Add check that --encoder-layers matches --decoder-layers for LSTM (fixes #394)

Summary: Pull Request resolved: https://github.com/pytorch/fairseq/pull/398

Differential Revision: D13358876

Pulled By: myleott

fbshipit-source-id: 57673f2643aac01492cb8f5728bb9f1a34ba6aa7

fairseq/models/fairseq_model.py

@@ -70,6 +70,12 @@ class BaseFairseqModel(nn.Module):
         self.upgrade_state_dict_named(state_dict, '')
 
     def upgrade_state_dict_named(self, state_dict, name):
+        """Upgrade old state dicts to work with newer code.
+
+        Args:
+            state_dict (dict): state dictionary to upgrade, in place
+            name (str): the state dict key corresponding to the current module
+        """
         assert state_dict is not None
 
         def do_upgrade(m, prefix):

fairseq/models/lstm.py

@@ -75,6 +75,9 @@ class LSTMModel(FairseqModel):
         # make sure that all args are properly defaulted (in case there are any new ones)
         base_architecture(args)
 
+        if args.encoder_layers != args.decoder_layers:
+            raise ValueError('--encoder-layers must match --decoder-layers')
+
         def load_pretrained_embedding_from_file(embed_path, dictionary, embed_dim):
             num_embeddings = len(dictionary)
             padding_idx = dictionary.pad()