mirror of
https://github.com/moses-smt/mosesdecoder.git
synced 2025-01-06 19:49:41 +03:00
293 lines
7.8 KiB
C++
293 lines
7.8 KiB
C++
/*
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* KENLM.cpp
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*
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* Created on: 4 Nov 2015
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* Author: hieu
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*/
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#include <sstream>
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#include <vector>
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#include "KENLM.h"
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#include "../TargetPhrase.h"
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#include "../Scores.h"
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#include "../System.h"
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#include "../Search/Hypothesis.h"
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#include "../Search/Manager.h"
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#include "lm/state.hh"
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#include "lm/left.hh"
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#include "../legacy/FactorCollection.h"
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using namespace std;
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namespace Moses2
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{
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struct KenLMState : public FFState {
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lm::ngram::State state;
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virtual size_t hash() const {
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size_t ret = hash_value(state);
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return ret;
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}
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virtual bool operator==(const FFState& o) const {
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const KenLMState &other = static_cast<const KenLMState &>(o);
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bool ret = state == other.state;
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return ret;
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}
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virtual std::string ToString() const
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{
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stringstream ss;
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for (size_t i = 0; i < state.Length(); ++i) {
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ss << state.words[i] << " ";
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}
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return ss.str();
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}
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};
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/////////////////////////////////////////////////////////////////
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class MappingBuilder : public lm::EnumerateVocab
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{
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public:
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MappingBuilder(FactorCollection &factorCollection, System &system, std::vector<lm::WordIndex> &mapping)
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: m_factorCollection(factorCollection)
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, m_system(system)
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, m_mapping(mapping)
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{}
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void Add(lm::WordIndex index, const StringPiece &str) {
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std::size_t factorId = m_factorCollection.AddFactor(str, m_system)->GetId();
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if (m_mapping.size() <= factorId) {
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// 0 is <unk> :-)
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m_mapping.resize(factorId + 1);
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}
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m_mapping[factorId] = index;
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}
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private:
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FactorCollection &m_factorCollection;
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std::vector<lm::WordIndex> &m_mapping;
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System &m_system;
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};
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/////////////////////////////////////////////////////////////////
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KENLM::KENLM(size_t startInd, const std::string &line)
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:StatefulFeatureFunction(startInd, line)
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,m_lazy(false)
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{
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ReadParameters();
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}
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KENLM::~KENLM()
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{
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// TODO Auto-generated destructor stub
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}
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void KENLM::Load(System &system)
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{
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FactorCollection &fc = system.GetVocab();
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m_bos = fc.AddFactor(BOS_, system, false);
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m_eos = fc.AddFactor(EOS_, system, false);
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lm::ngram::Config config;
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config.messages = NULL;
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FactorCollection &collection = system.GetVocab();
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MappingBuilder builder(collection, system, m_lmIdLookup);
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config.enumerate_vocab = &builder;
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config.load_method = m_lazy ? util::LAZY : util::POPULATE_OR_READ;
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m_ngram.reset(new Model(m_path.c_str(), config));
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}
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void KENLM::SetParameter(const std::string& key, const std::string& value)
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{
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if (key == "path") {
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m_path = value;
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}
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else if (key == "factor") {
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m_factorType = Scan<FactorType>(value);
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}
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else if (key == "lazyken") {
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m_lazy = Scan<bool>(value);
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}
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else if (key == "order") {
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// don't need to store it
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}
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else {
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StatefulFeatureFunction::SetParameter(key, value);
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}
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}
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FFState* KENLM::BlankState(MemPool &pool) const
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{
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KenLMState *ret = new (pool.Allocate<KenLMState>()) KenLMState();
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return ret;
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}
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//! return the state associated with the empty hypothesis for a given sentence
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void KENLM::EmptyHypothesisState(FFState &state,
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const Manager &mgr,
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const InputType &input,
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const Hypothesis &hypo) const
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{
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KenLMState &stateCast = static_cast<KenLMState&>(state);
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stateCast.state = m_ngram->BeginSentenceState();
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}
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void
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KENLM::EvaluateInIsolation(MemPool &pool,
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const System &system,
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const Phrase &source,
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const TargetPhrase &targetPhrase,
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Scores &scores,
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SCORE *estimatedScore) const
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{
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// contains factors used by this LM
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float fullScore, nGramScore;
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size_t oovCount;
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CalcScore(targetPhrase, fullScore, nGramScore, oovCount);
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float estimateScore = fullScore - nGramScore;
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bool GetLMEnableOOVFeature = false;
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if (GetLMEnableOOVFeature) {
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float scoresVec[2], estimateScoresVec[2];
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scoresVec[0] = nGramScore;
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scoresVec[1] = oovCount;
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scores.PlusEquals(system, *this, scoresVec);
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estimateScoresVec[0] = estimateScore;
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estimateScoresVec[1] = 0;
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SCORE weightedScore = Scores::CalcWeightedScore(system, *this, estimateScoresVec);
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(*estimatedScore) += weightedScore;
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}
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else {
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scores.PlusEquals(system, *this, nGramScore);
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SCORE weightedScore = Scores::CalcWeightedScore(system, *this, estimateScore);
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(*estimatedScore) += weightedScore;
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}
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}
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void KENLM::EvaluateWhenApplied(const Manager &mgr,
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const Hypothesis &hypo,
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const FFState &prevState,
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Scores &scores,
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FFState &state) const
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{
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KenLMState &stateCast = static_cast<KenLMState&>(state);
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const System &system = mgr.system;
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const lm::ngram::State &in_state = static_cast<const KenLMState&>(prevState).state;
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if (!hypo.GetTargetPhrase().GetSize()) {
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stateCast.state = in_state;
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return;
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}
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const std::size_t begin = hypo.GetCurrTargetWordsRange().GetStartPos();
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//[begin, end) in STL-like fashion.
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const std::size_t end = hypo.GetCurrTargetWordsRange().GetEndPos() + 1;
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const std::size_t adjust_end = std::min(end, begin + m_ngram->Order() - 1);
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std::size_t position = begin;
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typename Model::State aux_state;
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typename Model::State *state0 = &stateCast.state, *state1 = &aux_state;
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float score = m_ngram->Score(in_state, TranslateID(hypo.GetWord(position)), *state0);
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++position;
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for (; position < adjust_end; ++position) {
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score += m_ngram->Score(*state0, TranslateID(hypo.GetWord(position)), *state1);
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std::swap(state0, state1);
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}
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if (hypo.GetBitmap().IsComplete()) {
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// Score end of sentence.
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std::vector<lm::WordIndex> indices(m_ngram->Order() - 1);
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const lm::WordIndex *last = LastIDs(hypo, &indices.front());
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score += m_ngram->FullScoreForgotState(&indices.front(), last, m_ngram->GetVocabulary().EndSentence(), stateCast.state).prob;
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} else if (adjust_end < end) {
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// Get state after adding a long phrase.
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std::vector<lm::WordIndex> indices(m_ngram->Order() - 1);
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const lm::WordIndex *last = LastIDs(hypo, &indices.front());
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m_ngram->GetState(&indices.front(), last, stateCast.state);
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} else if (state0 != &stateCast.state) {
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// Short enough phrase that we can just reuse the state.
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stateCast.state = *state0;
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}
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score = TransformLMScore(score);
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bool OOVFeatureEnabled = false;
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if (OOVFeatureEnabled) {
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std::vector<float> scoresVec(2);
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scoresVec[0] = score;
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scoresVec[1] = 0.0;
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scores.PlusEquals(system, *this, scoresVec);
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} else {
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scores.PlusEquals(system, *this, score);
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}
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}
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void KENLM::CalcScore(const Phrase &phrase, float &fullScore, float &ngramScore, std::size_t &oovCount) const
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{
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fullScore = 0;
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ngramScore = 0;
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oovCount = 0;
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if (!phrase.GetSize()) return;
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lm::ngram::ChartState discarded_sadly;
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lm::ngram::RuleScore<Model> scorer(*m_ngram, discarded_sadly);
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size_t position;
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if (m_bos == phrase[0][m_factorType]) {
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scorer.BeginSentence();
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position = 1;
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} else {
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position = 0;
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}
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size_t ngramBoundary = m_ngram->Order() - 1;
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size_t end_loop = std::min(ngramBoundary, phrase.GetSize());
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for (; position < end_loop; ++position) {
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const Word &word = phrase[position];
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lm::WordIndex index = TranslateID(word);
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scorer.Terminal(index);
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if (!index) ++oovCount;
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}
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float before_boundary = fullScore + scorer.Finish();
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for (; position < phrase.GetSize(); ++position) {
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const Word &word = phrase[position];
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lm::WordIndex index = TranslateID(word);
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scorer.Terminal(index);
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if (!index) ++oovCount;
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}
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fullScore += scorer.Finish();
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ngramScore = TransformLMScore(fullScore - before_boundary);
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fullScore = TransformLMScore(fullScore);
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}
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// Convert last words of hypothesis into vocab ids, returning an end pointer.
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lm::WordIndex *KENLM::LastIDs(const Hypothesis &hypo, lm::WordIndex *indices) const {
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lm::WordIndex *index = indices;
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lm::WordIndex *end = indices + m_ngram->Order() - 1;
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int position = hypo.GetCurrTargetWordsRange().GetEndPos();
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for (; ; ++index, --position) {
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if (index == end) return index;
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if (position == -1) {
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*index = m_ngram->GetVocabulary().BeginSentence();
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return index + 1;
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}
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*index = TranslateID(hypo.GetWord(position));
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}
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}
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}
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