Cannot use lora for a pre-trained model

[HelloWorldLTY]

Hi, I tried to replace our model's linear layer with lora.linear. However, it seems that all of the components in this module cannot be used for finetuning.

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[17], line 26
     17 valid_loader = prepare_dataloader(
     18     valid_data_pt,
     19     batch_size=config.batch_size,
   (...)
     22     drop_last=False,
     23 )
     25 if config.do_train:
---> 26     train(
     27         model,
     28         loader=train_loader,
     29     )
     30 val_loss, val_mre = evaluate(
     31     model,
     32     loader=valid_loader,
     33 )
     34 elapsed = time.time() - epoch_start_time

Cell In[16], line 74, in train(model, loader)
     71     metrics_to_log.update({"train/dab": loss_dab.item()})
     73 model.zero_grad()
---> 74 scaler.scale(loss).backward()
     75 scaler.unscale_(optimizer)
     76 with warnings.catch_warnings(record=True) as w:

File /notebooks/lib/python3.9/site-packages/torch/_tensor.py:487, in Tensor.backward(self, gradient, retain_graph, create_graph, inputs)
    477 if has_torch_function_unary(self):
    478     return handle_torch_function(
    479         Tensor.backward,
    480         (self,),
   (...)
    485         inputs=inputs,
    486     )
--> 487 torch.autograd.backward(
    488     self, gradient, retain_graph, create_graph, inputs=inputs
    489 )

File /notebooks/lib/python3.9/site-packages/torch/autograd/__init__.py:197, in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables, inputs)
    192     retain_graph = create_graph
    194 # The reason we repeat same the comment below is that
    195 # some Python versions print out the first line of a multi-line function
    196 # calls in the traceback and some print out the last line
--> 197 Variable._execution_engine.run_backward(  # Calls into the C++ engine to run the backward pass
    198     tensors, grad_tensors_, retain_graph, create_graph, inputs,
    199     allow_unreachable=True, accumulate_grad=True)

RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn

How to address this problem? Thanks a lot.

[iopwsy]

I have the same problem, but I fix it.
It seems you need set loss.requires_grad = True and it seems normal.
However, the results is not as good. I don't know why.
Maybe the loss here is for basic model rather than LoRA?

[HelloWorldLTY]

Hi, thanks for your exaplaniation. I use another approch to address it.

But my training time is longer.

After using LoRA, it is:

No Lora, it is:

I have no ideas.