  0, /*sq_slice*/
+  0, /*sq_ass_item*/
+  0, /*sq_ass_slice*/
+  0, /*sq_contains*/
+  0, /*sq_inplace_concat*/
+  0, /*sq_inplace_repeat*/
+};
+
+static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_1___iter__ = {
+  0, /*mp_length*/
+  0, /*mp_subscript*/
+  0, /*mp_ass_subscript*/
+};
+
+static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_1___iter__ = {
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getreadbuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getwritebuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getsegcount*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getcharbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_getbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_releasebuffer*/
+  #endif
+};
+
+static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_1___iter__ = {
+  PyVarObject_HEAD_INIT(0, 0)
+  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_1___iter__"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_1___iter__), /*tp_basicsize*/
+  0, /*tp_itemsize*/
+  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_1___iter__, /*tp_dealloc*/
+  0, /*tp_print*/
+  0, /*tp_getattr*/
+  0, /*tp_setattr*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*tp_compare*/
+  #else
+  0, /*reserved*/
+  #endif
+  0, /*tp_repr*/
+  &__pyx_tp_as_number___pyx_scope_struct_1___iter__, /*tp_as_number*/
+  &__pyx_tp_as_sequence___pyx_scope_struct_1___iter__, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping___pyx_scope_struct_1___iter__, /*tp_as_mapping*/
+  0, /*tp_hash*/
+  0, /*tp_call*/
+  0, /*tp_str*/
+  0, /*tp_getattro*/
+  0, /*tp_setattro*/
+  &__pyx_tp_as_buffer___pyx_scope_struct_1___iter__, /*tp_as_buffer*/
+  Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+  0, /*tp_doc*/
+  __pyx_tp_traverse_5_cdec___pyx_scope_struct_1___iter__, /*tp_traverse*/
+  __pyx_tp_clear_5_cdec___pyx_scope_struct_1___iter__, /*tp_clear*/
+  0, /*tp_richcompare*/
+  0, /*tp_weaklistoffset*/
+  0, /*tp_iter*/
+  0, /*tp_iternext*/
+  __pyx_methods_5_cdec___pyx_scope_struct_1___iter__, /*tp_methods*/
+  0, /*tp_members*/
+  0, /*tp_getset*/
+  0, /*tp_base*/
+  0, /*tp_dict*/
+  0, /*tp_descr_get*/
+  0, /*tp_descr_set*/
+  0, /*tp_dictoffset*/
+  0, /*tp_init*/
+  0, /*tp_alloc*/
+  __pyx_tp_new_5_cdec___pyx_scope_struct_1___iter__, /*tp_new*/
+  0, /*tp_free*/
+  0, /*tp_is_gc*/
+  0, /*tp_bases*/
+  0, /*tp_mro*/
+  0, /*tp_cache*/
+  0, /*tp_subclasses*/
+  0, /*tp_weaklist*/
+  0, /*tp_del*/
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*tp_version_tag*/
+  #endif
+};
+
+static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_2_kbest(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *p;
+  PyObject *o = (*t->tp_alloc)(t, 0);
+  if (!o) return 0;
+  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)o);
+  p->__pyx_v_self = 0;
+  p->__pyx_v_sentence = 0;
   p->__pyx_v_size = 0;
-  p->__pyx_v_tree = 0;
   return o;
 }
 
-static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_1_kbest(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *)o;
+static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_2_kbest(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)o;
   Py_XDECREF(((PyObject *)p->__pyx_v_self));
+  Py_XDECREF(((PyObject *)p->__pyx_v_sentence));
   Py_XDECREF(p->__pyx_v_size);
-  Py_XDECREF(((PyObject *)p->__pyx_v_tree));
   (*Py_TYPE(o)->tp_free)(o);
 }
 
-static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_1_kbest(PyObject *o, visitproc v, void *a) {
+static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_2_kbest(PyObject *o, visitproc v, void *a) {
   int e;
-  struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *)o;
+  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)o;
   if (p->__pyx_v_self) {
     e = (*v)(((PyObject*)p->__pyx_v_self), a); if (e) return e;
   }
+  if (p->__pyx_v_sentence) {
+    e = (*v)(p->__pyx_v_sentence, a); if (e) return e;
+  }
   if (p->__pyx_v_size) {
     e = (*v)(p->__pyx_v_size, a); if (e) return e;
   }
-  if (p->__pyx_v_tree) {
-    e = (*v)(p->__pyx_v_tree, a); if (e) return e;
-  }
   return 0;
 }
 
-static int __pyx_tp_clear_5_cdec___pyx_scope_struct_1_kbest(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest *)o;
+static int __pyx_tp_clear_5_cdec___pyx_scope_struct_2_kbest(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest *)o;
   PyObject* tmp;
   tmp = ((PyObject*)p->__pyx_v_self);
   p->__pyx_v_self = ((struct __pyx_obj_5_cdec_Hypergraph *)Py_None); Py_INCREF(Py_None);
   Py_XDECREF(tmp);
+  tmp = ((PyObject*)p->__pyx_v_sentence);
+  p->__pyx_v_sentence = ((PyObject*)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
   tmp = ((PyObject*)p->__pyx_v_size);
   p->__pyx_v_size = Py_None; Py_INCREF(Py_None);
   Py_XDECREF(tmp);
-  tmp = ((PyObject*)p->__pyx_v_tree);
-  p->__pyx_v_tree = ((PyObject*)Py_None); Py_INCREF(Py_None);
-  Py_XDECREF(tmp);
   return 0;
 }
 
-static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_1_kbest[] = {
+static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_2_kbest[] = {
   {0, 0, 0, 0}
 };
 
-static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_1_kbest = {
+static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_2_kbest = {
   0, /*nb_add*/
   0, /*nb_subtract*/
   0, /*nb_multiply*/
@@ -4317,7 +7322,7 @@ static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_1_kbest = {
   #endif
 };
 
-static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_1_kbest = {
+static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_2_kbest = {
   0, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
@@ -4330,13 +7335,13 @@ static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_1_kbest = {
   0, /*sq_inplace_repeat*/
 };
 
-static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_1_kbest = {
+static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_2_kbest = {
   0, /*mp_length*/
   0, /*mp_subscript*/
   0, /*mp_ass_subscript*/
 };
 
-static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_1_kbest = {
+static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_2_kbest = {
   #if PY_MAJOR_VERSION < 3
   0, /*bf_getreadbuffer*/
   #endif
@@ -4357,12 +7362,12 @@ static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_1_kbest = {
   #endif
 };
 
-static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_1_kbest = {
+static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_2_kbest = {
   PyVarObject_HEAD_INIT(0, 0)
-  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_1_kbest"), /*tp_name*/
-  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_1_kbest), /*tp_basicsize*/
+  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_2_kbest"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest), /*tp_basicsize*/
   0, /*tp_itemsize*/
-  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_1_kbest, /*tp_dealloc*/
+  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_2_kbest, /*tp_dealloc*/
   0, /*tp_print*/
   0, /*tp_getattr*/
   0, /*tp_setattr*/
@@ -4372,24 +7377,24 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_1_kbest = {
   0, /*reserved*/
   #endif
   0, /*tp_repr*/
-  &__pyx_tp_as_number___pyx_scope_struct_1_kbest, /*tp_as_number*/
-  &__pyx_tp_as_sequence___pyx_scope_struct_1_kbest, /*tp_as_sequence*/
-  &__pyx_tp_as_mapping___pyx_scope_struct_1_kbest, /*tp_as_mapping*/
+  &__pyx_tp_as_number___pyx_scope_struct_2_kbest, /*tp_as_number*/
+  &__pyx_tp_as_sequence___pyx_scope_struct_2_kbest, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping___pyx_scope_struct_2_kbest, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
   0, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
-  &__pyx_tp_as_buffer___pyx_scope_struct_1_kbest, /*tp_as_buffer*/
+  &__pyx_tp_as_buffer___pyx_scope_struct_2_kbest, /*tp_as_buffer*/
   Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
   0, /*tp_doc*/
-  __pyx_tp_traverse_5_cdec___pyx_scope_struct_1_kbest, /*tp_traverse*/
-  __pyx_tp_clear_5_cdec___pyx_scope_struct_1_kbest, /*tp_clear*/
+  __pyx_tp_traverse_5_cdec___pyx_scope_struct_2_kbest, /*tp_traverse*/
+  __pyx_tp_clear_5_cdec___pyx_scope_struct_2_kbest, /*tp_clear*/
   0, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
   0, /*tp_iter*/
   0, /*tp_iternext*/
-  __pyx_methods_5_cdec___pyx_scope_struct_1_kbest, /*tp_methods*/
+  __pyx_methods_5_cdec___pyx_scope_struct_2_kbest, /*tp_methods*/
   0, /*tp_members*/
   0, /*tp_getset*/
   0, /*tp_base*/
@@ -4399,7 +7404,7 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_1_kbest = {
   0, /*tp_dictoffset*/
   0, /*tp_init*/
   0, /*tp_alloc*/
-  __pyx_tp_new_5_cdec___pyx_scope_struct_1_kbest, /*tp_new*/
+  __pyx_tp_new_5_cdec___pyx_scope_struct_2_kbest, /*tp_new*/
   0, /*tp_free*/
   0, /*tp_is_gc*/
   0, /*tp_bases*/
@@ -4413,60 +7418,60 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_1_kbest = {
   #endif
 };
 
-static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_2_kbest_tree(PyTypeObject *t, PyObject *a, PyObject *k) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *p;
+static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_3_kbest_tree(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *p;
   PyObject *o = (*t->tp_alloc)(t, 0);
   if (!o) return 0;
-  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *)o);
+  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)o);
   p->__pyx_v_self = 0;
-  p->__pyx_v_sentence = 0;
   p->__pyx_v_size = 0;
+  p->__pyx_v_tree = 0;
   return o;
 }
 
