# Error executing "Kernel-based training of quantum models with scikit-learn" notebook

**URL:** https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751
**Category:** PennyLane Help
**Created:** [November 30, 2023, 8:40am UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751 "2023-11-30T08:40:54Z")
**Posts on this page:** 5
**Page:** 1

<div class="post-metadata">

### Author: ![Guillermo\_Valverde](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/guillermo_valverde/32/1524_2.png) [@Guillermo\_Valverde](https://discuss.pennylane.ai/u/Guillermo_Valverde)
#### Post date: [November 30, 2023, 8:40am UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751/1 "2023-11-30T08:40:54Z")

</div>

Hello.

I am trying to execute in my server pennylane’s " Kernel-based training of quantum models with scikit-learn" notebook but I obtain the following error:

```python
RuntimeError Traceback (most recent call last)
Cell In[13], line 4
      2 batch_size = 20
      3 steps = 100
----> 4 trained_params, trained_bias, loss_history = quantum_model_train(n_layers, steps, batch_size)
      6 pred_test = quantum_model_predict(X_test, trained_params, trained_bias)
      7 print("accuracy on test set:", accuracy_score(pred_test, y_test))

Cell In[12], line 37, in quantum_model_train(n_layers, steps, batch_size)
     34 loss.backward()
     35 return loss
---> 37 opt.step(closure)
     39 return params_torch, bias_torch, loss_history

File ~\AppData\Local\miniconda3\envs\cuantica\Lib\site-packages\torch\optim\optimizer.py:373, in Optimizer.profile_hook_step.<locals>.wrapper(*args, **kwargs)
    368 else:
    369 raise RuntimeError(
    370 f"{func} must return None or a tuple of (new_args, new_kwargs), but got {result}."
    371 )
--> 373 out = func(*args, **kwargs)
    374 self._optimizer_step_code()
    376 # call optimizer step post hooks

File ~\AppData\Local\miniconda3\envs\cuantica\Lib\site-packages\torch\optim\optimizer.py:76, in _use_grad_for_differentiable.<locals>._use_grad(self, *args, **kwargs)
     74 torch.set_grad_enabled(self.defaults['differentiable'])
     75 torch._dynamo.graph_break()
---> 76 ret = func(self, *args, **kwargs)
     77 finally:
     78 torch._dynamo.graph_break()

File ~\AppData\Local\miniconda3\envs\cuantica\Lib\site-packages\torch\optim\adam.py:143, in Adam.step(self, closure)
    141 if closure is not None:
    142 with torch.enable_grad():
--> 143 loss = closure()
    145 for group in self.param_groups:
    146 params_with_grad = [x]

Cell In[12], line 34, in quantum_model_train.<locals>.closure()
     31 if i % 10 == 0:
     32 print("step", i, ", loss", current_loss)
---> 34 loss.backward()
     35 return loss

File ~\AppData\Local\miniconda3\envs\cuantica\Lib\site-packages\torch\_tensor.py:492, in Tensor.backward(self, gradient, retain_graph, create_graph, inputs)
    482 if has_torch_function_unary(self):
    483 return handle_torch_function(
    484 Tensor.backward,
    485 (self,),
   (...)
    490 inputs=inputs,
    491 )
--> 492 torch.autograd.backward(
    493 self, gradient, retain_graph, create_graph, inputs=inputs
    494 )

File ~\AppData\Local\miniconda3\envs\cuantica\Lib\site-packages\torch\autograd\ __init__.py:251, in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables, inputs)
    246 retain_graph = create_graph
    248 # The reason we repeat the same comment below is that
    249 # some Python versions print out the first line of a multi-line function
    250 # calls in the traceback and some print out the last line
--> 251 Variable._execution_engine.run_backward( # Calls into the C++ engine to run the backward pass
    252 tensors,
    253 grad_tensors_,
    254 retain_graph,
    255 create_graph,
    256 inputs,
    257 allow_unreachable=True,
    258 accumulate_grad=True,
    259 )

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

```

I dont know how to solve it. If someone could help me I would be very pleased.

Thanks.

---

<div class="post-metadata">

### Author: ![isaacdevlugt](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/isaacdevlugt/32/1159_2.png) [@isaacdevlugt](https://discuss.pennylane.ai/u/isaacdevlugt)
#### Post date: [November 30, 2023, 7:30pm UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751/2 "2023-11-30T19:30:26Z")

</div>

Hey @Guillermo_Valverde! Welcome back 🙂

The demo runs perfectly fine for me with up-to-date versions of scikit-learn, PyTorch, and PennyLane. I’m not sure what package versions are on your server, but I bet if you update everything to the latest versions that it will work 👍. If you’re using a virtual environment, you can do this:

```auto
python -m pip install --upgrade pennylane torch scikit-learn

```

One thing to note is that `num_executions` is no longer an attribute, so I had to modify the demo a bit. I’ve already made a PR for that here:

> <https://github.com/PennyLaneAI/qml/pull/992>

Let me know if this helps!

---

<div class="post-metadata">

### Author: ![Guillermo\_Valverde](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/guillermo_valverde/32/1524_2.png) [@Guillermo\_Valverde](https://discuss.pennylane.ai/u/Guillermo_Valverde)
#### Post date: [December 1, 2023, 8:42am UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751/3 "2023-12-01T08:42:24Z")

</div>

Problem solved. Thank you very much Isaac! It is very rewarding to have a forum like this that helps you solve your problems when you encounter difficulties.

---

<div class="post-metadata">

### Author: ![isaacdevlugt](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/isaacdevlugt/32/1159_2.png) [@isaacdevlugt](https://discuss.pennylane.ai/u/isaacdevlugt)
#### Post date: [December 1, 2023, 9:47pm UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751/4 "2023-12-01T21:47:27Z")

</div>

Awesome! Glad I could help 🙂 thank you for the positive feedback, as well! I’m happy our work doesn’t go unnoticed 🤩

---

<div class="post-metadata">

### Author: ![isaacdevlugt](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/isaacdevlugt/32/1159_2.png) [@isaacdevlugt](https://discuss.pennylane.ai/u/isaacdevlugt)
#### Post date: [December 1, 2023, 9:50pm UTC](https://discuss.pennylane.ai/t/error-executing-kernel-based-training-of-quantum-models-with-scikit-learn-notebook/3751/5 "2023-12-01T21:50:47Z")

</div>

By the way, we have a very small survey for [PennyLane v0.33](https://bit.ly/PennyLane-v033-survey), and it would be awesome if you’d give us some feedback and tell us about your needs. Thank you! 😁