Pytorch BCELoss not accepting lists
My convLSTM model returns a list of hidden states (17 total, size (1,3,128,128)) and my target is a list of 17 images( all tensors size: (3,128,128) 
When the loss function is called, I get the following error:


  File "/Users/xyz/opt/anaconda3/envs/matrix/lib/python3.7/site->packages/torch/nn/modules/loss.py", line 498, in forward
    return F.binary_cross_entropy(input, target, weight=self.weight, >reduction=self.reduction)
  File "/Users/xyz/opt/anaconda3/envs/matrix/lib/python3.7/site->packages/torch/nn/functional.py", line 2052, in binary_cross_entropy
     if target.size() != input.size():
  AttributeError: 'list' object has no attribute 'size'


Part of the training loop:

    hc = model.init_hidden(batch_size=1)
    for batch_idx, (data, target) in enumerate(train_loader):
        optimizer.zero_grad()
        # Set target, images 2 to 18
        target = data[1:]
        if gpu:
            data = data.cuda()
            target = target.cuda()
            hc.cuda()
        # Get outputs of LSTM
        output = model(data, hc)
        # Calculate loss
        loss = criterion(output, target)
        loss.backward()
        optimizer.step()


I was expecting a size mismatch error but got this instead. How can I fix this?

Hi I solved it by using torch.stack. Could have used torch.cat but wanted a tensor with a list of tensors to pass to the loss function to match the target format so used torch.stack. 
