fix input_grad not set zero. test=develop

paddle/fluid/operators/temporal_shift_op.cu

@@ -129,6 +129,9 @@ class TemporalShiftGradOpCUDAKernel : public framework::OpKernel<T> {
 
     const T* output_grad_data = output_grad->data<T>();
     T* input_grad_data = input_grad->mutable_data<T>({nt, c, h, w}, ctx.GetPlace());
+    math::SetConstant<platform::CUDADeviceContext, T>()(
+        ctx.template device_context<platform::CUDADeviceContext>(), input_grad,
+        static_cast<T>(0));
 
     int pixelNum = nt * chw;
     int grid_dim = (pixelNum + 512 - 1) / 512;

paddle/fluid/operators/temporal_shift_op.h

@@ -88,6 +88,7 @@ class TemporalShiftGradKernel : public framework::OpKernel<T> {
 
     const T* output_grad_data = output_grad->data<T>();
     T* input_grad_data = input_grad->mutable_data<T>({nt, c, h, w}, ctx.GetPlace());
+    memset(input_grad_data, 0, input_grad->numel() * sizeof(T));
 
     int src_it = 0;
     for (int i = 0; i < output_grad->numel(); i++) {