-static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_2_kbest_tree(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *)o;
+static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_3_kbest_tree(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)o;
   Py_XDECREF(((PyObject *)p->__pyx_v_self));
-  Py_XDECREF(((PyObject *)p->__pyx_v_sentence));
   Py_XDECREF(p->__pyx_v_size);
+  Py_XDECREF(((PyObject *)p->__pyx_v_tree));
   (*Py_TYPE(o)->tp_free)(o);
 }
 
-static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_2_kbest_tree(PyObject *o, visitproc v, void *a) {
+static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_3_kbest_tree(PyObject *o, visitproc v, void *a) {
   int e;
-  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *)o;
+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)o;
   if (p->__pyx_v_self) {
     e = (*v)(((PyObject*)p->__pyx_v_self), a); if (e) return e;
   }
-  if (p->__pyx_v_sentence) {
-    e = (*v)(p->__pyx_v_sentence, a); if (e) return e;
-  }
   if (p->__pyx_v_size) {
     e = (*v)(p->__pyx_v_size, a); if (e) return e;
   }
+  if (p->__pyx_v_tree) {
+    e = (*v)(p->__pyx_v_tree, a); if (e) return e;
+  }
   return 0;
 }
 
-static int __pyx_tp_clear_5_cdec___pyx_scope_struct_2_kbest_tree(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree *)o;
+static int __pyx_tp_clear_5_cdec___pyx_scope_struct_3_kbest_tree(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree *)o;
   PyObject* tmp;
   tmp = ((PyObject*)p->__pyx_v_self);
   p->__pyx_v_self = ((struct __pyx_obj_5_cdec_Hypergraph *)Py_None); Py_INCREF(Py_None);
   Py_XDECREF(tmp);
-  tmp = ((PyObject*)p->__pyx_v_sentence);
-  p->__pyx_v_sentence = ((PyObject*)Py_None); Py_INCREF(Py_None);
-  Py_XDECREF(tmp);
   tmp = ((PyObject*)p->__pyx_v_size);
   p->__pyx_v_size = Py_None; Py_INCREF(Py_None);
   Py_XDECREF(tmp);
+  tmp = ((PyObject*)p->__pyx_v_tree);
+  p->__pyx_v_tree = ((PyObject*)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
   return 0;
 }
 
-static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_2_kbest_tree[] = {
+static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_3_kbest_tree[] = {
   {0, 0, 0, 0}
 };
 
-static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_2_kbest_tree = {
+static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_3_kbest_tree = {
   0, /*nb_add*/
   0, /*nb_subtract*/
   0, /*nb_multiply*/
@@ -4524,7 +7529,7 @@ static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_2_kbest_tree = {
   #endif
 };
 
-static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_2_kbest_tree = {
+static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_3_kbest_tree = {
   0, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
@@ -4537,13 +7542,13 @@ static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_2_kbest_tree =
   0, /*sq_inplace_repeat*/
 };
 
-static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_2_kbest_tree = {
+static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_3_kbest_tree = {
   0, /*mp_length*/
   0, /*mp_subscript*/
   0, /*mp_ass_subscript*/
 };
 
-static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_2_kbest_tree = {
+static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_3_kbest_tree = {
   #if PY_MAJOR_VERSION < 3
   0, /*bf_getreadbuffer*/
   #endif
@@ -4564,12 +7569,12 @@ static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_2_kbest_tree = {
   #endif
 };
 
-static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree = {
+static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_3_kbest_tree = {
   PyVarObject_HEAD_INIT(0, 0)
-  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_2_kbest_tree"), /*tp_name*/
-  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_2_kbest_tree), /*tp_basicsize*/
+  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_3_kbest_tree"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_3_kbest_tree), /*tp_basicsize*/
   0, /*tp_itemsize*/
-  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_2_kbest_tree, /*tp_dealloc*/
+  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_3_kbest_tree, /*tp_dealloc*/
   0, /*tp_print*/
   0, /*tp_getattr*/
   0, /*tp_setattr*/
@@ -4579,24 +7584,24 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree = {
   0, /*reserved*/
   #endif
   0, /*tp_repr*/
-  &__pyx_tp_as_number___pyx_scope_struct_2_kbest_tree, /*tp_as_number*/
-  &__pyx_tp_as_sequence___pyx_scope_struct_2_kbest_tree, /*tp_as_sequence*/
-  &__pyx_tp_as_mapping___pyx_scope_struct_2_kbest_tree, /*tp_as_mapping*/
+  &__pyx_tp_as_number___pyx_scope_struct_3_kbest_tree, /*tp_as_number*/
+  &__pyx_tp_as_sequence___pyx_scope_struct_3_kbest_tree, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping___pyx_scope_struct_3_kbest_tree, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
   0, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
-  &__pyx_tp_as_buffer___pyx_scope_struct_2_kbest_tree, /*tp_as_buffer*/
+  &__pyx_tp_as_buffer___pyx_scope_struct_3_kbest_tree, /*tp_as_buffer*/
   Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
   0, /*tp_doc*/
-  __pyx_tp_traverse_5_cdec___pyx_scope_struct_2_kbest_tree, /*tp_traverse*/
-  __pyx_tp_clear_5_cdec___pyx_scope_struct_2_kbest_tree, /*tp_clear*/
+  __pyx_tp_traverse_5_cdec___pyx_scope_struct_3_kbest_tree, /*tp_traverse*/
+  __pyx_tp_clear_5_cdec___pyx_scope_struct_3_kbest_tree, /*tp_clear*/
   0, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
   0, /*tp_iter*/
   0, /*tp_iternext*/
-  __pyx_methods_5_cdec___pyx_scope_struct_2_kbest_tree, /*tp_methods*/
+  __pyx_methods_5_cdec___pyx_scope_struct_3_kbest_tree, /*tp_methods*/
   0, /*tp_members*/
   0, /*tp_getset*/
   0, /*tp_base*/
@@ -4606,7 +7611,7 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree = {
   0, /*tp_dictoffset*/
   0, /*tp_init*/
   0, /*tp_alloc*/
-  __pyx_tp_new_5_cdec___pyx_scope_struct_2_kbest_tree, /*tp_new*/
+  __pyx_tp_new_5_cdec___pyx_scope_struct_3_kbest_tree, /*tp_new*/
   0, /*tp_free*/
   0, /*tp_is_gc*/
   0, /*tp_bases*/
@@ -4620,26 +7625,26 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree = {
   #endif
 };
 
-static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_3_sample(PyTypeObject *t, PyObject *a, PyObject *k) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *p;
+static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_4_sample(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *p;
   PyObject *o = (*t->tp_alloc)(t, 0);
   if (!o) return 0;
-  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *)o);
+  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)o);
   p->__pyx_v_self = 0;
   p->__pyx_v_sentence = 0;
   return o;
 }
 
-static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_3_sample(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *)o;
+static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_4_sample(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)o;
   Py_XDECREF(((PyObject *)p->__pyx_v_self));
   Py_XDECREF(((PyObject *)p->__pyx_v_sentence));
   (*Py_TYPE(o)->tp_free)(o);
 }
 
-static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_3_sample(PyObject *o, visitproc v, void *a) {
+static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_4_sample(PyObject *o, visitproc v, void *a) {
   int e;
-  struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *)o;
+  struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)o;
   if (p->__pyx_v_self) {
     e = (*v)(((PyObject*)p->__pyx_v_self), a); if (e) return e;
   }
@@ -4649,8 +7654,8 @@ static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_3_sample(PyObject *o, vis
   return 0;
 }
 
-static int __pyx_tp_clear_5_cdec___pyx_scope_struct_3_sample(PyObject *o) {
-  struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample *)o;
+static int __pyx_tp_clear_5_cdec___pyx_scope_struct_4_sample(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample *)o;
   PyObject* tmp;
   tmp = ((PyObject*)p->__pyx_v_self);
   p->__pyx_v_self = ((struct __pyx_obj_5_cdec_Hypergraph *)Py_None); Py_INCREF(Py_None);
@@ -4661,11 +7666,11 @@ static int __pyx_tp_clear_5_cdec___pyx_scope_struct_3_sample(PyObject *o) {
   return 0;
 }
 
-static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_3_sample[] = {
+static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_4_sample[] = {
   {0, 0, 0, 0}
 };
 
-static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_3_sample = {
+static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_4_sample = {
   0, /*nb_add*/
   0, /*nb_subtract*/
   0, /*nb_multiply*/
@@ -4723,7 +7728,7 @@ static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_3_sample = {
   #endif
 };
 
-static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_3_sample = {
+static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_4_sample = {
   0, /*sq_length*/
   0, /*sq_concat*/
   0, /*sq_repeat*/
@@ -4736,13 +7741,13 @@ static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_3_sample = {
   0, /*sq_inplace_repeat*/
 };
 
-static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_3_sample = {
+static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_4_sample = {
   0, /*mp_length*/
   0, /*mp_subscript*/
   0, /*mp_ass_subscript*/
 };
 
-static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_3_sample = {
+static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_4_sample = {
   #if PY_MAJOR_VERSION < 3
   0, /*bf_getreadbuffer*/
   #endif
@@ -4763,12 +7768,12 @@ static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_3_sample = {
   #endif
 };
 
