remove right-to-left lm support

fairseq/data/token_block_dataset.py

@@ -29,13 +29,12 @@ class TokenBlockDataset(torch.utils.data.Dataset):
         include_targets: return next tokens as targets
     """
 
-    def __init__(self, tokens, sizes, block_size, break_mode=None, include_targets=False, reverse=False):
+    def __init__(self, tokens, sizes, block_size, break_mode=None, include_targets=False):
         super().__init__()
 
         self.tokens = tokens
         self.total_size = len(tokens)
         self.include_targets = include_targets
-        self.reverse = reverse
         self.slice_indices = []
 
         if break_mode is None or break_mode == 'none':
@@ -78,19 +77,9 @@ class TokenBlockDataset(torch.utils.data.Dataset):
     def __getitem__(self, index):
         s, e = self.slice_indices[index]
 
-        if self.reverse:
-            item = torch.LongTensor(np.flip(self.tokens[s:e], 0).copy())
-        else:
         item = torch.LongTensor(self.tokens[s:e])
 
         if self.include_targets:
-            if self.reverse:
-                if s == 0:
-                    target = np.concatenate([self.tokens[-1:], item.numpy()[1:]])
-                else:
-                    target = np.concatenate([self.tokens[s - 1:s], item.numpy()[:-1]])
-                return item, torch.LongTensor(target)
-
             # target is the sentence, for source, rotate item one token to the left (would start with eos)
             if s == 0:
                 source = np.concatenate([self.tokens[-1:], self.tokens[0:e - 1]])

fairseq/tasks/language_modeling.py

@@ -36,13 +36,9 @@ class LanguageModelingTask(FairseqTask):
                             help='max number of tokens per sample for LM dataset')
         parser.add_argument('--raw-text', default=False, action='store_true',
                             help='load raw text dataset')
-        parser.add_argument('--right-to-left', default=False, action='store_true',
-                            help='if set, trains a language model right-to-left (instead of left-to-right)')
 
     def __init__(self, args, dictionary):
         super().__init__(args)
-
-        args.right_to_left = getattr(args, 'right_to_left', False)
         self.dictionary = dictionary
 
     @classmethod
@@ -75,7 +71,7 @@ class LanguageModelingTask(FairseqTask):
             loaded_datasets.append(
                 TokenBlockDataset(
                     tokens, ds.sizes, self.args.tokens_per_sample, self.args.sample_break_mode,
-                    include_targets=True, reverse=self.args.right_to_left,
+                    include_targets=True
                 ))
 
             print('| {} {} {} examples'.format(self.args.data, split_k, len(loaded_datasets[-1])))