Hello, I made a model to predict multiple a real-value quantity, exactly two of them, some values could be negative, but now I need to train the model. Which are loss function and optimizers suited for this? Thanks in advance!

Welcome to the forums!

You have probably noticed that PyTorch can only implicitly create gradients for scalar outputs. Thus, you need to combine them in some way that will make a loss calculation meaningful for your task. A simple objective function like `nn.MSELoss`

might be a good place to start.

You can also take multiple backward passes by specifying `output.backward(retain_graph=True)`

This is a contrived example that you should be able to translate into your problem:

```
x = torch.randn(1, 3, requires_grad=True)
y = torch.randn(3, 2, requires_grad=True)
z = x @ y
z0 = z[:, 0]
z1 = z[:, 1]
z0.backward(retain_graph=True)
z1.backward()
```

Good luck!

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