RuntimeError: The size of tensor a (64) must match the size of tensor b (512) at non-singleton dimension 1

Do I need to reshape my input tensor?
I have tried to reduce my input’s dinmesion:
x = x.permute(0,2,1).mean( dim = [1,2], keepdim = True).squeeze(dim= -1)
however I get
Given groups=1, weight of size [64, 4, 8], expected input[1, 512, 2] to have 4 channels, but got 512 channels instead

Do I need to different loss function ?

Input :

def one_hot_encode(seq):
    """
    Given a DNA sequence, return its one-hot encoding
    """
    # Make sure seq has only allowed bases
    allowed = set("ACTGN")
    if not set(seq).issubset(allowed):
        invalid = set(seq) - allowed
        raise ValueError(f"Sequence contains chars not in allowed DNA alphabet (ACGTN): {invalid}")
    # Dictionary returning one-hot encoding for each nucleotide 
    nuc_d = {'A':[1.0,0.0,0.0,0.0],
             'C':[0.0,1.0,0.0,0.0],
             'G':[0.0,0.0,1.0,0.0],
             'T':[0.0,0.0,0.0,1.0],
             'N':[0.0,0.0,0.0,0.0]
             }
    # Create array from nucleotide sequence
    vec=np.array([nuc_d[x] for x in seq])
    return vec 

class SeqDatasetOHE(Dataset):
    '''
    Dataset for one-hot-encoded sequences
    '''
    def __init__(self,
                 df,
                 seq_col='Seq',
                 target_col= target_col
                ):
        # extract the DNA from the appropriate column in the df
        self.seqs = list(df[seq_col].values)
        self.seq_len = len(self.seqs[0])
        
        # one-hot encode sequences, then stack in a torch tensor
        self.ohe_seqs = torch.stack([torch.tensor(one_hot_encode(x),dtype=torch.float, device=device) for x in self.seqs])
    
        self.labels = torch.tensor(list(df[target_col].values),dtype=torch.float, device=device).unsqueeze(1)
        
    def __len__(self): return len(self.seqs)
    
    def __getitem__(self,idx):
        # Given an index, return a tuple of an X with it's associated Y
        # This is called inside DataLoader
        seq = self.ohe_seqs[idx]
        label = self.labels[idx]
        
        return seq, label

## constructed DataLoaders from Datasets.
def build_dataloaders(train_df,
                      test_df,
                      seq_col='Seq',
                      target_col= target_col,
                      batch_size=batch_size_init,
                      shuffle=True
                     ):
 

    # create Datasets    
    train_ds = SeqDatasetOHE(train_df,seq_col=seq_col,target_col=target_col)
    test_ds = SeqDatasetOHE(test_df,seq_col=seq_col,target_col=target_col)

    # Put DataSets into DataLoaders
    train_dl = DataLoader(train_ds, batch_size=batch_size, shuffle=shuffle)
    test_dl = DataLoader(test_ds, batch_size=batch_size)
    
    #train_dl.ohe_seqs.to("cuda")  # put data into GPU entirely
    #train_dl.labels.to("cuda")
    #test_dl.ohe_seqs.to("cuda")  # put data into GPU entirely
    #test_dl.labels.to("cuda")
    return train_dl,test_dl
    

train_dl, val_dl = build_dataloaders(train_df, val_df)

Model :

# import the necessary packages
from torch.nn import Module,Conv1d,Linear,MaxPool1d,ReLU,Dropout

class model_test(nn.Module): # deepcre model  
    def __init__(self,
                 seq_len: int =1000,
                 kernel_size: int = 8,
                 p = 0.25): # drop out value 
        super().__init__()
        self.seq_len = seq_len
        # adjusting window size corresponding to sequence length 
        window_size = int(seq_len*(8/3000))
        # CNN module
        self.conv11 = Conv1d(4,64,kernel_size=kernel_size, padding='same')
        self.relu11 = ReLU()
        self.conv12 = Conv1d(64,64,kernel_size=kernel_size, padding='same')
        self.relu12 = ReLU()
        self.maxpool1 = MaxPool1d(kernel_size=window_size)
        self.Dropout1 = Dropout(p)
        self.fc1 =Linear(seq_len*p, 1)
    
    def forward(self, x: torch.Tensor):
        """Forward pass."""
        x = x.permute(0,2,1)
        print(x.shape)
        x = self.conv11(x)
        x = self.relu11(x)
        x = self.conv12(x)
        x = self.relu12(x)
        x = self.maxpool1(x)
        x = self.Dropout1(x)
        x = self.fc1(x)
        return x 

Excuting model:

from fastai.optimizer import OptimWrapper
from torch import optim
from functools import partial

# get the sequence length from the first seq in the df
seq_len = len(train_df['Seq'].values[0])
device = 'cuda'

# setting model
model_test = model_test(seq_len)
model_test.to(device)
# setting model to tensor.cuda.double 
model_test.float()

# setting optimizer 
opt = torch.optim.SGD(model_test.parameters(), lr=lr)
opt_func = OptimWrapper(opt=opt)

# Setting learner 
learn = Learner(data, model_test, loss_func=nn.MSELoss(), metrics=accuracy)
learn.opt = OptimWrapper(opt=opt)

Error :

