[RoBERTa] LayerNorm's eps is not a nn.Parameter so there's no point setting it on the model

Instead we correctly store it on the config

(regenerating the hosted config files)

cc @lysandrejik

pytorch_transformers/convert_roberta_checkpoint_to_pytorch.py

@@ -53,6 +53,7 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
         intermediate_size=roberta.args.encoder_ffn_embed_dim,
         max_position_embeddings=514,
         type_vocab_size=1,
+        layer_norm_eps=1e-5, # PyTorch default used in fairseq
     )
     if classification_head:
         config.num_labels = roberta.args.num_classes
@@ -69,7 +70,6 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
     model.roberta.embeddings.token_type_embeddings.weight.data = torch.zeros_like(model.roberta.embeddings.token_type_embeddings.weight)  # just zero them out b/c RoBERTa doesn't use them.
     model.roberta.embeddings.LayerNorm.weight = roberta_sent_encoder.emb_layer_norm.weight
     model.roberta.embeddings.LayerNorm.bias = roberta_sent_encoder.emb_layer_norm.bias
-    model.roberta.embeddings.LayerNorm.variance_epsilon = roberta_sent_encoder.emb_layer_norm.eps
 
     for i in range(config.num_hidden_layers):
         # Encoder: start of layer
@@ -98,7 +98,6 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
         self_output.dense.bias = roberta_layer.self_attn.out_proj.bias
         self_output.LayerNorm.weight = roberta_layer.self_attn_layer_norm.weight
         self_output.LayerNorm.bias = roberta_layer.self_attn_layer_norm.bias
-        self_output.LayerNorm.variance_epsilon = roberta_layer.self_attn_layer_norm.eps
 
         ### intermediate
         intermediate: BertIntermediate = layer.intermediate
@@ -117,7 +116,6 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
         bert_output.dense.bias = roberta_layer.fc2.bias
         bert_output.LayerNorm.weight = roberta_layer.final_layer_norm.weight
         bert_output.LayerNorm.bias = roberta_layer.final_layer_norm.bias
-        bert_output.LayerNorm.variance_epsilon = roberta_layer.final_layer_norm.eps
         #### end of layer
     
     if classification_head:
@@ -131,7 +129,6 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
         model.lm_head.dense.bias = roberta.model.decoder.lm_head.dense.bias
         model.lm_head.layer_norm.weight = roberta.model.decoder.lm_head.layer_norm.weight
         model.lm_head.layer_norm.bias = roberta.model.decoder.lm_head.layer_norm.bias
-        model.lm_head.layer_norm.variance_epsilon = roberta.model.decoder.lm_head.layer_norm.eps
         model.lm_head.decoder.weight = roberta.model.decoder.lm_head.weight
         model.lm_head.bias = roberta.model.decoder.lm_head.bias
 
@@ -144,6 +141,8 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
     else:
         their_output = roberta.model(input_ids)[0]
     print(our_output.shape, their_output.shape)
+    max_absolute_diff = torch.max(torch.abs(our_output - their_output)).item()
+    print(f"max_absolute_diff = {max_absolute_diff}") # ~ 1e-7
     success = torch.allclose(our_output, their_output, atol=1e-3)
     print(
         "Do both models output the same tensors?",