diff options
Diffstat (limited to 'training/dtrain/score.cc')
| -rw-r--r-- | training/dtrain/score.cc | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/training/dtrain/score.cc b/training/dtrain/score.cc index 34fc86a9..96d6e10a 100644 --- a/training/dtrain/score.cc +++ b/training/dtrain/score.cc @@ -49,7 +49,7 @@ BleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, * for Machine Translation" * (Lin & Och '04) * - * NOTE: 0 iff no 1gram match + * NOTE: 0 iff no 1gram match ('grounded') */ score_t StupidBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, @@ -74,6 +74,35 @@ StupidBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, } /* + * fixed 'stupid' bleu + * + * as in "Optimizing for Sentence-Level BLEU+1 + * Yields Short Translations" + * (Nakov et al. '12) + */ +score_t +FixedStupidBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref, + const unsigned /*rank*/, const unsigned /*src_len*/) +{ + unsigned hyp_len = hyp.size(), ref_len = ref.size(); + if (hyp_len == 0 || ref_len == 0) return 0.; + NgramCounts counts = make_ngram_counts(hyp, ref, N_); + unsigned M = N_; + vector<score_t> v = w_; + if (ref_len < N_) { + M = ref_len; + for (unsigned i = 0; i < M; i++) v[i] = 1/((score_t)M); + } + score_t sum = 0, add = 0; + for (unsigned i = 0; i < M; i++) { + if (i == 0 && (counts.sum_[i] == 0 || counts.clipped_[i] == 0)) return 0.; + if (i == 1) add = 1; + sum += v[i] * log(((score_t)counts.clipped_[i] + add)/((counts.sum_[i] + add))); + } + return brevity_penalty(hyp_len, ref_len+1) * exp(sum); // <- fix +} + +/* * smooth bleu * * as in "An End-to-End Discriminative Approach |