UserWarning: Using a target size (torch.Size([512, 1])) that is different to the input size (torch.Size([512, 64, 1])). This will likely lead to incorrect results due to broadcasting. Please ensure they have the same size.
  return F.mse_loss(input, target, reduction=self.reduction)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[178], line 1
----> 1 learn.fit_one_cycle(n_epoch=1, lr_max=1e-2)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/callback/schedule.py:119, in fit_one_cycle(self, n_epoch, lr_max, div, div_final, pct_start, wd, moms, cbs, reset_opt, start_epoch)
    116 lr_max = np.array([h['lr'] for h in self.opt.hypers])
    117 scheds = {'lr': combined_cos(pct_start, lr_max/div, lr_max, lr_max/div_final),
    118           'mom': combined_cos(pct_start, *(self.moms if moms is None else moms))}
--> 119 self.fit(n_epoch, cbs=ParamScheduler(scheds)+L(cbs), reset_opt=reset_opt, wd=wd, start_epoch=start_epoch)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:264, in Learner.fit(self, n_epoch, lr, wd, cbs, reset_opt, start_epoch)
    262 self.opt.set_hypers(lr=self.lr if lr is None else lr)
    263 self.n_epoch = n_epoch
--> 264 self._with_events(self._do_fit, 'fit', CancelFitException, self._end_cleanup)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:199, in Learner._with_events(self, f, event_type, ex, final)
    198 def _with_events(self, f, event_type, ex, final=noop):
--> 199     try: self(f'before_{event_type}');  f()
    200     except ex: self(f'after_cancel_{event_type}')
    201     self(f'after_{event_type}');  final()

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:253, in Learner._do_fit(self)
    251 for epoch in range(self.n_epoch):
    252     self.epoch=epoch
--> 253     self._with_events(self._do_epoch, 'epoch', CancelEpochException)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:199, in Learner._with_events(self, f, event_type, ex, final)
    198 def _with_events(self, f, event_type, ex, final=noop):
--> 199     try: self(f'before_{event_type}');  f()
    200     except ex: self(f'after_cancel_{event_type}')
    201     self(f'after_{event_type}');  final()

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:247, in Learner._do_epoch(self)
    246 def _do_epoch(self):
--> 247     self._do_epoch_train()
    248     self._do_epoch_validate()

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:239, in Learner._do_epoch_train(self)
    237 def _do_epoch_train(self):
    238     self.dl = self.dls.train
--> 239     self._with_events(self.all_batches, 'train', CancelTrainException)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:199, in Learner._with_events(self, f, event_type, ex, final)
    198 def _with_events(self, f, event_type, ex, final=noop):
--> 199     try: self(f'before_{event_type}');  f()
    200     except ex: self(f'after_cancel_{event_type}')
    201     self(f'after_{event_type}');  final()

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:205, in Learner.all_batches(self)
    203 def all_batches(self):
    204     self.n_iter = len(self.dl)
--> 205     for o in enumerate(self.dl): self.one_batch(*o)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:235, in Learner.one_batch(self, i, b)
    233 b = self._set_device(b)
    234 self._split(b)
--> 235 self._with_events(self._do_one_batch, 'batch', CancelBatchException)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:199, in Learner._with_events(self, f, event_type, ex, final)
    198 def _with_events(self, f, event_type, ex, final=noop):
--> 199     try: self(f'before_{event_type}');  f()
    200     except ex: self(f'after_cancel_{event_type}')
    201     self(f'after_{event_type}');  final()

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/fastai/learner.py:219, in Learner._do_one_batch(self)
    217 self('after_pred')
    218 if len(self.yb):
--> 219     self.loss_grad = self.loss_func(self.pred, *self.yb)
    220     self.loss = self.loss_grad.clone()
    221 self('after_loss')

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/torch/nn/modules/module.py:1501, in Module._call_impl(self, *args, **kwargs)
   1496 # If we don't have any hooks, we want to skip the rest of the logic in
   1497 # this function, and just call forward.
   1498 if not (self._backward_hooks or self._backward_pre_hooks or self._forward_hooks or self._forward_pre_hooks
   1499         or _global_backward_pre_hooks or _global_backward_hooks
   1500         or _global_forward_hooks or _global_forward_pre_hooks):
-> 1501     return forward_call(*args, **kwargs)
   1502 # Do not call functions when jit is used
   1503 full_backward_hooks, non_full_backward_hooks = [], []

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/torch/nn/modules/loss.py:536, in MSELoss.forward(self, input, target)
    535 def forward(self, input: Tensor, target: Tensor) -> Tensor:
--> 536     return F.mse_loss(input, target, reduction=self.reduction)

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/torch/nn/functional.py:3294, in mse_loss(input, target, size_average, reduce, reduction)
   3291 if size_average is not None or reduce is not None:
   3292     reduction = _Reduction.legacy_get_string(size_average, reduce)
-> 3294 expanded_input, expanded_target = torch.broadcast_tensors(input, target)
   3295 return torch._C._nn.mse_loss(expanded_input, expanded_target, _Reduction.get_enum(reduction))

File /mnt/biostat/environments/parkj/dna2rna/lib/python3.11/site-packages/torch/functional.py:74, in broadcast_tensors(*tensors)
     72 if has_torch_function(tensors):
     73     return handle_torch_function(broadcast_tensors, tensors, *tensors)
---> 74 return _VF.broadcast_tensors(tensors)

RuntimeError: The size of tensor a (64) must match the size of tensor b (512) at non-singleton dimension 1