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Floor probability for unknown ngrams in Lattice MBR

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git-svn-id: https://mosesdecoder.svn.sourceforge.net/svnroot/mosesdecoder/trunk@2896 1f5c12ca-751b-0410-a591-d2e778427230
This commit is contained in:
abarun 2010-02-12 18:04:17 +00:00
parent b63de914a5
commit 6aff4f1afd
1 changed files with 25 additions and 14 deletions
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39
moses-cmd/src/LatticeMBR.cpp
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@ -13,7 +13,7 @@
#include <set>
int bleu_order = 4;
float UNKNGRAMLOGPROB = -20;
void GetOutputWords(const TrellisPath &path, vector <Word> &translation){
const std::vector<const Hypothesis *> &edges = path.GetEdges();
@ -297,6 +297,9 @@ void calcNgramPosteriors(Lattice & connectedHyp, map<const Hypothesis*, vector<E
for (map<Phrase, float>::iterator finalScoresIt = finalNgramScores.begin(); finalScoresIt != finalNgramScores.end(); ++finalScoresIt) {
finalScoresIt->second = finalScoresIt->second * scale - Z;
IFVERBOSE(2) {
cout << finalScoresIt->first << " [" << finalScoresIt->second << "]" << endl;
}
}
}
@ -411,18 +414,20 @@ vector<Word> calcMBRSol(const TrellisPathList& nBestList, map<Phrase, float>& f
mbrThetas.push_back(mbrThetas[i-1] / r);
}
}
//cout << "Thetas: ";
// for (size_t i = 0; i < mbrThetas.size(); ++i) {
// cout << mbrThetas[i] << " ";
// }
// cout << endl;
IFVERBOSE(2) {
cout << "Thetas: ";
for (size_t i = 0; i < mbrThetas.size(); ++i) {
cout << mbrThetas[i] << " ";
}
cout << endl;
}
float argmaxScore = -1e20;
TrellisPathList::const_iterator iter;
size_t ctr = 0;
vector<Word> argmaxTranslation;
for (iter = nBestList.begin() ; iter != nBestList.end() ; ++iter)
for (iter = nBestList.begin() ; iter != nBestList.end() ; ++iter, ++ctr)
{
const TrellisPath &path = **iter;
// get words in translation
@ -439,23 +444,29 @@ vector<Word> calcMBRSol(const TrellisPathList& nBestList, map<Phrase, float>& f
float ngramScore = 0;
for (map < Phrase, int >::iterator ngrams = counts.begin(); ngrams != counts.end(); ++ngrams) {
float ngramPosterior = UNKNGRAMLOGPROB;
map<Phrase,float>::const_iterator ngramPosteriorIt = finalNgramScores.find(ngrams->first);
if (ngramPosteriorIt != finalNgramScores.end()) {
ngramPosterior = ngramPosteriorIt->second;
}
if (ngramScore == 0) {
ngramScore = log(ngrams->second) + finalNgramScores[ngrams->first] + log(mbrThetas[(ngrams->first).GetSize()]);
ngramScore = log(ngrams->second) + ngramPosterior + log(mbrThetas[(ngrams->first).GetSize()]);
}
else {
ngramScore = log_sum(ngramScore, float(log(ngrams->second) + finalNgramScores[ngrams->first] + log(mbrThetas[(ngrams->first).GetSize()])));
ngramScore = log_sum(ngramScore, float(log(ngrams->second) + ngramPosterior + log(mbrThetas[(ngrams->first).GetSize()])));
}
//cout << "Ngram: " << ngrams->first << endl;
}
}
mbrScore += exp(ngramScore);
if (mbrScore > argmaxScore){
argmaxScore = mbrScore;
IFVERBOSE(3) {
cout << "NEW BEST: ";
IFVERBOSE(2) {
cout << "HYP " << ctr << "IS NEW BEST: ";
for (int i = 0; i < translation.size(); ++i)
cout << translation[i] << " " ;
cout << translation[i] ;
cout << "[" << argmaxScore << "]" << endl;
}
argmaxTranslation = translation;