Hi @albanD, thanks for your explanation about the definition of  _convolution_double_backward() 3. When reading this code, I was confused about the parameter like ggI, ggW_r, ggb and gO_r and output_mask and the target of calculating ggW, gI and gW.
Under my superficial understanding of all these, ggW_r means the gradient of convolution kernel? xx_r means a requirement, ggb is the gradient of bias.
Really hope your advice on how to realize these parameters and the calculation of ggW, gI and gW.
Thank you very much!