-static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_3_sample = {
+static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_4_sample = {
   PyVarObject_HEAD_INIT(0, 0)
-  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_3_sample"), /*tp_name*/
-  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_3_sample), /*tp_basicsize*/
+  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_4_sample"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_4_sample), /*tp_basicsize*/
   0, /*tp_itemsize*/
-  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_3_sample, /*tp_dealloc*/
+  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_4_sample, /*tp_dealloc*/
   0, /*tp_print*/
   0, /*tp_getattr*/
   0, /*tp_setattr*/
@@ -4778,24 +7783,24 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_3_sample = {
   0, /*reserved*/
   #endif
   0, /*tp_repr*/
-  &__pyx_tp_as_number___pyx_scope_struct_3_sample, /*tp_as_number*/
-  &__pyx_tp_as_sequence___pyx_scope_struct_3_sample, /*tp_as_sequence*/
-  &__pyx_tp_as_mapping___pyx_scope_struct_3_sample, /*tp_as_mapping*/
+  &__pyx_tp_as_number___pyx_scope_struct_4_sample, /*tp_as_number*/
+  &__pyx_tp_as_sequence___pyx_scope_struct_4_sample, /*tp_as_sequence*/
+  &__pyx_tp_as_mapping___pyx_scope_struct_4_sample, /*tp_as_mapping*/
   0, /*tp_hash*/
   0, /*tp_call*/
   0, /*tp_str*/
   0, /*tp_getattro*/
   0, /*tp_setattro*/
-  &__pyx_tp_as_buffer___pyx_scope_struct_3_sample, /*tp_as_buffer*/
+  &__pyx_tp_as_buffer___pyx_scope_struct_4_sample, /*tp_as_buffer*/
   Py_TPFLAGS_DEFAULT|Py_TPFLAGS_CHECKTYPES|Py_TPFLAGS_HAVE_NEWBUFFER|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
   0, /*tp_doc*/
-  __pyx_tp_traverse_5_cdec___pyx_scope_struct_3_sample, /*tp_traverse*/
-  __pyx_tp_clear_5_cdec___pyx_scope_struct_3_sample, /*tp_clear*/
+  __pyx_tp_traverse_5_cdec___pyx_scope_struct_4_sample, /*tp_traverse*/
+  __pyx_tp_clear_5_cdec___pyx_scope_struct_4_sample, /*tp_clear*/
   0, /*tp_richcompare*/
   0, /*tp_weaklistoffset*/
   0, /*tp_iter*/
   0, /*tp_iternext*/
-  __pyx_methods_5_cdec___pyx_scope_struct_3_sample, /*tp_methods*/
+  __pyx_methods_5_cdec___pyx_scope_struct_4_sample, /*tp_methods*/
   0, /*tp_members*/
   0, /*tp_getset*/
   0, /*tp_base*/
@@ -4805,7 +7810,198 @@ static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_3_sample = {
   0, /*tp_dictoffset*/
   0, /*tp_init*/
   0, /*tp_alloc*/
-  __pyx_tp_new_5_cdec___pyx_scope_struct_3_sample, /*tp_new*/
+  __pyx_tp_new_5_cdec___pyx_scope_struct_4_sample, /*tp_new*/
+  0, /*tp_free*/
+  0, /*tp_is_gc*/
+  0, /*tp_bases*/
+  0, /*tp_mro*/
+  0, /*tp_cache*/
+  0, /*tp_subclasses*/
+  0, /*tp_weaklist*/
+  0, /*tp_del*/
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*tp_version_tag*/
+  #endif
+};
+
+static PyObject *__pyx_tp_new_5_cdec___pyx_scope_struct_5___iter__(PyTypeObject *t, PyObject *a, PyObject *k) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *p;
+  PyObject *o = (*t->tp_alloc)(t, 0);
+  if (!o) return 0;
+  p = ((struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *)o);
+  p->__pyx_v_self = 0;
+  return o;
+}
+
+static void __pyx_tp_dealloc_5_cdec___pyx_scope_struct_5___iter__(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *)o;
+  Py_XDECREF(((PyObject *)p->__pyx_v_self));
+  (*Py_TYPE(o)->tp_free)(o);
+}
+
+static int __pyx_tp_traverse_5_cdec___pyx_scope_struct_5___iter__(PyObject *o, visitproc v, void *a) {
+  int e;
+  struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *)o;
+  if (p->__pyx_v_self) {
+    e = (*v)(((PyObject*)p->__pyx_v_self), a); if (e) return e;
+  }
+  return 0;
+}
+
+static int __pyx_tp_clear_5_cdec___pyx_scope_struct_5___iter__(PyObject *o) {
+  struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *p = (struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__ *)o;
+  PyObject* tmp;
+  tmp = ((PyObject*)p->__pyx_v_self);
+  p->__pyx_v_self = ((struct __pyx_obj_5_cdec_Lattice *)Py_None); Py_INCREF(Py_None);
+  Py_XDECREF(tmp);
+  return 0;
+}
+
+static PyMethodDef __pyx_methods_5_cdec___pyx_scope_struct_5___iter__[] = {
+  {0, 0, 0, 0}
+};
+
+static PyNumberMethods __pyx_tp_as_number___pyx_scope_struct_5___iter__ = {
+  0, /*nb_add*/
+  0, /*nb_subtract*/
+  0, /*nb_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_divide*/
+  #endif
+  0, /*nb_remainder*/
+  0, /*nb_divmod*/
+  0, /*nb_power*/
+  0, /*nb_negative*/
+  0, /*nb_positive*/
+  0, /*nb_absolute*/
+  0, /*nb_nonzero*/
+  0, /*nb_invert*/
+  0, /*nb_lshift*/
+  0, /*nb_rshift*/
+  0, /*nb_and*/
+  0, /*nb_xor*/
+  0, /*nb_or*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_coerce*/
+  #endif
+  0, /*nb_int*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_long*/
+  #else
+  0, /*reserved*/
+  #endif
+  0, /*nb_float*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_oct*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_hex*/
+  #endif
+  0, /*nb_inplace_add*/
+  0, /*nb_inplace_subtract*/
+  0, /*nb_inplace_multiply*/
+  #if PY_MAJOR_VERSION < 3
+  0, /*nb_inplace_divide*/
+  #endif
+  0, /*nb_inplace_remainder*/
+  0, /*nb_inplace_power*/
+  0, /*nb_inplace_lshift*/
+  0, /*nb_inplace_rshift*/
+  0, /*nb_inplace_and*/
+  0, /*nb_inplace_xor*/
+  0, /*nb_inplace_or*/
+  0, /*nb_floor_divide*/
+  0, /*nb_true_divide*/
+  0, /*nb_inplace_floor_divide*/
+  0, /*nb_inplace_true_divide*/
+  #if PY_VERSION_HEX >= 0x02050000
+  0, /*nb_index*/
+  #endif
+};
+
+static PySequenceMethods __pyx_tp_as_sequence___pyx_scope_struct_5___iter__ = {
+  0, /*sq_length*/
+  0, /*sq_concat*/
+  0, /*sq_repeat*/
+  0, /*sq_item*/
+  0, /*sq_slice*/
+  0, /*sq_ass_item*/
+  0, /*sq_ass_slice*/
+  0, /*sq_contains*/
+  0, /*sq_inplace_concat*/
+  0, /*sq_inplace_repeat*/
+};
+
+static PyMappingMethods __pyx_tp_as_mapping___pyx_scope_struct_5___iter__ = {
+  0, /*mp_length*/
+  0, /*mp_subscript*/
+  0, /*mp_ass_subscript*/
+};
+
+static PyBufferProcs __pyx_tp_as_buffer___pyx_scope_struct_5___iter__ = {
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getreadbuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getwritebuffer*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getsegcount*/
+  #endif
+  #if PY_MAJOR_VERSION < 3
+  0, /*bf_getcharbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_getbuffer*/
+  #endif
+  #if PY_VERSION_HEX >= 0x02060000
+  0, /*bf_releasebuffer*/
+  #endif
+};
+
+static PyTypeObject __pyx_type_5_cdec___pyx_scope_struct_5___iter__ = {
+  PyVarObject_HEAD_INIT(0, 0)
+  __Pyx_NAMESTR("_cdec.__pyx_scope_struct_5___iter__"), /*tp_name*/
+  sizeof(struct __pyx_obj_5_cdec___pyx_scope_struct_5___iter__), /*tp_basicsize*/
+  0, /*tp_itemsize*/
+  __pyx_tp_dealloc_5_cdec___pyx_scope_struct_5___iter__, /*tp_dealloc*/
+  0, /*tp_print*/
+  0, /*tp_getattr*/
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+ *         cdef vector[lattice.LatticeArc] arc_vector = self.lattice[0][index]
+ */
+  __pyx_k_tuple_15 = PyTuple_New(1); if (unlikely(!__pyx_k_tuple_15)) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 21; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_15);
+  __Pyx_INCREF(((PyObject *)__pyx_kp_s_14));
+  PyTuple_SET_ITEM(__pyx_k_tuple_15, 0, ((PyObject *)__pyx_kp_s_14));
+  __Pyx_GIVEREF(((PyObject *)__pyx_kp_s_14));
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_15));
+
+  /* "/Users/vchahun/Sandbox/cdec/python/src/lattice.pxi":30
+ *             arc = &arc_vector[i]
+ *             label = TDConvert(arc.label)
+ *             arcs.append((label.decode('utf8'), arc.cost, arc.dist2next))             # <<<<<<<<<<<<<<
+ *         return tuple(arcs)
+ * 
+ */
+  __pyx_k_tuple_16 = PyTuple_New(1); if (unlikely(!__pyx_k_tuple_16)) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 30; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_16);
+  __Pyx_INCREF(((PyObject *)__pyx_n_s__utf8));
+  PyTuple_SET_ITEM(__pyx_k_tuple_16, 0, ((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_16));
+
+  /* "/Users/vchahun/Sandbox/cdec/python/src/lattice.pxi":35
+ *     def __setitem__(self, int index, tuple arcs):
+ *         if not 0 <= index < len(self):
+ *             raise IndexError('lattice index out of range')             # <<<<<<<<<<<<<<
+ *         cdef lattice.LatticeArc* arc
+ *         for (label, cost, dist2next) in arcs:
+ */
+  __pyx_k_tuple_17 = PyTuple_New(1); if (unlikely(!__pyx_k_tuple_17)) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 35; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_17);
+  __Pyx_INCREF(((PyObject *)__pyx_kp_s_14));
+  PyTuple_SET_ITEM(__pyx_k_tuple_17, 0, ((PyObject *)__pyx_kp_s_14));
+  __Pyx_GIVEREF(((PyObject *)__pyx_kp_s_14));
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_17));
+
+  /* "/Users/vchahun/Sandbox/cdec/python/src/lattice.pxi":39
+ *         for (label, cost, dist2next) in arcs:
+ *             if isinstance(label, unicode):
+ *                 label = label.encode('utf8')             # <<<<<<<<<<<<<<
+ *             arc = new lattice.LatticeArc(TDConvert(<char *>label), cost, dist2next)
+ *             self.lattice[0][index].push_back(arc[0])
+ */
+  __pyx_k_tuple_18 = PyTuple_New(1); if (unlikely(!__pyx_k_tuple_18)) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 39; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_18);
+  __Pyx_INCREF(((PyObject *)__pyx_n_s__utf8));
+  PyTuple_SET_ITEM(__pyx_k_tuple_18, 0, ((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_18));
+
+  /* "_cdec.pyx":31
+ * 
+ *     def read_weights(self, cfg):
+ *         with open(cfg) as fp:             # <<<<<<<<<<<<<<
+ *             for line in fp:
+ *                 fname, value = line.split()
+ */
+  __pyx_k_tuple_19 = PyTuple_New(3); if (unlikely(!__pyx_k_tuple_19)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 31; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_19);
+  __Pyx_INCREF(Py_None);
+  PyTuple_SET_ITEM(__pyx_k_tuple_19, 0, Py_None);
+  __Pyx_GIVEREF(Py_None);
+  __Pyx_INCREF(Py_None);
+  PyTuple_SET_ITEM(__pyx_k_tuple_19, 1, Py_None);
+  __Pyx_GIVEREF(Py_None);
+  __Pyx_INCREF(Py_None);
+  PyTuple_SET_ITEM(__pyx_k_tuple_19, 2, Py_None);
+  __Pyx_GIVEREF(Py_None);
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_19));
+
+  /* "_cdec.pyx":38
+ *     def translate(self, sentence, grammar=None):
+ *         if isinstance(sentence, unicode):
+ *             inp = sentence.strip().encode('utf8')             # <<<<<<<<<<<<<<
+ *         elif isinstance(sentence, str):
+ *             inp = sentence.strip()
+ */
+  __pyx_k_tuple_20 = PyTuple_New(1); if (unlikely(!__pyx_k_tuple_20)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 38; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __Pyx_GOTREF(__pyx_k_tuple_20);
+  __Pyx_INCREF(((PyObject *)__pyx_n_s__utf8));
+  PyTuple_SET_ITEM(__pyx_k_tuple_20, 0, ((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_n_s__utf8));
+  __Pyx_GIVEREF(((PyObject *)__pyx_k_tuple_20));
   __Pyx_RefNannyFinishContext();
   return 0;
   __pyx_L1_error:;
@@ -4989,6 +8303,8 @@ static int __Pyx_InitCachedConstants(void) {
 
