Add --sentence-bleu option to score.py

Summary: Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/605

Differential Revision: D15518167

Pulled By: myleott

fbshipit-source-id: 8b0e6b32adff018136d0d251b7fde3818e373d6f

score.py

@@ -28,6 +28,8 @@ def get_parser():
                         help='case-insensitive scoring')
     parser.add_argument('--sacrebleu', action='store_true',
                         help='score with sacrebleu')
+    parser.add_argument('--sentence-bleu', action='store_true',
+                        help='report sentence-level BLEUs (i.e., with +1 smoothing)')
     # fmt: on
     return parser
 
@@ -57,6 +59,16 @@ def main():
         def score(fdsys):
             with open(args.ref) as fdref:
                 print(sacrebleu.corpus_bleu(fdsys, [fdref]))
+    elif args.sentence_bleu:
+        def score(fdsys):
+            with open(args.ref) as fdref:
+                scorer = bleu.Scorer(dict.pad(), dict.eos(), dict.unk())
+                for i, (sys_tok, ref_tok) in enumerate(zip(readlines(fdsys), readlines(fdref))):
+                    scorer.reset(one_init=True)
+                    sys_tok = dict.encode_line(sys_tok)
+                    ref_tok = dict.encode_line(ref_tok)
+                    scorer.add(ref_tok, sys_tok)
+                    print(i, scorer.result_string(args.order))
     else:
         def score(fdsys):
             with open(args.ref) as fdref: