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// $Id$
/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2006 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
***********************************************************************/
#include <cassert>
#include <limits>
#include <iostream>
#include <sstream>
#include "NGramNode.h"
#include "LanguageModel.h"
#include "TypeDef.h"
#include "Util.h"
#include "FactorCollection.h"
#include "Phrase.h"
#include "StaticData.h"
using namespace std;
// static variable init
const LmId LanguageModel::UNKNOWN_LM_ID(-1);
LanguageModel::LanguageModel() : m_unknownId(0) {
const_cast<ScoreIndexManager&>(StaticData::Instance()->GetScoreIndexManager()).AddScoreProducer(this);
}
LanguageModel::~LanguageModel() {}
// don't inline virtual funcs...
unsigned int LanguageModel::GetNumScoreComponents() const
{
return 1;
}
const std::string LanguageModel::GetScoreProducerDescription() const
{
std::ostringstream oss;
// what about LMs that are over multiple factors at once, POS + stem, for example?
oss << m_nGramOrder << "-gram LM score, factor-type=" << GetFactorType() << ", file=" << m_filename;
return oss.str();
}
/***
* ngramComponent should be an invalid pointer iff n-best ranking is turned off
*/
void LanguageModel::CalcScore(const Phrase &phrase
, float &fullScore
, float &ngramScore) const
{
fullScore = 0;
ngramScore = 0;
FactorType factorType = GetFactorType();
size_t phraseSize = phrase.GetSize();
vector<const Factor*> contextFactor;
contextFactor.reserve(m_nGramOrder);
#undef CDYER_DEBUG_LMSCORE
#ifdef CDYER_DEBUG_LMSCORE
std::cout<<"LM::CalcScore(" << phrase << "):\n";
#endif
// start of sentence
for (size_t currPos = 0 ; currPos < m_nGramOrder - 1 && currPos < phraseSize ; currPos++)
{
contextFactor.push_back(phrase.GetFactor(currPos, factorType));
#ifdef CDYER_DEBUG_LMSCORE
float score = GetValue(contextFactor);
std::cout << "\t" << currPos << ": " << score << std::endl;
#endif
fullScore += GetValue(contextFactor);
}
if (phraseSize >= m_nGramOrder)
{
contextFactor.push_back(phrase.GetFactor(m_nGramOrder - 1, factorType));
ngramScore = GetValue(contextFactor);
#ifdef CDYER_DEBUG_LMSCORE
std::cout << "\t" << m_nGramOrder-1 << " " << ngramScore << " (first full ngram)" << std::endl;
#endif
}
// main loop
for (size_t currPos = m_nGramOrder; currPos < phraseSize ; currPos++)
{ // used by hypo to speed up lm score calc
for (size_t currNGramOrder = 0 ; currNGramOrder < m_nGramOrder - 1 ; currNGramOrder++)
{
contextFactor[currNGramOrder] = contextFactor[currNGramOrder + 1];
}
contextFactor[m_nGramOrder - 1] = phrase.GetFactor(currPos, factorType);
float partScore = GetValue(contextFactor);
#ifdef CDYER_DEBUG_LMSCORE
std::cout << "\t" << currPos << " " << partScore << " (full ngram)" << std::endl;
#endif
ngramScore += partScore;
}
fullScore += ngramScore;
}
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