 static int __Pyx_InitGlobals(void) {
   if (__Pyx_InitStrings(__pyx_string_tab) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 1; __pyx_clineno = __LINE__; goto __pyx_L1_error;};
+  __pyx_int_0 = PyInt_FromLong(0); if (unlikely(!__pyx_int_0)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 1; __pyx_clineno = __LINE__; goto __pyx_L1_error;};
+  __pyx_int_1 = PyInt_FromLong(1); if (unlikely(!__pyx_int_1)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 1; __pyx_clineno = __LINE__; goto __pyx_L1_error;};
   return 0;
   __pyx_L1_error:;
   return -1;
@@ -5061,33 +8377,40 @@ PyMODINIT_FUNC PyInit__cdec(void)
   /*--- Variable export code ---*/
   /*--- Function export code ---*/
   /*--- Type init code ---*/
-  if (PyType_Ready(&__pyx_type_5_cdec_Weights) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 15; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  if (__Pyx_SetAttrString(__pyx_m, "Weights", (PyObject *)&__pyx_type_5_cdec_Weights) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 15; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  __pyx_ptype_5_cdec_Weights = &__pyx_type_5_cdec_Weights;
-  if (PyType_Ready(&__pyx_type_5_cdec_Decoder) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 38; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  if (__Pyx_SetAttrString(__pyx_m, "Decoder", (PyObject *)&__pyx_type_5_cdec_Decoder) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 38; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  __pyx_ptype_5_cdec_Decoder = &__pyx_type_5_cdec_Decoder;
-  if (PyType_Ready(&__pyx_type_5_cdec_Hypergraph) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 71; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  if (__Pyx_SetAttrString(__pyx_m, "Hypergraph", (PyObject *)&__pyx_type_5_cdec_Hypergraph) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 71; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (PyType_Ready(&__pyx_type_5_cdec_DenseVector) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 3; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (__Pyx_SetAttrString(__pyx_m, "DenseVector", (PyObject *)&__pyx_type_5_cdec_DenseVector) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 3; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec_DenseVector = &__pyx_type_5_cdec_DenseVector;
+  if (PyType_Ready(&__pyx_type_5_cdec_SparseVector) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 32; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (__Pyx_SetAttrString(__pyx_m, "SparseVector", (PyObject *)&__pyx_type_5_cdec_SparseVector) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 32; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec_SparseVector = &__pyx_type_5_cdec_SparseVector;
+  if (PyType_Ready(&__pyx_type_5_cdec_Hypergraph) < 0) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 4; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (__Pyx_SetAttrString(__pyx_m, "Hypergraph", (PyObject *)&__pyx_type_5_cdec_Hypergraph) < 0) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 4; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
   __pyx_ptype_5_cdec_Hypergraph = &__pyx_type_5_cdec_Hypergraph;
-  if (PyType_Ready(&__pyx_type_5_cdec_Lattice) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 139; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  if (__Pyx_SetAttrString(__pyx_m, "Lattice", (PyObject *)&__pyx_type_5_cdec_Lattice) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 139; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (PyType_Ready(&__pyx_type_5_cdec_Lattice) < 0) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 3; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (__Pyx_SetAttrString(__pyx_m, "Lattice", (PyObject *)&__pyx_type_5_cdec_Lattice) < 0) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 3; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
   __pyx_ptype_5_cdec_Lattice = &__pyx_type_5_cdec_Lattice;
-  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct____iter__) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 33; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (PyType_Ready(&__pyx_type_5_cdec_Decoder) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 15; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  if (__Pyx_SetAttrString(__pyx_m, "Decoder", (PyObject *)&__pyx_type_5_cdec_Decoder) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 15; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec_Decoder = &__pyx_type_5_cdec_Decoder;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct____iter__) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 18; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
   __pyx_ptype_5_cdec___pyx_scope_struct____iter__ = &__pyx_type_5_cdec___pyx_scope_struct____iter__;
-  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_1_kbest) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 92; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  __pyx_ptype_5_cdec___pyx_scope_struct_1_kbest = &__pyx_type_5_cdec___pyx_scope_struct_1_kbest;
-  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 105; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  __pyx_ptype_5_cdec___pyx_scope_struct_2_kbest_tree = &__pyx_type_5_cdec___pyx_scope_struct_2_kbest_tree;
-  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_3_sample) < 0) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 122; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
-  __pyx_ptype_5_cdec___pyx_scope_struct_3_sample = &__pyx_type_5_cdec___pyx_scope_struct_3_sample;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_1___iter__) < 0) {__pyx_filename = __pyx_f[1]; __pyx_lineno = 43; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec___pyx_scope_struct_1___iter__ = &__pyx_type_5_cdec___pyx_scope_struct_1___iter__;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_2_kbest) < 0) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 32; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec___pyx_scope_struct_2_kbest = &__pyx_type_5_cdec___pyx_scope_struct_2_kbest;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_3_kbest_tree) < 0) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 44; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec___pyx_scope_struct_3_kbest_tree = &__pyx_type_5_cdec___pyx_scope_struct_3_kbest_tree;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_4_sample) < 0) {__pyx_filename = __pyx_f[2]; __pyx_lineno = 56; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec___pyx_scope_struct_4_sample = &__pyx_type_5_cdec___pyx_scope_struct_4_sample;
+  if (PyType_Ready(&__pyx_type_5_cdec___pyx_scope_struct_5___iter__) < 0) {__pyx_filename = __pyx_f[3]; __pyx_lineno = 50; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
+  __pyx_ptype_5_cdec___pyx_scope_struct_5___iter__ = &__pyx_type_5_cdec___pyx_scope_struct_5___iter__;
   /*--- Type import code ---*/
   /*--- Variable import code ---*/
   /*--- Function import code ---*/
   /*--- Execution code ---*/
 
   /* "_cdec.pyx":10
- * cimport kbest as kb
+ * include "lattice.pxi"
  * 
  * SetSilent(True)             # <<<<<<<<<<<<<<
  * 
@@ -5119,7 +8442,7 @@ PyMODINIT_FUNC PyInit__cdec(void)
   /* "_cdec.pyx":1
  * from libcpp.string cimport string             # <<<<<<<<<<<<<<
  * from libcpp.vector cimport vector
- * from cython.operator cimport dereference as deref
+ * from utils cimport *
  */
   __pyx_t_1 = PyDict_New(); if (unlikely(!__pyx_t_1)) {__pyx_filename = __pyx_f[0]; __pyx_lineno = 1; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
   __Pyx_GOTREF(((PyObject *)__pyx_t_1));
@@ -5177,141 +8500,6 @@ static PyObject *__Pyx_GetName(PyObject *dict, PyObject *name) {
     return result;
 }
 
