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/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2010 Hieu Hoang
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
***********************************************************************/
#include <algorithm>
#include <iostream>
#include "StaticData.h"
#include "ChartTranslationOptionList.h"
#include "ChartTranslationOptions.h"
#include "ChartCellCollection.h"
#include "WordsRange.h"
namespace Moses
{
ChartTranslationOptionList::ChartTranslationOptionList(size_t ruleLimit)
: m_size(0)
, m_ruleLimit(ruleLimit)
{
m_scoreThreshold = std::numeric_limits<float>::infinity();
}
ChartTranslationOptionList::~ChartTranslationOptionList()
{
RemoveAllInColl(m_collection);
}
void ChartTranslationOptionList::Clear()
{
m_size = 0;
m_scoreThreshold = std::numeric_limits<float>::infinity();
}
class ChartTranslationOptionOrderer
{
public:
bool operator()(const ChartTranslationOptions* itemA, const ChartTranslationOptions* itemB) const {
return itemA->GetEstimateOfBestScore() > itemB->GetEstimateOfBestScore();
}
};
void ChartTranslationOptionList::Add(const TargetPhraseCollection &tpc,
const StackVec &stackVec,
const WordsRange &range)
{
if (tpc.IsEmpty()) {
return;
}
float score = ChartTranslationOptions::CalcEstimateOfBestScore(tpc, stackVec);
// If the rule limit has already been reached then don't add the option
// unless it is better than at least one existing option.
if (m_size > m_ruleLimit && score < m_scoreThreshold) {
return;
}
// Add the option to the list.
if (m_size == m_collection.size()) {
// m_collection has reached capacity: create a new object.
m_collection.push_back(new ChartTranslationOptions(tpc, stackVec,
range, score));
} else {
// Overwrite an unused object.
*(m_collection[m_size]) = ChartTranslationOptions(tpc, stackVec,
range, score);
}
++m_size;
// If the rule limit hasn't been exceeded then update the threshold.
if (m_size <= m_ruleLimit) {
m_scoreThreshold = (score < m_scoreThreshold) ? score : m_scoreThreshold;
}
// Prune if bursting
if (m_size == m_ruleLimit * 2) {
std::nth_element(m_collection.begin(),
m_collection.begin() + m_ruleLimit - 1,
m_collection.begin() + m_size,
ChartTranslationOptionOrderer());
m_scoreThreshold = m_collection[m_ruleLimit-1]->GetEstimateOfBestScore();
m_size = m_ruleLimit;
}
}
void ChartTranslationOptionList::ShrinkToLimit()
{
if (m_size > m_ruleLimit) {
// Something's gone wrong if the list has grown to m_ruleLimit * 2
// without being pruned.
assert(m_size < m_ruleLimit * 2);
// Reduce the list to the best m_ruleLimit options. The remaining
// options can be overwritten on subsequent calls to Add().
std::nth_element(m_collection.begin(),
m_collection.begin()+m_ruleLimit,
m_collection.begin()+m_size,
ChartTranslationOptionOrderer());
m_size = m_ruleLimit;
}
}
void ChartTranslationOptionList::ApplyThreshold()
{
// keep only those over best + threshold
float scoreThreshold = -std::numeric_limits<float>::infinity();
CollType::const_iterator iter;
for (iter = m_collection.begin(); iter != m_collection.begin()+m_size; ++iter) {
const ChartTranslationOptions *transOpt = *iter;
float score = transOpt->GetEstimateOfBestScore();
scoreThreshold = (score > scoreThreshold) ? score : scoreThreshold;
}
scoreThreshold += StaticData::Instance().GetTranslationOptionThreshold();
CollType::iterator bound = std::partition(m_collection.begin(),
m_collection.begin()+m_size,
ScoreThresholdPred(scoreThreshold));
m_size = std::distance(m_collection.begin(), bound);
}
}
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