Hi,
The problem is that the signature of your forward: forward(ctx, x, height, width, windows, out_channels, weight, bias, n_channels): does not match the order you return the gradients in the backward: return grad_input, grad_weight, grad_bias, None, None, None, None, None. I guess it should be return grad_input, None, None, None, None, grad_weight, grad_bias, None.