-static void __Pyx_RaiseDoubleKeywordsError(
-    const char* func_name,
-    PyObject* kw_name)
-{
-    PyErr_Format(PyExc_TypeError,
-        #if PY_MAJOR_VERSION >= 3
-        "%s() got multiple values for keyword argument '%U'", func_name, kw_name);
-        #else
-        "%s() got multiple values for keyword argument '%s'", func_name,
-        PyString_AS_STRING(kw_name));
-        #endif
-}
-
-static int __Pyx_ParseOptionalKeywords(
-    PyObject *kwds,
-    PyObject **argnames[],
-    PyObject *kwds2,
-    PyObject *values[],
-    Py_ssize_t num_pos_args,
-    const char* function_name)
-{
-    PyObject *key = 0, *value = 0;
-    Py_ssize_t pos = 0;
-    PyObject*** name;
-    PyObject*** first_kw_arg = argnames + num_pos_args;
-    while (PyDict_Next(kwds, &pos, &key, &value)) {
-        name = first_kw_arg;
-        while (*name && (**name != key)) name++;
-        if (*name) {
-            values[name-argnames] = value;
-        } else {
-            #if PY_MAJOR_VERSION < 3
-            if (unlikely(!PyString_CheckExact(key)) && unlikely(!PyString_Check(key))) {
-            #else
-            if (unlikely(!PyUnicode_Check(key))) {
-            #endif
-                goto invalid_keyword_type;
-            } else {
-                for (name = first_kw_arg; *name; name++) {
-                    #if PY_MAJOR_VERSION >= 3
-                    if (PyUnicode_GET_SIZE(**name) == PyUnicode_GET_SIZE(key) &&
-                        PyUnicode_Compare(**name, key) == 0) break;
-                    #else
-                    if (PyString_GET_SIZE(**name) == PyString_GET_SIZE(key) &&
-                        _PyString_Eq(**name, key)) break;
-                    #endif
-                }
-                if (*name) {
-                    values[name-argnames] = value;
-                } else {
-                    for (name=argnames; name != first_kw_arg; name++) {
-                        if (**name == key) goto arg_passed_twice;
-                        #if PY_MAJOR_VERSION >= 3
-                        if (PyUnicode_GET_SIZE(**name) == PyUnicode_GET_SIZE(key) &&
-                            PyUnicode_Compare(**name, key) == 0) goto arg_passed_twice;
-                        #else
-                        if (PyString_GET_SIZE(**name) == PyString_GET_SIZE(key) &&
-                            _PyString_Eq(**name, key)) goto arg_passed_twice;
-                        #endif
-                    }
-                    if (kwds2) {
-                        if (unlikely(PyDict_SetItem(kwds2, key, value))) goto bad;
-                    } else {
-                        goto invalid_keyword;
-                    }
-                }
-            }
-        }
-    }
-    return 0;
-arg_passed_twice:
-    __Pyx_RaiseDoubleKeywordsError(function_name, **name);
-    goto bad;
-invalid_keyword_type:
-    PyErr_Format(PyExc_TypeError,
-        "%s() keywords must be strings", function_name);
-    goto bad;
-invalid_keyword:
-    PyErr_Format(PyExc_TypeError,
-    #if PY_MAJOR_VERSION < 3
-        "%s() got an unexpected keyword argument '%s'",
-        function_name, PyString_AsString(key));
-    #else
-        "%s() got an unexpected keyword argument '%U'",
-        function_name, key);
-    #endif
-bad:
-    return -1;
-}
-
-static void __Pyx_RaiseArgtupleInvalid(
-    const char* func_name,
-    int exact,
-    Py_ssize_t num_min,
-    Py_ssize_t num_max,
-    Py_ssize_t num_found)
-{
-    Py_ssize_t num_expected;
-    const char *more_or_less;
-    if (num_found < num_min) {
-        num_expected = num_min;
-        more_or_less = "at least";
-    } else {
-        num_expected = num_max;
-        more_or_less = "at most";
-    }
-    if (exact) {
-        more_or_less = "exactly";
-    }
-    PyErr_Format(PyExc_TypeError,
-                 "%s() takes %s %"PY_FORMAT_SIZE_T"d positional argument%s (%"PY_FORMAT_SIZE_T"d given)",
-                 func_name, more_or_less, num_expected,
-                 (num_expected == 1) ? "" : "s", num_found);
-}
-
-static int __Pyx_ArgTypeTest(PyObject *obj, PyTypeObject *type, int none_allowed,
-    const char *name, int exact)
-{
-    if (!type) {
-        PyErr_Format(PyExc_SystemError, "Missing type object");
-        return 0;
-    }
-    if (none_allowed && obj == Py_None) return 1;
-    else if (exact) {
-        if (Py_TYPE(obj) == type) return 1;
-    }
-    else {
-        if (PyObject_TypeCheck(obj, type)) return 1;
-    }
-    PyErr_Format(PyExc_TypeError,
-        "Argument '%s' has incorrect type (expected %s, got %s)",
-        name, type->tp_name, Py_TYPE(obj)->tp_name);
-    return 0;
-}
-
 static CYTHON_INLINE void __Pyx_ErrRestore(PyObject *type, PyObject *value, PyObject *tb) {
 #if CYTHON_COMPILING_IN_CPYTHON
     PyObject *tmp_type, *tmp_value, *tmp_tb;
@@ -5465,6 +8653,141 @@ bad:
 }
 #endif
 
+static int __Pyx_ArgTypeTest(PyObject *obj, PyTypeObject *type, int none_allowed,
+    const char *name, int exact)
+{
+    if (!type) {
+        PyErr_Format(PyExc_SystemError, "Missing type object");
+        return 0;
+    }
+    if (none_allowed && obj == Py_None) return 1;
+    else if (exact) {
+        if (Py_TYPE(obj) == type) return 1;
+    }
+    else {
+        if (PyObject_TypeCheck(obj, type)) return 1;
+    }
+    PyErr_Format(PyExc_TypeError,
+        "Argument '%s' has incorrect type (expected %s, got %s)",
+        name, type->tp_name, Py_TYPE(obj)->tp_name);
+    return 0;
+}
+
+static void __Pyx_RaiseDoubleKeywordsError(
+    const char* func_name,
+    PyObject* kw_name)
+{
+    PyErr_Format(PyExc_TypeError,
+        #if PY_MAJOR_VERSION >= 3
+        "%s() got multiple values for keyword argument '%U'", func_name, kw_name);
+        #else
+        "%s() got multiple values for keyword argument '%s'", func_name,
+        PyString_AS_STRING(kw_name));
+        #endif
+}
+
+static int __Pyx_ParseOptionalKeywords(
+    PyObject *kwds,
+    PyObject **argnames[],
+    PyObject *kwds2,
+    PyObject *values[],
+    Py_ssize_t num_pos_args,
+    const char* function_name)
+{
+    PyObject *key = 0, *value = 0;
+    Py_ssize_t pos = 0;
+    PyObject*** name;
+    PyObject*** first_kw_arg = argnames + num_pos_args;
+    while (PyDict_Next(kwds, &pos, &key, &value)) {
+        name = first_kw_arg;
+        while (*name && (**name != key)) name++;
+        if (*name) {
+            values[name-argnames] = value;
+        } else {
+            #if PY_MAJOR_VERSION < 3
+            if (unlikely(!PyString_CheckExact(key)) && unlikely(!PyString_Check(key))) {
+            #else
+            if (unlikely(!PyUnicode_Check(key))) {
+            #endif
+                goto invalid_keyword_type;
+            } else {
+                for (name = first_kw_arg; *name; name++) {
+                    #if PY_MAJOR_VERSION >= 3
+                    if (PyUnicode_GET_SIZE(**name) == PyUnicode_GET_SIZE(key) &&
+                        PyUnicode_Compare(**name, key) == 0) break;
+                    #else
+                    if (PyString_GET_SIZE(**name) == PyString_GET_SIZE(key) &&
+                        _PyString_Eq(**name, key)) break;
+                    #endif
+                }
+                if (*name) {
+                    values[name-argnames] = value;
+                } else {
+                    for (name=argnames; name != first_kw_arg; name++) {
+                        if (**name == key) goto arg_passed_twice;
+                        #if PY_MAJOR_VERSION >= 3
+                        if (PyUnicode_GET_SIZE(**name) == PyUnicode_GET_SIZE(key) &&
+                            PyUnicode_Compare(**name, key) == 0) goto arg_passed_twice;
+                        #else
+                        if (PyString_GET_SIZE(**name) == PyString_GET_SIZE(key) &&
+                            _PyString_Eq(**name, key)) goto arg_passed_twice;
+                        #endif
+                    }
+                    if (kwds2) {
+                        if (unlikely(PyDict_SetItem(kwds2, key, value))) goto bad;
+                    } else {
+                        goto invalid_keyword;
+                    }
+                }
+            }
+        }
+    }
+    return 0;
+arg_passed_twice:
+    __Pyx_RaiseDoubleKeywordsError(function_name, **name);
+    goto bad;
+invalid_keyword_type:
+    PyErr_Format(PyExc_TypeError,
+        "%s() keywords must be strings", function_name);
+    goto bad;
+invalid_keyword:
+    PyErr_Format(PyExc_TypeError,
+    #if PY_MAJOR_VERSION < 3
+        "%s() got an unexpected keyword argument '%s'",
+        function_name, PyString_AsString(key));
+    #else
+        "%s() got an unexpected keyword argument '%U'",
+        function_name, key);
+    #endif
+bad:
+    return -1;
+}
+
+static void __Pyx_RaiseArgtupleInvalid(
+    const char* func_name,
+    int exact,
+    Py_ssize_t num_min,
+    Py_ssize_t num_max,
+    Py_ssize_t num_found)
+{
+    Py_ssize_t num_expected;
+    const char *more_or_less;
+    if (num_found < num_min) {
+        num_expected = num_min;
+        more_or_less = "at least";
+    } else {
+        num_expected = num_max;
+        more_or_less = "at most";
+    }
+    if (exact) {
+        more_or_less = "exactly";
+    }
+    PyErr_Format(PyExc_TypeError,
+                 "%s() takes %s %"PY_FORMAT_SIZE_T"d positional argument%s (%"PY_FORMAT_SIZE_T"d given)",
+                 func_name, more_or_less, num_expected,
+                 (num_expected == 1) ? "" : "s", num_found);
+}
+
 static CYTHON_INLINE void __Pyx_RaiseNeedMoreValuesError(Py_ssize_t index) {
     PyErr_Format(PyExc_ValueError,
                  "need more than %"PY_FORMAT_SIZE_T"d value%s to unpack",
@@ -5492,6 +8815,8 @@ static int __Pyx_IternextUnpackEndCheck(PyObject *retval, Py_ssize_t expected) {
     return 0;
 }
 
