added best practices for serialization in README and examples

pytorch_pretrained_bert/modeling.py

@@ -32,7 +32,7 @@ import torch
 from torch import nn
 from torch.nn import CrossEntropyLoss
 
-from .file_utils import cached_path
+from .file_utils import cached_path, WEIGHTS_NAME, CONFIG_NAME
 
 logger = logging.getLogger(__name__)
 
@@ -45,8 +45,7 @@ PRETRAINED_MODEL_ARCHIVE_MAP = {
     'bert-base-multilingual-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-multilingual-cased.tar.gz",
     'bert-base-chinese': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-chinese.tar.gz",
 }
-CONFIG_NAME = 'bert_config.json'
-WEIGHTS_NAME = 'pytorch_model.bin'
+BERT_CONFIG_NAME = 'bert_config.json'
 TF_WEIGHTS_NAME = 'model.ckpt'
 
 def load_tf_weights_in_bert(model, tf_checkpoint_path):
@@ -586,6 +585,9 @@ class BertPreTrainedModel(nn.Module):
             serialization_dir = tempdir
         # Load config
         config_file = os.path.join(serialization_dir, CONFIG_NAME)
+        if not os.path.exists(config_file):
+            # Backward compatibility with old naming format
+            config_file = os.path.join(serialization_dir, BERT_CONFIG_NAME)
         config = BertConfig.from_json_file(config_file)
         logger.info("Model config {}".format(config))
         # Instantiate model.