It is not None it is a full zero matrix!! And that explains why the weights are not being updated…
But I checked again and this only happens because I use BCELoss AND a softmax activation for the output! With a sigmoid activation, the weights are updated…
Am I doing something wrong? I’m pretty much recreating some other code I had in Keras where I used a categorical cross entropy loss (with one-hot encodings) and a final softmax activation. In pytorch I’m not doing one-hot encodings and I’m using BCELoss.