+
+
 static double __Pyx__PyObject_AsDouble(PyObject* obj) {
     PyObject* float_value;
     if (Py_TYPE(obj)->tp_as_number && Py_TYPE(obj)->tp_as_number->nb_float) {
diff --git a/python/src/_cdec.pyx b/python/src/_cdec.pyx
index 664724dd..698a66f6 100644
--- a/python/src/_cdec.pyx
+++ b/python/src/_cdec.pyx
@@ -1,50 +1,28 @@
 from libcpp.string cimport string
 from libcpp.vector cimport vector
-from cython.operator cimport dereference as deref
 from utils cimport *
-cimport hypergraph
 cimport decoder
-cimport lattice
-cimport kbest as kb
+
+include "vectors.pxi"
+include "hypergraph.pxi"
+include "lattice.pxi"
 
 SetSilent(True)
 
 class ParseFailed(Exception):
     pass
 
-cdef class Weights:
-    cdef vector[weight_t]* weights
-
-    def __cinit__(self, Decoder decoder):
-        self.weights = &decoder.dec.CurrentWeightVector()
-
-    def __getitem__(self, char* fname):
-        cdef unsigned fid = FDConvert(fname)
-        if fid <= self.weights.size():
-            return self.weights[0][fid]
-        raise KeyError(fname)
-    
-    def __setitem__(self, char* fname, float value):
-        cdef unsigned fid = FDConvert(<char *>fname)
-        if self.weights.size() <= fid:
-            self.weights.resize(fid + 1)
-        self.weights[0][fid] = value
-
-    def __iter__(self):
-        cdef unsigned fid
-        for fid in range(1, self.weights.size()):
-            yield FDConvert(fid).c_str(), self.weights[0][fid]
-
 cdef class Decoder:
     cdef decoder.Decoder* dec
-    cdef public Weights weights
+    cdef public DenseVector weights
 
     def __cinit__(self, char* config):
         decoder.register_feature_functions()
         cdef istringstream* config_stream = new istringstream(config)
         self.dec = new decoder.Decoder(config_stream)
         del config_stream
-        self.weights = Weights(self)
+        self.weights = DenseVector()
+        self.weights.vector = &self.dec.CurrentWeightVector()
 
     def __dealloc__(self):
         del self.dec
@@ -55,11 +33,17 @@ cdef class Decoder:
                 fname, value = line.split()
                 self.weights[fname.strip()] = float(value)
 
-    # TODO: list, lattice translation
-    def translate(self, unicode sentence, grammar=None):
+    def translate(self, sentence, grammar=None):
+        if isinstance(sentence, unicode):
+            inp = sentence.strip().encode('utf8')
+        elif isinstance(sentence, str):
+            inp = sentence.strip()
+        elif isinstance(sentence, Lattice):
+            inp = str(sentence) # PLF format
+        else:
+            raise TypeError('Cannot translate input type %s' % type(sentence))
         if grammar:
             self.dec.SetSentenceGrammarFromString(string(<char *> grammar))
-        inp = sentence.strip().encode('utf8')
         cdef decoder.BasicObserver observer = decoder.BasicObserver()
         self.dec.Decode(string(<char *>inp), &observer)
         if observer.hypergraph == NULL:
@@ -67,90 +51,3 @@ cdef class Decoder:
         cdef Hypergraph hg = Hypergraph()
         hg.hg = new hypergraph.Hypergraph(observer.hypergraph[0])
         return hg
-    
-cdef class Hypergraph:
-    cdef hypergraph.Hypergraph* hg
-    cdef MT19937* rng
-
-    def __dealloc__(self):
-        del self.hg
-        if self.rng != NULL:
-            del self.rng
-
-    def viterbi(self):
-        assert (self.hg != NULL)
-        cdef vector[WordID] trans
-        hypergraph.ViterbiESentence(self.hg[0], &trans)
-        cdef str sentence = GetString(trans).c_str()
-        return sentence.decode('utf8')
-
-    def viterbi_tree(self):
-        assert (self.hg != NULL)
-        cdef str tree = hypergraph.ViterbiETree(self.hg[0]).c_str()
-        return tree.decode('utf8')
-
-    def kbest(self, size):
-        assert (self.hg != NULL)
-        cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal](self.hg[0], size)
-        cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal].Derivation* derivation
-        cdef str tree
-        cdef unsigned k
-        for k in range(size):
-            derivation = derivations.LazyKthBest(self.hg.nodes_.size() - 1, k)
-            if not derivation: break
-            tree = GetString(derivation._yield).c_str()
-            yield tree.decode('utf8')
-        del derivations
-
-    def kbest_tree(self, size):
-        assert (self.hg != NULL)
-        cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ETreeTraversal](self.hg[0], size)
-        cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal].Derivation* derivation
-        cdef str sentence
-        cdef unsigned k
-        for k in range(size):
-            derivation = derivations.LazyKthBest(self.hg.nodes_.size() - 1, k)
-            if not derivation: break
-            sentence = GetString(derivation._yield).c_str()
-            yield sentence.decode('utf8')
-        del derivations
-
-    def intersect(self, Lattice lat):
-        assert (self.hg != NULL)
-        hypergraph.Intersect(lat.lattice[0], self.hg)
-
-    def sample(self, unsigned n):
-        assert (self.hg != NULL)
-        cdef vector[hypergraph.Hypothesis]* hypos = new vector[hypergraph.Hypothesis]()
-        if self.rng == NULL:
-            self.rng = new MT19937()
-        hypergraph.sample_hypotheses(self.hg[0], n, self.rng, hypos)
-        cdef str sentence
-        cdef unsigned k
-        for k in range(hypos.size()):
-            sentence = GetString(hypos[0][k].words).c_str()
-            yield sentence.decode('utf8')
-        del hypos
-
-    # TODO: get feature expectations, get partition function ("inside" score)
-    # TODO: reweight the forest with different weights (Hypergraph::Reweight)
-    # TODO: inside-outside pruning
-
-cdef class Lattice:
-    cdef lattice.Lattice* lattice
-
-    def __init__(self, tuple plf_tuple):
-        self.lattice = new lattice.Lattice()
-        cdef bytes plf = str(plf_tuple)
-        hypergraph.PLFtoLattice(string(<char *>plf), self.lattice)
-
-    def __str__(self):
-        return hypergraph.AsPLF(self.lattice[0]).c_str()
-
-    def __iter__(self):
-        return iter(eval(str(self)))
-
-    def __dealloc__(self):
-        del self.lattice
-
-# TODO: wrap SparseVector
diff --git a/python/src/decoder.pxd b/python/src/decoder.pxd
index ab858841..e2678151 100644
--- a/python/src/decoder.pxd
+++ b/python/src/decoder.pxd
@@ -4,7 +4,7 @@ from hypergraph cimport Hypergraph
 from utils cimport istream, weight_t
 
 cdef extern from "decoder/ff_register.h":
-    cdef void register_feature_functions()
+    void register_feature_functions()
 
 cdef extern from "decoder/decoder.h":
     cdef cppclass SentenceMetadata:
@@ -16,20 +16,20 @@ cdef extern from "decoder/decoder.h":
     cdef cppclass Decoder:
         Decoder(int argc, char** argv)
         Decoder(istream* config_file)
-        bint Decode(string input, DecoderObserver* observer)
+        bint Decode(string& inp, DecoderObserver* observer)
 
         # access this to either *read* or *write* to the decoder's last
         # weight vector (i.e., the weights of the finest past)
         vector[weight_t]& CurrentWeightVector()
 
-        void SetId(int id)
-        #const boost::program_options::variables_map& GetConf() const { return conf }
+        # void SetId(int id)
+        # const boost::program_options::variables_map& GetConf() const { return conf }
 
