Hi, I am relatively new to building deep learrning models and I seem to be completely confused and stuck with errors related to shape and size.
Here’s the LSTM model and relevant code:
class LSTMTagger(nn.Module):

        def __init__(self):
            super(LSTMTagger, self).__init__()
    #      self.lstm1 = nn.LSTM(input_size = 1, hidden_size = 100)
    #      self.lstm2 = nn.LSTM(100, 50)
            self.embedding = 
    nn.Embedding(wv.vectors.shape[0],512)#embedding_matrix.shape[1])
            self.lstm1 = nn.LSTM(input_size = 512, hidden_size = 64, dropout = 
    0.1,batch_first=True,bidirectional = True)
            self.dropout = nn.Dropout(p = 0.25)
            self.linear1 = nn.Linear(in_features = 128, out_features = 64)
            self.dropout = nn.Dropout(p = 0.25)
            self.linear2 = nn.Linear(in_features = 64, out_features = 1)
            self.sigmoid = nn.Sigmoid()

        def forward(self, X):
            X_embed = self.embedding(X)
            outr1, _ = self.lstm1(X_embed)
            xr = self.dropout(outr1) 
            xr= self.linear1(xr)
            xr = self.dropout(xr)
            xr= self.linear2(xr)
            outr4 = self.sigmoid(xr)
            outr4 = outr4.view(1,-1)

            return outr4

model = LSTMTagger()
torch.multiprocessing.set_sharing_strategy('file_system')
if torch.cuda.device_count() > 1:
  print("Using ", torch.cuda.device_count(), " GPUs")
  # dim = 0 [30, xxx] -> [10, ...], [10, ...], [10, ...] on 3 GPUs

# model =model.load_state_dict(torch.load('best_model_state.bin'))
model = nn.DataParallel(model, device_ids=[0]) #py r
torch.cuda.empty_cache()
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

model = model.to(device)

def train_epoch(
      model,
      data_loader,
      loss_fn,
      optimizer,
      device,
      scheduler,
      n_examples
    ):
      model = model.train()
      losses = []
      correct_predictions = 0
      for d in data_loader:
        print(f"Input ids: {np.shape(d['input_ids'])}\n len: {len(d['input_ids'][0])}")
        input_ids = d["input_ids"].to(device)
        targets = d["targets"].to(device)
        outputs = model(input_ids)
        _, preds = torch.max(outputs, dim=1)
        print(f"outputs is {np.shape(outputs)}")
        print(f"targets is {targets}")
        # continue
        loss = criterion(outputs.squeeze(), targets)
        # loss.backward()
        # nn.utils.clip_grad_norm_(model.parameters(), clip)
        # optimizer.step()
        # loss = loss_fn(outputs, targets)
        correct_predictions += torch.sum(preds == targets)
        losses.append(loss.item())
        loss.backward()
        nn.utils.clip_grad_norm_(model.parameters(), max_norm=1.0)
        optimizer.step()
        scheduler.step()
        optimizer.zero_grad()
      return correct_predictions.double() / n_examples, np.mean(losses)
EPOCHS = 6
optimizer = optim.Adam(model.parameters(), lr=2e-5)
total_steps = len(data_train) * EPOCHS
scheduler = torch.optim.lr_scheduler.StepLR(optimizer, step_size=1)
loss_fn = nn.CrossEntropyLoss().to(device)
history = defaultdict(list)
best_accuracy = 0
criterion = nn.BCELoss()


# In[86]:


print('starting training')
# exit()

for epoch in range(EPOCHS):
#   y_ip= input('Please enter y_ip y_ip value')
  # print()
#   if y_ip=='b':
#     break
      print(f'Epoch {epoch + 1}/{EPOCHS}')
      print('-' * 10)
      train_acc, train_loss = train_epoch(
        model,
        data_train,
        loss_fn,
        optimizer,
        device,
        scheduler,
        len(df_train)
      )


In this instance the sample input is a tensor of size: torch.Size([1, 512])
, that looks like this:
 tensor([[44561,   972,  7891,    94,  2191,   131,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0,     0,     0,     0,     0,     0,     0,     0,     0,
             0,     0]], device='cuda:0')

and output label (targets from train_epoch function) in case is just a simple 1 or 0 label in tensor form such as:
tensor([1], device='cuda:0')

I have been facing issues consistently with this approach. Initially the output was 1x512x1. So, I added

        outr4 = outr4.view(1,-1)

after the sigmoid layer. Then, the output shape was reduced to 1x512 and I used squeeze function but, still, I face errors such as this one:
ValueError: Using a target size (torch.Size([1])) that is different to the input size (torch.Size([512])) is deprecated. Please ensure they have the same size.

I have spent a lot of time trying to figure out what was going on but to no avail. Isn’t the output supposed to be either 1 or 0, instead of being a 1x512 shaped tensor?
I am relatively new to building models, so please excuse my lack of knowledge.