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authorChris Dyer <redpony@gmail.com>2014-03-18 01:41:17 -0400
committerChris Dyer <redpony@gmail.com>2014-03-18 01:41:17 -0400
commit606e3e38b8a830dbbe65963ebf6c5ce7866b7800 (patch)
tree332cec5e0b4c8e3b8d6cc0d631fe5d5815f088f6 /utils
parentcc87bfed0697583b7c11243913254dde3c0047d4 (diff)
star function
Diffstat (limited to 'utils')
-rw-r--r--utils/Makefile.am2
-rw-r--r--utils/exp_semiring.h64
-rw-r--r--utils/logval.h12
-rw-r--r--utils/star.h12
4 files changed, 90 insertions, 0 deletions
diff --git a/utils/Makefile.am b/utils/Makefile.am
index a22b6727..c0ce3509 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -27,6 +27,7 @@ libutils_a_SOURCES = \
citycrc.h \
corpus_tools.h \
dict.h \
+ exp_semiring.h \
fast_sparse_vector.h \
fdict.h \
feature_vector.h \
@@ -49,6 +50,7 @@ libutils_a_SOURCES = \
show.h \
small_vector.h \
sparse_vector.h \
+ star.h \
static_utoa.h \
stringlib.h \
tdict.h \
diff --git a/utils/exp_semiring.h b/utils/exp_semiring.h
new file mode 100644
index 00000000..7572ccf5
--- /dev/null
+++ b/utils/exp_semiring.h
@@ -0,0 +1,64 @@
+#ifndef _EXP_SEMIRING_H_
+#define _EXP_SEMIRING_H_
+
+#include <iostream>
+#include "star.h"
+
+// this file implements the first-order expectation semiring described
+// in Li & Eisner (EMNLP 2009)
+
+// requirements:
+// RType * RType ==> RType
+// PType * PType ==> PType
+// RType * PType ==> RType
+// good examples:
+// PType scalar, RType vector
+// BAD examples:
+// PType vector, RType scalar
+template <class PType, class RType>
+struct PRPair {
+ PRPair() : p(), r() {}
+ // Inside algorithm requires that T(0) and T(1)
+ // return the 0 and 1 values of the semiring
+ explicit PRPair(double x) : p(x), r() {}
+ PRPair(const PType& p, const RType& r) : p(p), r(r) {}
+ PRPair& operator+=(const PRPair& o) {
+ p += o.p;
+ r += o.r;
+ return *this;
+ }
+ PRPair& operator*=(const PRPair& o) {
+ r = (o.r * p) + (o.p * r);
+ p *= o.p;
+ return *this;
+ }
+ PType p;
+ RType r;
+};
+
+template <class P, class R>
+std::ostream& operator<<(std::ostream& o, const PRPair<P,R>& x) {
+ return o << '<' << x.p << ", " << x.r << '>';
+}
+
+template <class P, class R>
+const PRPair<P,R> operator+(const PRPair<P,R>& a, const PRPair<P,R>& b) {
+ PRPair<P,R> result = a;
+ result += b;
+ return result;
+}
+
+template <class P, class R>
+const PRPair<P,R> operator*(const PRPair<P,R>& a, const PRPair<P,R>& b) {
+ PRPair<P,R> result = a;
+ result *= b;
+ return result;
+}
+
+template <class P, class R>
+const PRPair<P,R> star(const PRPair<P,R>& x) {
+ const P pstar = star(x.p);
+ return PRPair<P,R>(pstar, pstar * x.r * pstar);
+}
+
+#endif
diff --git a/utils/logval.h b/utils/logval.h
index ec1f6acd..7f1e1024 100644
--- a/utils/logval.h
+++ b/utils/logval.h
@@ -11,6 +11,7 @@
#include <cassert>
#include "semiring.h"
#include "show.h"
+#include "star.h"
//TODO: template for supporting negation or not - most uses are for nonnegative "probs" only; probably some 10-20% speedup available
template <class T>
@@ -242,4 +243,15 @@ bool operator>=(const LogVal<T>& lhs, const LogVal<T>& rhs) {
template <class T>
std::size_t hash_value(const LogVal<T>& x) { return x.hash_impl(); }
+template <class T>
+LogVal<T> star(LogVal<T> x) {
+ if (x.is_0()) return x;
+ if (x.v_ >= 0) {
+ x.v_ = std::numeric_limits<T>::infinity();
+ } else {
+ x.v_ = -log1p(-x.as_float());
+ }
+ return x;
+}
+
#endif
diff --git a/utils/star.h b/utils/star.h
new file mode 100644
index 00000000..3295112c
--- /dev/null
+++ b/utils/star.h
@@ -0,0 +1,12 @@
+#ifndef _STAR_H_
+#define _STAR_H_
+
+template <typename T>
+T star(const T& x) {
+ if (!x) return T();
+ if (x > T(1)) return std::numeric_limits<T>::infinity();
+ if (x < -T(1)) return -std::numeric_limits<T>::infinity();
+ return T(1) / (T(1) - x);
+}
+
+#endif