         # add grammar rules (currently only supported by SCFG decoders)
         # that will be used on subsequent calls to Decode. rules should be in standard
         # text format. This function does NOT read from a file.
-        void SetSupplementalGrammar(string grammar)
-        void SetSentenceGrammarFromString(string grammar_str)
+        void SetSupplementalGrammar(string& grammar)
+        void SetSentenceGrammarFromString(string& grammar_str)
 
 cdef extern from "observer.h":
     cdef cppclass BasicObserver(DecoderObserver):
diff --git a/python/src/hypergraph.pxd b/python/src/hypergraph.pxd
index 4aef6955..656b1d47 100644
--- a/python/src/hypergraph.pxd
+++ b/python/src/hypergraph.pxd
@@ -1,41 +1,73 @@
 from libcpp.string cimport string
 from libcpp.vector cimport vector
 from utils cimport *
-cimport lattice
+from lattice cimport Lattice
 
 cdef extern from "decoder/hg.h":
+    cdef cppclass EdgeMask "std::vector<bool>":
+        EdgeMask(int size)
+        bint& operator[](int)
+
     cdef cppclass Hypergraph:
+        cppclass Edge:
+            int id_
+            int head_node_ # position in hg.nodes_
+            SmallVector[unsigned] tail_nodes_ # positions in hg.nodes_
+            #TRulePtr rule_
+            FastSparseVector[weight_t] feature_values_
+            LogVal[double] edge_prob_
+            short int i_
+            short int j_
+            short int prev_i_
+            short int prev_j_
         cppclass Node:
             int id_
             WordID cat_
             WordID NT()
-            #EdgesVector in_edges_
-            #EdgesVector out_edges_
+            vector[Edge] in_edges_
+            vector[Edge] out_edges_
         Hypergraph(Hypergraph)
         vector[Node] nodes_
+        vector[Edge] edges_
+        void Reweight(vector[weight_t]& weights)
+        void Reweight(FastSparseVector& weights)
+        bint PruneInsideOutside(double beam_alpha,
+                                double density,
+                                EdgeMask* preserve_mask,
+                                bint use_sum_prod_semiring,
+                                double scale,
+                                bint safe_inside)
 
 cdef extern from "decoder/viterbi.h":
-    cdef prob_t ViterbiESentence(Hypergraph hg, vector[WordID]* trans)
-    cdef string ViterbiETree(Hypergraph hg)
+    LogVal[double] ViterbiESentence(Hypergraph& hg, vector[WordID]* trans)
+    string ViterbiETree(Hypergraph& hg)
+    LogVal[double] ViterbiFSentence(Hypergraph& hg, vector[WordID]* trans)
+    string ViterbiFTree(Hypergraph& hg)
+    FastSparseVector[weight_t] ViterbiFeatures(Hypergraph& hg)
+    FastSparseVector[weight_t] ViterbiFeatures(Hypergraph& hg, 
+            FastSparseVector[weight_t]* weights,
+            bint fatal_dotprod_disagreement)
 
 cdef extern from "decoder/hg_io.h" namespace "HypergraphIO":
     bint ReadFromJSON(istream* inp, Hypergraph* out)
-    bint WriteToJSON(Hypergraph hg, bint remove_rules, ostream* out)
-
-    #void WriteAsCFG(Hypergraph hg)
-    #void WriteTarget(string base, unsigned sent_id, Hypergraph hg)
-
-    void ReadFromPLF(string inp, Hypergraph* out, int line=*)
-    string AsPLF(Hypergraph hg, bint include_global_parentheses=*)
-    string AsPLF(lattice.Lattice lat, bint include_global_parentheses=*)
-    void PLFtoLattice(string plf, lattice.Lattice* pl)
+    bint WriteToJSON(Hypergraph& hg, bint remove_rules, ostream* out)
+    void ReadFromPLF(string& inp, Hypergraph* out, int line)
+    string AsPLF(Hypergraph& hg, bint include_global_parentheses)
+    void PLFtoLattice(string& plf, Lattice* pl)
+    string AsPLF(Lattice& lat, bint include_global_parentheses)
 
 cdef extern from "decoder/hg_intersect.h" namespace "HG":
-    bint Intersect(lattice.Lattice target, Hypergraph* hg)
+    bint Intersect(Lattice& target, Hypergraph* hg)
 
 cdef extern from "decoder/hg_sampler.h" namespace "HypergraphSampler":
     cdef cppclass Hypothesis:
         vector[WordID] words
-        SparseVector[double] fmap
-        prob_t model_score
-    void sample_hypotheses(Hypergraph hg, unsigned n, MT19937* rng, vector[Hypothesis]* hypos)
+        FastSparseVector[double] fmap
+        LogVal[double] model_score
+    void sample_hypotheses(Hypergraph& hg, 
+                           unsigned n, 
+                           MT19937* rng, 
+                           vector[Hypothesis]* hypos)
+
+cdef extern from "decoder/csplit.h" namespace "CompoundSplit":
+    int GetFullWordEdgeIndex(Hypergraph& forest)
diff --git a/python/src/hypergraph.pxi b/python/src/hypergraph.pxi
new file mode 100644
index 00000000..c226d105
--- /dev/null
+++ b/python/src/hypergraph.pxi
@@ -0,0 +1,92 @@
+cimport hypergraph
+cimport kbest as kb
+
+cdef class Hypergraph:
+    cdef hypergraph.Hypergraph* hg
+    cdef MT19937* rng
+
+    def __dealloc__(self):
+        del self.hg
+        if self.rng != NULL:
+            del self.rng
+
+    def viterbi(self):
+        cdef vector[WordID] trans
+        hypergraph.ViterbiESentence(self.hg[0], &trans)
+        cdef str sentence = GetString(trans).c_str()
+        return sentence.decode('utf8')
+
+    def viterbi_tree(self):
+        cdef str tree = hypergraph.ViterbiETree(self.hg[0]).c_str()
+        return tree.decode('utf8')
+
+    def viterbi_source_tree(self):
+        cdef str tree = hypergraph.ViterbiFTree(self.hg[0]).c_str()
+        return tree.decode('utf8')
+    
+    def viterbi_features(self):
+        cdef SparseVector fmap = SparseVector()
+        fmap.vector = new FastSparseVector[weight_t](hypergraph.ViterbiFeatures(self.hg[0]))
+        return fmap
+
+    def kbest(self, size):
+        cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal](self.hg[0], size)
+        cdef kb.KBestDerivations[vector[WordID], kb.ESentenceTraversal].Derivation* derivation
+        cdef str sentence
+        cdef unsigned k
+        for k in range(size):
+            derivation = derivations.LazyKthBest(self.hg.nodes_.size() - 1, k)
+            if not derivation: break
+            sentence = GetString(derivation._yield).c_str()
+            yield sentence.decode('utf8')
+        del derivations
+
+    def kbest_tree(self, size):
+        cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal]* derivations = new kb.KBestDerivations[vector[WordID], kb.ETreeTraversal](self.hg[0], size)
+        cdef kb.KBestDerivations[vector[WordID], kb.ETreeTraversal].Derivation* derivation
+        cdef str tree
+        cdef unsigned k
+        for k in range(size):
+            derivation = derivations.LazyKthBest(self.hg.nodes_.size() - 1, k)
+            if not derivation: break
+            tree = GetString(derivation._yield).c_str()
+            yield tree.decode('utf8')
+        del derivations
+
+    def sample(self, unsigned n):
+        cdef vector[hypergraph.Hypothesis]* hypos = new vector[hypergraph.Hypothesis]()
+        if self.rng == NULL:
+            self.rng = new MT19937()
+        hypergraph.sample_hypotheses(self.hg[0], n, self.rng, hypos)
+        cdef str sentence
+        cdef unsigned k
+        for k in range(hypos.size()):
+            sentence = GetString(hypos[0][k].words).c_str()
+            yield sentence.decode('utf8')
+        del hypos
+
+    # TODO richer k-best/sample output (feature vectors, trees?)
+
+    def intersect(self, Lattice lat):
+        return hypergraph.Intersect(lat.lattice[0], self.hg)
+
+    def prune(self, beam_alpha=0, density=0, **kwargs):
+        cdef hypergraph.EdgeMask* preserve_mask = NULL
+        if 'csplit_preserve_full_word' in kwargs:
+             preserve_mask = new hypergraph.EdgeMask(self.hg.edges_.size())
+             preserve_mask[0][hypergraph.GetFullWordEdgeIndex(self.hg[0])] = True
+        self.hg.PruneInsideOutside(beam_alpha, density, preserve_mask, False, 1, False)
+
+    def lattice(self): # TODO direct hg -> lattice conversion in cdec
+        cdef str plf = hypergraph.AsPLF(self.hg[0], True).c_str()
+        return Lattice(eval(plf))
+
+    def reweight(self, weights):
+        if isinstance(weights, SparseVector):
+            self.hg.Reweight((<SparseVector> weights).vector[0])
+        elif isinstance(weights, DenseVector):
+            self.hg.Reweight((<DenseVector> weights).vector[0])
+        else:
+            raise ValueError('cannot reweight hypergraph with %s' % type(weights))
+
+    # TODO get feature expectations, get partition function ("inside" score)
diff --git a/python/src/kbest.pxd b/python/src/kbest.pxd
index e339714a..f34ac5ed 100644
--- a/python/src/kbest.pxd
+++ b/python/src/kbest.pxd
@@ -1,16 +1,18 @@
 from libcpp.vector cimport vector
 from utils cimport WordID
-cimport hypergraph
+from hypergraph cimport Hypergraph
 
 cdef extern from "decoder/viterbi.h":
     cdef cppclass ESentenceTraversal:
         pass
     cdef cppclass ETreeTraversal:
         pass
+    cdef cppclass FTreeTraversal:
+        pass
 
 cdef extern from "decoder/kbest.h" namespace "KBest":
     cdef cppclass KBestDerivations[T, Traversal]:
         cppclass Derivation:
             T _yield "yield"
-        KBestDerivations(hypergraph.Hypergraph hg, unsigned k)
+        KBestDerivations(Hypergraph& hg, unsigned k)
         Derivation* LazyKthBest(unsigned v, unsigned k)
diff --git a/python/src/lattice.pxd b/python/src/lattice.pxd
index bdfaba80..3a4bc22f 100644
--- a/python/src/lattice.pxd
+++ b/python/src/lattice.pxd
@@ -1,4 +1,5 @@
 from libcpp.vector cimport vector
+from libcpp.string cimport string
 from utils cimport WordID
 
 cdef extern from "decoder/lattice.h":
@@ -9,8 +10,12 @@ cdef extern from "decoder/lattice.h":
         LatticeArc()
         LatticeArc(WordID w, double c, int i)
 
