Hello,
I am trying to implement a custom weighted loss based on my labels. I have a regression prediction task, and I found that one value (15.0) is rarely predicted, so I want to have higher loss on that value to force the model to predict it. I looked online and tried to implement this loss, but it isn’t working.
This is what I tried. The given_input comes from the model and target has shape (130, 1, 144):
def weighted_loss(given_input, target):
    curr_loss_list = []
    target_data = torch.squeeze(target.data)
    given_input = torch.squeeze(given_input.data)
    for batch_counter, batch_val in enumerate(target_data):
        for counter, val in enumerate(batch_val):
            # this is the value we want to penalize more severely
            if val == 15.0:
                curr_loss_list.append(((given_input[batch_counter, counter] - val)**2 * 5))
            else:
                curr_loss_list.append((given_input[batch_counter, counter] - val)**2)
    curr_loss = torch.mean(torch.cat(torch.FloatTensor(curr_loss_list), 0))
    return curr_loss


# later on in the training code
optimizer = torch.optim.Adam(model.parameters(), learning_rate)
optimizer.zero_grad()
outs = model(image, question)

if torch.cuda.is_available():
    train_loss = weighted_loss(outs, Variable(label).cuda())
else:
    train_loss = weighted_loss(outs, Variable(label).cpu())

train_loss.backward()
optimizer.step()


The error I am currently getting is:
TypeError: cat received an invalid combination of arguments - got (torch.FloatTensor, int), but expected one of:
 * (sequence[torch.FloatTensor] seq)
 * (sequence[torch.FloatTensor] seq, int dim)
      didn't match because some of the arguments have invalid types: (!torch.FloatTensor!, int)

However, I’m not sure that even if I fix this that this will work and PyTorch will be able to compute the gradients. Is it possible to implement this without writing a custom backward function?
Thanks