KeyError: 'unexpected key "module.encoder.embedding.weight" in state_dict'
I am getting the following error while trying to load a saved model.

KeyError: 'unexpected key "module.encoder.embedding.weight" in state_dict'

This is the function I am using to load a saved model.

def load_model_states(model, tag):
    """Load a previously saved model states."""
    filename = os.path.join(args.save_path, tag)
    with open(filename, 'rb') as f:
        model.load_state_dict(torch.load(f))


The model is a sequence-to-sequence network whose init function (constructor) is given below.

def __init__(self, dictionary, embedding_index, max_sent_length, args):
    """"Constructor of the class."""
    super(Sequence2Sequence, self).__init__()
    self.dictionary = dictionary
    self.embedding_index = embedding_index
    self.config = args
    self.encoder = Encoder(len(self.dictionary), self.config)
    self.decoder = AttentionDecoder(len(self.dictionary), max_sent_length, self.config)
    self.criterion = nn.NLLLoss()  # Negative log-likelihood loss

    # Initializing the weight parameters for the embedding layer in the encoder.
    self.encoder.init_embedding_weights(self.dictionary, self.embedding_index, self.config.emsize)


When I print the model (sequence-to-sequence network), I get the following.

Sequence2Sequence (
  (encoder): Encoder (
    (drop): Dropout (p = 0.25)
    (embedding): Embedding(43723, 300)
    (rnn): LSTM(300, 300, batch_first=True, dropout=0.25)
  )
  (decoder): AttentionDecoder (
    (embedding): Embedding(43723, 300)
    (attn): Linear (600 -&gt; 12)
    (attn_combine): Linear (600 -&gt; 300)
    (drop): Dropout (p = 0.25)
    (out): Linear (300 -&gt; 43723)
    (rnn): LSTM(300, 300, batch_first=True, dropout=0.25)
  )
  (criterion): NLLLoss (
  )
)


So, module.encoder.embedding is an embedding layer, and module.encoder.embedding.weight represents the associated weight matrix. So, why it says- unexpected key "module.encoder.embedding.weight" in state_dict?

I solved the problem. Actually I was saving the model using nn.DataParallel, which stores the model in module, and then I was trying to load it without DataParallel. So, either I need to add a nn.DataParallel temporarily in my network for loading purposes, or I can load the weights file, create a new ordered dict without the module prefix, and load it back. 

The second workaround looks like the following.

# original saved file with DataParallel
state_dict = torch.load('myfile.pth.tar')
# create new OrderedDict that does not contain `module.`
from collections import OrderedDict
new_state_dict = OrderedDict()
for k, v in state_dict.items():
    name = k[7:] # remove `module.`
    new_state_dict[name] = v
# load params
model.load_state_dict(new_state_dict)


Reference: https://discuss.pytorch.org/t/solved-keyerror-unexpected-key-module-encoder-embedding-weight-in-state-dict/1686
