The conv2d library was not the problem. I found out problem was listed here 7 : Since I was running VGG on cifar100, I had to rewrite the forward method on pytorch’s default VGG network since its built for ImageNet and includes a averagepool layer that will error with cifar100’s data size. Using types.MethodType to replace methods in a network is incompatible with DataParallel. My solution was to create my own “MyVGG” class that takes a VGG model as an input and takes all of its parameters, and then I could write my own forward function within that class.