diff options
Diffstat (limited to 'dtrain/score.cc')
| -rw-r--r-- | dtrain/score.cc | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/dtrain/score.cc b/dtrain/score.cc index b331dc4f..5c356c0f 100644 --- a/dtrain/score.cc +++ b/dtrain/score.cc @@ -122,12 +122,13 @@ SmoothSingleBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, unsigned j = 1; for (unsigned i = 0; i < M; i++) { if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) break; - sum += ((score_t)counts.clipped_[i]/counts.sum_[i])/pow(2.0, N_-j+1); + sum += ((score_t)counts.clipped_[i]/counts.sum_[i])/pow(2., N_-j+1); j++; } return brevity_penalty(hyp_len, ref_len) * sum; } + /* * approx. bleu * @@ -160,6 +161,38 @@ ApproxBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, return (score_t)glob_src_len_ * score; } +/* + * Linear (Corpus) Bleu + * + * as in "Lattice Minimum Bayes-Risk Decoding + * for Statistical Machine Translation" + * (Tromble et al. '08) + * + */ +score_t +LinearBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, + const unsigned rank, const unsigned /*src_len*/) +{ + unsigned hyp_len = hyp.size(), ref_len = ref.size(); + if (ref_len == 0) return 0.; + unsigned M = N_; + if (ref_len < N_) M = ref_len; + NgramCounts counts(M); + if (hyp_len > 0) + counts = make_ngram_counts(hyp, ref, M); + score_t ret = 0.; + for (unsigned i = 0; i < M; i++) { + if (counts.sum_[i] == 0 || onebest_counts_.sum_[i] == 0) break; + ret += counts.sum_[i]/onebest_counts_.sum_[i]; + } + ret = -(hyp_len/(score_t)onebest_len_) + (1./M) * ret; + if (rank == 0) { + onebest_len_ += hyp_len; + onebest_counts_ += counts; + } + return ret; +} + } // namespace |