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#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
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