mirror of
https://github.com/moses-smt/mosesdecoder.git
synced 2024-12-28 14:32:38 +03:00
132 lines
4.1 KiB
C++
132 lines
4.1 KiB
C++
/***********************************************************************
|
|
Moses - statistical machine translation system
|
|
Copyright (C) 2006-2014 University of Edinburgh
|
|
|
|
This library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
This library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with this library; if not, write to the Free Software
|
|
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
***********************************************************************/
|
|
|
|
#pragma once
|
|
|
|
#include <cassert>
|
|
#include "ChartHypothesis.h"
|
|
#include "ScoreComponentCollection.h"
|
|
#include "FF/InternalTree.h"
|
|
|
|
#include <boost/unordered_set.hpp>
|
|
#include <boost/weak_ptr.hpp>
|
|
|
|
#include <queue>
|
|
#include <vector>
|
|
|
|
namespace Moses
|
|
{
|
|
|
|
// k-best list extractor that implements algorithm 3 from this paper:
|
|
//
|
|
// Liang Huang and David Chiang
|
|
// "Better k-best parsing"
|
|
// In Proceedings of IWPT 2005
|
|
//
|
|
class ChartKBestExtractor
|
|
{
|
|
public:
|
|
struct Vertex;
|
|
|
|
struct UnweightedHyperarc {
|
|
boost::shared_ptr<Vertex> head;
|
|
std::vector<boost::shared_ptr<Vertex> > tail;
|
|
};
|
|
|
|
struct Derivation {
|
|
Derivation(const UnweightedHyperarc &);
|
|
Derivation(const Derivation &, std::size_t);
|
|
|
|
UnweightedHyperarc edge;
|
|
std::vector<std::size_t> backPointers;
|
|
std::vector<boost::shared_ptr<Derivation> > subderivations;
|
|
ScoreComponentCollection scoreBreakdown;
|
|
float score;
|
|
};
|
|
|
|
struct DerivationOrderer {
|
|
bool operator()(const boost::weak_ptr<Derivation> &d1,
|
|
const boost::weak_ptr<Derivation> &d2) const {
|
|
boost::shared_ptr<Derivation> s1(d1);
|
|
boost::shared_ptr<Derivation> s2(d2);
|
|
return s1->score < s2->score;
|
|
}
|
|
};
|
|
|
|
struct Vertex {
|
|
typedef std::priority_queue<boost::weak_ptr<Derivation>,
|
|
std::vector<boost::weak_ptr<Derivation> >,
|
|
DerivationOrderer> DerivationQueue;
|
|
|
|
Vertex(const ChartHypothesis &h) : hypothesis(h), visited(false) {}
|
|
|
|
const ChartHypothesis &hypothesis;
|
|
std::vector<boost::weak_ptr<Derivation> > kBestList;
|
|
DerivationQueue candidates;
|
|
bool visited;
|
|
};
|
|
|
|
typedef std::vector<boost::shared_ptr<Derivation> > KBestVec;
|
|
|
|
// Extract the k-best list from the search hypergraph given the full, sorted
|
|
// list of top-level vertices.
|
|
void Extract(const std::vector<const ChartHypothesis*> &topHypos,
|
|
std::size_t k, KBestVec &);
|
|
|
|
static Phrase GetOutputPhrase(const Derivation &);
|
|
static TreePointer GetOutputTree(const Derivation &);
|
|
|
|
private:
|
|
typedef boost::unordered_map<const ChartHypothesis *,
|
|
boost::shared_ptr<Vertex> > VertexMap;
|
|
|
|
struct DerivationHasher {
|
|
std::size_t operator()(const boost::shared_ptr<Derivation> &d) const {
|
|
std::size_t seed = 0;
|
|
boost::hash_combine(seed, d->edge.head);
|
|
boost::hash_combine(seed, d->edge.tail);
|
|
boost::hash_combine(seed, d->backPointers);
|
|
return seed;
|
|
}
|
|
};
|
|
|
|
struct DerivationEqualityPred {
|
|
bool operator()(const boost::shared_ptr<Derivation> &d1,
|
|
const boost::shared_ptr<Derivation> &d2) const {
|
|
return d1->edge.head == d2->edge.head &&
|
|
d1->edge.tail == d2->edge.tail &&
|
|
d1->backPointers == d2->backPointers;
|
|
}
|
|
};
|
|
|
|
typedef boost::unordered_set<boost::shared_ptr<Derivation>, DerivationHasher,
|
|
DerivationEqualityPred> DerivationSet;
|
|
|
|
UnweightedHyperarc CreateEdge(const ChartHypothesis &);
|
|
boost::shared_ptr<Vertex> FindOrCreateVertex(const ChartHypothesis &);
|
|
void GetCandidates(Vertex &, std::size_t);
|
|
void LazyKthBest(Vertex &, std::size_t, std::size_t);
|
|
void LazyNext(Vertex &, const Derivation &, std::size_t);
|
|
|
|
VertexMap m_vertexMap;
|
|
DerivationSet m_derivations;
|
|
};
|
|
|
|
} // namespace Moses
|