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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 "DecodeStepGeneration.h"
#include "GenerationDictionary.h"
#include "TranslationOption.h"
#include "TranslationOptionCollection.h"
#include "PartialTranslOptColl.h"
#include "FactorCollection.h"
namespace Moses
{
using namespace std;
DecodeStepGeneration::DecodeStepGeneration(GenerationDictionary* dict,
const DecodeStep* prev,
const std::vector<FeatureFunction*> &features)
: DecodeStep(dict, prev, features)
{
}
// helpers
typedef pair<Word, ScoreComponentCollection> WordPair;
typedef list< WordPair > WordList;
// 1st = word
// 2nd = score
typedef list< WordPair >::const_iterator WordListIterator;
/** used in generation: increases iterators when looping through the exponential number of generation expansions */
inline void IncrementIterators(vector< WordListIterator > &wordListIterVector
, const vector< WordList > &wordListVector)
{
for (size_t currPos = 0 ; currPos < wordListVector.size() ; currPos++) {
WordListIterator &iter = wordListIterVector[currPos];
iter++;
if (iter != wordListVector[currPos].end()) {
// eg. 4 -> 5
return;
} else {
// eg 9 -> 10
iter = wordListVector[currPos].begin();
}
}
}
void DecodeStepGeneration::Process(const TranslationOption &inputPartialTranslOpt
, const DecodeStep &decodeStep
, PartialTranslOptColl &outputPartialTranslOptColl
, TranslationOptionCollection * /* toc */
, bool /*adhereTableLimit*/) const
{
if (inputPartialTranslOpt.GetTargetPhrase().GetSize() == 0) {
// word deletion
TranslationOption *newTransOpt = new TranslationOption(inputPartialTranslOpt);
outputPartialTranslOptColl.Add(newTransOpt);
return;
}
// normal generation step
const GenerationDictionary* generationDictionary = decodeStep.GetGenerationDictionaryFeature();
const Phrase &targetPhrase = inputPartialTranslOpt.GetTargetPhrase();
const InputPath &inputPath = inputPartialTranslOpt.GetInputPath();
size_t targetLength = targetPhrase.GetSize();
// generation list for each word in phrase
vector< WordList > wordListVector(targetLength);
// create generation list
int wordListVectorPos = 0;
for (size_t currPos = 0 ; currPos < targetLength ; currPos++) { // going thorugh all words
// generatable factors for this word to be put in wordList
WordList &wordList = wordListVector[wordListVectorPos];
const Word &word = targetPhrase.GetWord(currPos);
// consult dictionary for possible generations for this word
const OutputWordCollection *wordColl = generationDictionary->FindWord(word);
if (wordColl == NULL) {
// word not found in generation dictionary
//toc->ProcessUnknownWord(sourceWordsRange.GetStartPos(), factorCollection);
return; // can't be part of a phrase, special handling
} else {
// sort(*wordColl, CompareWordCollScore);
OutputWordCollection::const_iterator iterWordColl;
for (iterWordColl = wordColl->begin() ; iterWordColl != wordColl->end(); ++iterWordColl) {
const Word &outputWord = (*iterWordColl).first;
const ScoreComponentCollection& score = (*iterWordColl).second;
// enter into word list generated factor(s) and its(their) score(s)
wordList.push_back(WordPair(outputWord, score));
}
wordListVectorPos++; // done, next word
}
}
// use generation list (wordList)
// set up iterators (total number of expansions)
size_t numIteration = 1;
vector< WordListIterator > wordListIterVector(targetLength);
vector< const Word* > mergeWords(targetLength);
for (size_t currPos = 0 ; currPos < targetLength ; currPos++) {
wordListIterVector[currPos] = wordListVector[currPos].begin();
numIteration *= wordListVector[currPos].size();
}
// go thru each possible factor for each word & create hypothesis
for (size_t currIter = 0 ; currIter < numIteration ; currIter++) {
ScoreComponentCollection generationScore; // total score for this string of words
// create vector of words with new factors for last phrase
for (size_t currPos = 0 ; currPos < targetLength ; currPos++) {
const WordPair &wordPair = *wordListIterVector[currPos];
mergeWords[currPos] = &(wordPair.first);
generationScore.PlusEquals(wordPair.second);
}
// merge with existing trans opt
Phrase genPhrase( mergeWords);
if (IsFilteringStep()) {
if (!inputPartialTranslOpt.IsCompatible(genPhrase, m_conflictFactors))
continue;
}
const TargetPhrase &inPhrase = inputPartialTranslOpt.GetTargetPhrase();
TargetPhrase outPhrase(inPhrase);
outPhrase.GetScoreBreakdown().PlusEquals(generationScore);
outPhrase.MergeFactors(genPhrase, m_newOutputFactors);
outPhrase.EvaluateInIsolation(inputPath.GetPhrase(), m_featuresToApply);
const Range &sourceWordsRange = inputPartialTranslOpt.GetSourceWordsRange();
TranslationOption *newTransOpt = new TranslationOption(sourceWordsRange, outPhrase);
assert(newTransOpt);
newTransOpt->SetInputPath(inputPath);
outputPartialTranslOptColl.Add(newTransOpt);
// increment iterators
IncrementIterators(wordListIterVector, wordListVector);
}
}
}
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