Update beam search code to support torch.bool change

Summary: Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/797

Differential Revision: D16617067

Pulled By: myleott

fbshipit-source-id: 52e3aeb98d6e3b55ff9154b784028bf13eabfe38

fairseq/search.py

@@ -212,7 +212,7 @@ class Sampling(Search):
 
         # trim the words that are not in top-P by setting their probabilities
         # to 0, so that they would not be sampled later.
-        trim_mask = truncated_mask.bitwise_not()
+        trim_mask = (~truncated_mask)
         trimed_probs = truncated_probs.masked_fill_(trim_mask, 0)
         return trimed_probs, truncated_indices
 

fairseq/sequence_generator.py

@@ -163,7 +163,7 @@ class SequenceGenerator(object):
         # For example, suppose we're sampling and have already finalized 2/5
         # samples. Then the blacklist would mark 2 positions as being ignored,
         # so that we only finalize the remaining 3 samples.
-        blacklist = src_tokens.new(bsz, beam_size).byte().fill_(0)
+        blacklist = src_tokens.new_zeros(bsz, beam_size).eq(-1)  # forward and backward-compatible False mask
 
         # list of completed sentences
         finalized = [[] for i in range(bsz)]