mirror of
https://github.com/moses-smt/mosesdecoder.git
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144 lines
4.9 KiB
C++
144 lines
4.9 KiB
C++
/***********************************************************************
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Moses - factored phrase-based language decoder
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Copyright (C) 2010 Hieu Hoang
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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***********************************************************************/
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#include <algorithm>
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#include <iostream>
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#include "StaticData.h"
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#include "ChartTranslationOptionList.h"
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#include "ChartTranslationOptions.h"
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#include "ChartCellCollection.h"
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#include "WordsRange.h"
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namespace Moses
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{
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ChartTranslationOptionList::ChartTranslationOptionList(size_t ruleLimit)
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: m_size(0)
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, m_ruleLimit(ruleLimit)
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{
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m_scoreThreshold = std::numeric_limits<float>::infinity();
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}
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ChartTranslationOptionList::~ChartTranslationOptionList()
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{
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RemoveAllInColl(m_collection);
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}
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void ChartTranslationOptionList::Clear()
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{
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m_size = 0;
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m_scoreThreshold = std::numeric_limits<float>::infinity();
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}
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class ChartTranslationOptionOrderer
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{
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public:
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bool operator()(const ChartTranslationOptions* itemA, const ChartTranslationOptions* itemB) const {
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return itemA->GetEstimateOfBestScore() > itemB->GetEstimateOfBestScore();
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}
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};
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void ChartTranslationOptionList::Add(const TargetPhraseCollection &tpc,
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const StackVec &stackVec,
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const WordsRange &range)
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{
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if (tpc.IsEmpty()) {
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return;
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}
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float score = ChartTranslationOptions::CalcEstimateOfBestScore(tpc, stackVec);
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// If the rule limit has already been reached then don't add the option
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// unless it is better than at least one existing option.
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if (m_size > m_ruleLimit && score < m_scoreThreshold) {
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return;
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}
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// Add the option to the list.
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if (m_size == m_collection.size()) {
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// m_collection has reached capacity: create a new object.
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m_collection.push_back(new ChartTranslationOptions(tpc, stackVec,
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range, score));
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} else {
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// Overwrite an unused object.
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*(m_collection[m_size]) = ChartTranslationOptions(tpc, stackVec,
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range, score);
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}
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++m_size;
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// If the rule limit hasn't been exceeded then update the threshold.
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if (m_size <= m_ruleLimit) {
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m_scoreThreshold = (score < m_scoreThreshold) ? score : m_scoreThreshold;
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}
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// Prune if bursting
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if (m_size == m_ruleLimit * 2) {
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std::nth_element(m_collection.begin(),
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m_collection.begin() + m_ruleLimit - 1,
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m_collection.begin() + m_size,
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ChartTranslationOptionOrderer());
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m_scoreThreshold = m_collection[m_ruleLimit-1]->GetEstimateOfBestScore();
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m_size = m_ruleLimit;
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}
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}
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void ChartTranslationOptionList::AddPhraseOOV(TargetPhrase &phrase, std::list<TargetPhraseCollection*> &waste_memory, const WordsRange &range) {
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TargetPhraseCollection *tpc = new TargetPhraseCollection();
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tpc->Add(&phrase);
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waste_memory.push_back(tpc);
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StackVec empty;
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Add(*tpc, empty, range);
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}
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void ChartTranslationOptionList::ApplyThreshold() {
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if (m_size > m_ruleLimit) {
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// Something's gone wrong if the list has grown to m_ruleLimit * 2
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// without being pruned.
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assert(m_size < m_ruleLimit * 2);
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// Reduce the list to the best m_ruleLimit options. The remaining
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// options can be overwritten on subsequent calls to Add().
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std::nth_element(m_collection.begin(),
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m_collection.begin()+m_ruleLimit,
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m_collection.begin()+m_size,
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ChartTranslationOptionOrderer());
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m_size = m_ruleLimit;
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}
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// keep only those over best + threshold
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float scoreThreshold = -std::numeric_limits<float>::infinity();
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CollType::const_iterator iter;
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for (iter = m_collection.begin(); iter != m_collection.begin()+m_size; ++iter) {
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const ChartTranslationOptions *transOpt = *iter;
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float score = transOpt->GetEstimateOfBestScore();
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scoreThreshold = (score > scoreThreshold) ? score : scoreThreshold;
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}
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scoreThreshold += StaticData::Instance().GetTranslationOptionThreshold();
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CollType::iterator bound = std::partition(m_collection.begin(),
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m_collection.begin()+m_size,
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ScoreThresholdPred(scoreThreshold));
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m_size = std::distance(m_collection.begin(), bound);
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}
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}
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