-    cdef cppclass Lattice: # (vector[vector[LatticeArc]])
+    cdef cppclass Lattice(vector): # (vector[vector[LatticeArc]])
         Lattice()
         Lattice(unsigned t)
-        Lattice(unsigned t, vector[LatticeArc] v)
+        Lattice(unsigned t, vector[LatticeArc]& v)
         bint IsSentence()
+        vector[LatticeArc]& operator[](unsigned)
+
+cdef extern from "decoder/lattice.h" namespace "LatticeTools":
+    void ConvertTextToLattice(string& text, Lattice* pl)
diff --git a/python/src/lattice.pxi b/python/src/lattice.pxi
new file mode 100644
index 00000000..493c6dcd
--- /dev/null
+++ b/python/src/lattice.pxi
@@ -0,0 +1,56 @@
+cimport lattice
+
+cdef class Lattice:
+    cdef lattice.Lattice* lattice
+
+    def __init__(self, inp):
+        if isinstance(inp, tuple):
+            self.lattice = new lattice.Lattice(len(inp))
+            for i, arcs in enumerate(inp):
+                self[i] = arcs
+        else:
+            if isinstance(inp, unicode):
+                inp = inp.encode('utf8')
+            if not isinstance(inp, str):
+                raise TypeError('Cannot create lattice from %s' % type(inp))
+            self.lattice = new lattice.Lattice()
+            lattice.ConvertTextToLattice(string(<char *>inp), self.lattice)
+
+    def __getitem__(self, int index):
+        if not 0 <= index < len(self):
+            raise IndexError('lattice index out of range')
+        arcs = []
+        cdef vector[lattice.LatticeArc] arc_vector = self.lattice[0][index]
+        cdef lattice.LatticeArc* arc
+        cdef str label
+        cdef unsigned i
+        for i in range(arc_vector.size()):
+            arc = &arc_vector[i]
+            label = TDConvert(arc.label)
+            arcs.append((label.decode('utf8'), arc.cost, arc.dist2next))
+        return tuple(arcs)
+
+    def __setitem__(self, int index, tuple arcs):
+        if not 0 <= index < len(self):
+            raise IndexError('lattice index out of range')
+        cdef lattice.LatticeArc* arc
+        for (label, cost, dist2next) in arcs:
+            if isinstance(label, unicode):
+                label = label.encode('utf8')
+            arc = new lattice.LatticeArc(TDConvert(<char *>label), cost, dist2next)
+            self.lattice[0][index].push_back(arc[0])
+            del arc
+
+    def __len__(self):
+        return self.lattice.size()
+
+    def __str__(self):
+        return hypergraph.AsPLF(self.lattice[0], True).c_str()
+
+    def __iter__(self):
+        cdef unsigned i
+        for i in range(len(self)):
+            yield self[i]
+
+    def __dealloc__(self):
+        del self.lattice
diff --git a/python/src/utils.pxd b/python/src/utils.pxd
index 786cd265..3d518524 100644
--- a/python/src/utils.pxd
+++ b/python/src/utils.pxd
@@ -1,5 +1,6 @@
 from libcpp.string cimport string
 from libcpp.vector cimport vector
+from libcpp.pair cimport pair
 
 cdef extern from "<iostream>" namespace "std":
     cdef cppclass istream:
@@ -8,30 +9,60 @@ cdef extern from "<iostream>" namespace "std":
         pass
     cdef cppclass istringstream(istream):
         istringstream(char*)
+    ostream cout
 
 cdef extern from "utils/weights.h":
     ctypedef double weight_t
 
 cdef extern from "utils/logval.h":
     cdef cppclass LogVal[T]:
-        pass
+        double as_float()
 
-cdef extern from "utils/prob.h":
-    cdef cppclass prob_t:
-        pass
+    double log(LogVal[double]&)
 
 cdef extern from "utils/wordid.h":
     ctypedef int WordID
 
-cdef extern from "utils/sparse_vector.h":
-    cdef cppclass SparseVector[T]:
+cdef extern from "utils/small_vector.h":
+    cdef cppclass SmallVector[T]:
         pass
 
+cdef extern from "utils/sparse_vector.h":
+    cdef cppclass FastSparseVector[T]:
+        cppclass const_iterator:
+            const_iterator(FastSparseVector[T]&, bint is_end)
+            pair[unsigned, T]* ptr "operator->" ()
+            const_iterator& operator++()
+            bint operator==(const_iterator&)
+            bint operator!=(const_iterator&)
+        FastSparseVector()
+        FastSparseVector(FastSparseVector[T]&)
+        const_iterator begin()
+        const_iterator end()
+        void init_vector(vector[T]* vp)
+        T value(unsigned k)
+        void set_value(unsigned k, T& v)
+        size_t size()
+        bint nonzero(unsigned k)
+        bint operator==(FastSparseVector[T]&)
+        T dot(vector[weight_t]&) # cython bug when [T]
+        T dot(FastSparseVector[T]&)
+
+    FastSparseVector[weight_t] operator+(FastSparseVector[weight_t]&, FastSparseVector[weight_t]&)
+    FastSparseVector[weight_t] operator-(FastSparseVector[weight_t]&, FastSparseVector[weight_t]&)
+    ostream operator<<(ostream& out, FastSparseVector[weight_t]& v)
+
+cdef extern from "utils/weights.h" namespace "Weights":
+    void InitSparseVector(vector[weight_t]& dv, FastSparseVector[weight_t]* sv)
+
 cdef extern from "utils/tdict.cc" namespace "TD":
-    cdef string GetString(vector[WordID] st)
+    string GetString(vector[WordID]& st)
+    unsigned NumWords()
+    WordID TDConvert "TD::Convert" (char*)
+    char* TDConvert "TD::Convert" (WordID)
 
 cdef extern from "utils/verbose.h":
-    cdef void SetSilent(bint)
+    void SetSilent(bint)
 
 cdef extern from "utils/fdict.h" namespace "FD":
     WordID FDConvert "FD::Convert" (char*)
@@ -39,15 +70,9 @@ cdef extern from "utils/fdict.h" namespace "FD":
 
 cdef extern from "utils/filelib.h":
     cdef cppclass ReadFile:
-        ReadFile(string)
+        ReadFile(string&)
         istream* stream()
 
 cdef extern from "utils/sampler.h":
     cdef cppclass MT19937:
         pass
-
-"""
-cdef extern from "<boost/shared_ptr.hpp>" namespace "boost":
-    cdef cppclass shared_ptr[T]:
-        void reset(T*)
-"""
diff --git a/python/src/vectors.pxi b/python/src/vectors.pxi
new file mode 100644
index 00000000..74d3a0bd
--- /dev/null
+++ b/python/src/vectors.pxi
@@ -0,0 +1,101 @@
+from cython.operator cimport preincrement as pinc
+
+cdef class DenseVector:
+    cdef vector[weight_t]* vector
+
+    def __getitem__(self, char* fname):
+        cdef unsigned fid = FDConvert(fname)
+        if fid <= self.vector.size():
+            return self.vector[0][fid]
+        raise KeyError(fname)
+    
+    def __setitem__(self, char* fname, float value):
+        cdef unsigned fid = FDConvert(<char *>fname)
+        if self.vector.size() <= fid:
+            self.vector.resize(fid + 1)
+        self.vector[0][fid] = value
+
+    def __iter__(self):
+        cdef unsigned fid
+        for fid in range(1, self.vector.size()):
+            yield FDConvert(fid).c_str(), self.vector[0][fid]
+
+    def dot(self, SparseVector other):
+        return other.dot(self)
+
+    def tosparse(self):
+        cdef SparseVector sparse = SparseVector()
+        sparse.vector = new FastSparseVector[weight_t]()
+        InitSparseVector(self.vector[0], sparse.vector)
+        return sparse
+
+cdef class SparseVector:
+    cdef FastSparseVector[weight_t]* vector
+
+    def __getitem__(self, char* fname):
+        cdef unsigned fid = FDConvert(fname)
+        return self.vector.value(fid)
+    
+    def __setitem__(self, char* fname, float value):
+        cdef unsigned fid = FDConvert(<char *>fname)
+        self.vector.set_value(fid, value)
+
+    def __iter__(self):
+        cdef FastSparseVector[weight_t].const_iterator* it = new FastSparseVector[weight_t].const_iterator(self.vector[0], False)
+        cdef str fname
+        for i in range(self.vector.size()):
+            fname = FDConvert(it[0].ptr().first).c_str()
+            yield (fname, it[0].ptr().second)
+            pinc(it[0])
+
+    def dot(self, other):
+        if isinstance(other, DenseVector):
+            return self.vector.dot((<DenseVector> other).vector[0])
+        elif isinstance(other, SparseVector):
+            return self.vector.dot((<SparseVector> other).vector[0])
+        raise ValueError('cannot take the dot product of %s and SparseVector' % type(other))
+
+    def todense(self):
+        cdef DenseVector dense = DenseVector()
+        dense.vector = new vector[weight_t]()
+        self.vector.init_vector(dense.vector)
+        return dense
+    
+    def __richcmp__(SparseVector self, SparseVector other, int op):
+        if op == 2: # ==
+            return self.vector[0] == other.vector[0]
+        elif op == 3: # !=
+            return not (self == other)
+        raise NotImplemented('comparison not implemented for SparseVector')
+
+    def __len__(self):
+        return self.vector.size()
+
+    def __contains__(self, char* fname):
+        return self.vector.nonzero(FDConvert(fname))
+    
+    def __iadd__(SparseVector self, SparseVector other):
+        self.vector[0] += other.vector[0]
+        return self
+
+    def __isub__(SparseVector self, SparseVector other):
+        self.vector[0] -= other.vector[0]
+        return self
+
+    def __imul__(SparseVector self, float scalar):
+        self.vector[0] *= scalar
+        return self
+
+    def __idiv__(SparseVector self, float scalar):
+        self.vector[0] /= scalar
+        return self
+
+    def __add__(SparseVector self, SparseVector other):
+        cdef SparseVector result = SparseVector()
+        result.vector = new FastSparseVector[weight_t](self.vector[0] + other.vector[0])
+        return result
+
+    def __sub__(SparseVector self, SparseVector other):
+        cdef SparseVector result = SparseVector()
+        result.vector = new FastSparseVector[weight_t](self.vector[0] - other.vector[0])
+        return result