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In policy gradient, we have something like this: enter image description here

Is my understanding correct that if I apply log cross-entropy on the last layer, the gradient will be automatically calculated as per formula above?

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  • $\begingroup$ what are inputs of crossentropy? logits and action or logits and target? $\endgroup$ – Kang_Kai Feb 23 at 9:20
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Yes, just take the cross-entropy loss of the last layer and take the gradient with respect to it. The actual action will be the target.

For example, in PyTorch: apply CrossEntropyLoss on the last layer (no need of doing softmax, as it is done implicitly by this function)

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