refine conv

Author: chengduoZH

paddle/operators/conv_op.h

@@ -260,8 +260,11 @@ class GemmConvGradKernel : public framework::OpKernel<T> {
 
  if (input_grad) {
  input_grad->mutable_data<T>(context.GetPlace());
- set_zero(context.device_context(), input_grad, static_cast<T>(0));
-
+ // if is_expand is false, the operation of set_zero is unnecessary,
+ // because math::matmul will reset input_grad.
+ if (is_expand) {
+ set_zero(context.device_context(), input_grad, static_cast<T>(0));
+ }
  math::Col2VolFunctor<Place, T> col2vol;
  math::Col2ImFunctor<math::ColFormat::kCFO, Place, T> col2im;
 

paddle/operators/conv_transpose_op.h

@@ -225,7 +225,7 @@ class GemmConvTransposeGradKernel : public framework::OpKernel<T> {
 
  if (input_grad) {
  input_grad->mutable_data<T>(context.GetPlace());
- set_zero(context.device_context(), input_grad, static_cast<T>(0));
+ // set_zero is unnecessary, math::matmul will reset input_grad.
  }
  if (filter_grad) { // filter size (m, c, k_h, k_w)
  filter_grad->mutable_data<T>(context.GetPlace());