1 files changed, 79 insertions, 0 deletions
diff --git a/vest/viterbi_envelope.h b/vest/viterbi_envelope.h
new file mode 100644
index 00000000..39d2b537
--- /dev/null
+++ b/vest/viterbi_envelope.h
@@ -0,0 +1,79 @@
+#ifndef _VITERBI_ENVELOPE_H_
+#define _VITERBI_ENVELOPE_H_
+
+#include <vector>
+#include <iostream>
+#include <boost/shared_ptr.hpp>
+
+#include "hg.h"
+#include "sparse_vector.h"
+
+static const double kMinusInfinity = -std::numeric_limits<double>::infinity();
+static const double kPlusInfinity = std::numeric_limits<double>::infinity();
+
+struct Segment {
+  Segment() : x(), m(), b() {}
+  Segment(double _m, double _b) :
+    x(kMinusInfinity), m(_m), b(_b) {}
+  Segment(double _x, double _m, double _b, const boost::shared_ptr<Segment>& p1_, const boost::shared_ptr<Segment>& p2_) :
+    x(_x), m(_m), b(_b), p1(p1_), p2(p2_) {}
+  Segment(double _m, double _b, TRulePtr _rule) :
+    x(kMinusInfinity), m(_m), b(_b), rule(_rule) {}
+
+  double x;                   // x intersection with previous segment in env, or -inf if none
+  double m;                   // this line's slope
+  double b;                   // intercept with y-axis
+
+  // we keep a pointer to the "parents" of this segment so we can reconstruct
+  // the Viterbi translation corresponding to this segment
+  boost::shared_ptr<Segment> p1;
+  boost::shared_ptr<Segment> p2;
+
+  // only Segments created from an edge using the ViterbiEnvelopeWeightFunction
+  // have rules
+  TRulePtr rule;
+
+  // recursively recover the Viterbi translation that will result from setting
+  // the weights to origin + axis * x, where x is any value from this->x up
+  // until the next largest x in the containing ViterbiEnvelope
+  void ConstructTranslation(std::vector<WordID>* trans) const;
+};
+
+// this is the semiring value type,
+// it defines constructors for 0, 1, and the operations + and *
+struct ViterbiEnvelope {
+  // create semiring zero
+  ViterbiEnvelope() : is_sorted(true) {}  // zero
+  // for debugging:
+  ViterbiEnvelope(const std::vector<boost::shared_ptr<Segment> >& s) : segs(s) { Sort(); }
+  // create semiring 1 or 0
+  explicit ViterbiEnvelope(int i);
+  ViterbiEnvelope(int n, Segment* seg) : is_sorted(true), segs(n, boost::shared_ptr<Segment>(seg)) {}
+  const ViterbiEnvelope& operator+=(const ViterbiEnvelope& other);
+  const ViterbiEnvelope& operator*=(const ViterbiEnvelope& other);
+  bool IsMultiplicativeIdentity() const {
+    return size() == 1 && (segs[0]->b == 0.0 && segs[0]->m == 0.0) && (!segs[0]->rule); }
+  const std::vector<boost::shared_ptr<Segment> >& GetSortedSegs() const {
+    if (!is_sorted) Sort();
+    return segs;
+  }
+  size_t size() const { return segs.size(); }
+
+ private:
+  bool IsEdgeEnvelope() const {
+    return segs.size() == 1 && segs[0]->rule; }
+  void Sort() const;
+  mutable bool is_sorted;
+  mutable std::vector<boost::shared_ptr<Segment> > segs;
+};
+std::ostream& operator<<(std::ostream& os, const ViterbiEnvelope& env);
+
+struct ViterbiEnvelopeWeightFunction {
+  ViterbiEnvelopeWeightFunction(const SparseVector<double>& ori,
+                                const SparseVector<double>& dir) : origin(ori), direction(dir) {}
+  ViterbiEnvelope operator()(const Hypergraph::Edge& e) const;
+  const SparseVector<double> origin;
+  const SparseVector<double> direction;
+};
+
+#endif