FFState *LanguageModelDALM::Evaluate(const Hypothesis &hypo, const FFState *ps, ScoreComponentCollection *out) const{
// In this function, we only compute the LM scores of n-grams that overlap a
// phrase boundary. Phrase-internal scores are taken directly from the
// translation option.
const DALMState *dalm_ps = static_cast<const DALMState *>(ps);
// Empty phrase added? nothing to be done
if (hypo.GetCurrTargetLength() == 0){
return dalm_ps ? new DALMState(*dalm_ps) : NULL;
}
const std::size_t begin = hypo.GetCurrTargetWordsRange().GetStartPos();
//[begin, end) in STL-like fashion.
const std::size_t end = hypo.GetCurrTargetWordsRange().GetEndPos() + 1;
const std::size_t adjust_end = std::min(end, begin + m_nGramOrder - 1);
DALMState *dalm_state = new DALMState(*dalm_ps);
std::size_t position = begin;
float score = 0.0;
for(; position < adjust_end; position++){
score += GetValue(hypo.GetWord(position), dalm_state->get_state()).score;
}
if (hypo.IsSourceCompleted()) {
// Score end of sentence.
std::vector<DALM::VocabId> indices(m_nGramOrder-1);
const DALM::VocabId *last = LastIDs(hypo, &indices.front());
m_lm->set_state(&indices.front(), (last-&indices.front()), *dalm_state->get_state());
float s = GetValue(wid_end, dalm_state->get_state()).score;
score += s;
} else if (adjust_end < end) {
// Get state after adding a long phrase.
std::vector<DALM::VocabId> indices(m_nGramOrder-1);
const DALM::VocabId *last = LastIDs(hypo, &indices.front());
m_lm->set_state(&indices.front(), (last-&indices.front()), *dalm_state->get_state());
}
if (OOVFeatureEnabled()) {
std::vector<float> scores(2);
scores[0] = score;
scores[1] = 0.0;
out->PlusEquals(this, scores);
} else {
out->PlusEquals(this, score);
}
return dalm_state;
}
void KENLM<Model>::EvaluateWhenApplied(const ManagerBase &mgr,
const Hypothesis &hypo, const FFState &prevState, Scores &scores,
FFState &state) const
{
KenLMState &stateCast = static_cast<KenLMState&>(state);
const System &system = mgr.system;
const lm::ngram::State &in_state =
static_cast<const KenLMState&>(prevState).state;
if (!hypo.GetTargetPhrase().GetSize()) {
stateCast.state = in_state;
return;
}
const std::size_t begin = hypo.GetCurrTargetWordsRange().GetStartPos();
//[begin, end) in STL-like fashion.
const std::size_t end = hypo.GetCurrTargetWordsRange().GetEndPos() + 1;
const std::size_t adjust_end = std::min(end, begin + m_ngram->Order() - 1);
std::size_t position = begin;
typename Model::State aux_state;
typename Model::State *state0 = &stateCast.state, *state1 = &aux_state;
float score = m_ngram->Score(in_state, TranslateID(hypo.GetWord(position)),
*state0);
++position;
for (; position < adjust_end; ++position) {
score += m_ngram->Score(*state0, TranslateID(hypo.GetWord(position)),
*state1);
std::swap(state0, state1);
}
if (hypo.GetBitmap().IsComplete()) {
// Score end of sentence.
std::vector<lm::WordIndex> indices(m_ngram->Order() - 1);
const lm::WordIndex *last = LastIDs(hypo, &indices.front());
score += m_ngram->FullScoreForgotState(&indices.front(), last,
m_ngram->GetVocabulary().EndSentence(), stateCast.state).prob;
} else if (adjust_end < end) {
// Get state after adding a long phrase.
std::vector<lm::WordIndex> indices(m_ngram->Order() - 1);
const lm::WordIndex *last = LastIDs(hypo, &indices.front());
m_ngram->GetState(&indices.front(), last, stateCast.state);
} else if (state0 != &stateCast.state) {
// Short enough phrase that we can just reuse the state.
stateCast.state = *state0;
}
score = TransformLMScore(score);
bool OOVFeatureEnabled = false;
if (OOVFeatureEnabled) {
std::vector<float> scoresVec(2);
scoresVec[0] = score;
scoresVec[1] = 0.0;
scores.PlusEquals(system, *this, scoresVec);
} else {
scores.PlusEquals(system, *this, score);
}
}
