Refine roi_pool_op to avoid warning

paddle/operators/roi_pool_op.h

@@ -133,54 +133,47 @@ class CPUROIPoolGradOpKernel : public framework::OpKernel<T> {
     auto* in = ctx.Input<framework::Tensor>("X");
     auto* rois = ctx.Input<framework::Tensor>("ROIs");
     auto* argmax = ctx.Input<framework::Tensor>("Argmax");
-
     auto* out_grad =
         ctx.Input<framework::Tensor>(framework::GradVarName("Out"));
-    auto* x_grad =
-        ctx.Output<framework::Tensor>(framework::GradVarName("X"));
+    auto* in_grad = ctx.Output<framework::Tensor>(framework::GradVarName("X"));
 
     auto pooled_height = ctx.Attr<int>("pooled_height");
     auto pooled_width = ctx.Attr<int>("pooled_width");
 
-    if (x_grad) {
-      int channels = in->dims()[1];
-      auto in_stride = framework::stride(in->dims());
-      auto roi_stride = framework::stride(rois->dims());
-
+    if (in_grad) {
       const int64_t* rois_data = rois->data<int64_t>();
-      int rois_num = rois->dims()[0];
-
-      T* x_grad_data = x_grad->mutable_data<T>(ctx.GetPlace());
+      const T* out_grad_data = out_grad->data<T>();
+      const int64_t* argmax_data = argmax->data<int64_t>();
+      T* in_grad_data = in_grad->mutable_data<T>(ctx.GetPlace());
       math::SetConstant<Place, T> set_zero;
-      set_zero(ctx.device_context(), x_grad, static_cast<T>(0));
+      set_zero(ctx.device_context(), in_grad, static_cast<T>(0));
 
-      size_t roi_offset = roi_stride[0];
-      size_t batch_offset = in_stride[0];
-      size_t channel_offset = in_stride[1];
+      auto in_stride = framework::stride(in->dims());
+      auto argmax_stride = framework::stride(argmax->dims());
+      auto roi_stride = framework::stride(rois->dims());
+      auto out_stride = framework::stride(out_grad->dims());
 
-      const T* out_grad_data = out_grad->data<T>();
-      size_t pool_channel_offset = pooled_height * pooled_width;
-      const int64_t* argmax_data = argmax->data<int64_t>();
+      int rois_num = rois->dims()[0];
+      int channels = in->dims()[1];
 
-      for (size_t n = 0; n < rois_num; ++n) {
-        size_t roi_batch_idx = rois_data[0];
-        T* batch_grad_data = x_grad_data + batch_offset * roi_batch_idx;
+      for (int n = 0; n < rois_num; ++n) {
+        int roi_batch_idx = rois_data[0];
+        T* batch_grad_data = in_grad_data + roi_batch_idx * in_stride[0];
         for (int c = 0; c < channels; ++c) {
           for (int ph = 0; ph < pooled_height; ++ph) {
             for (int pw = 0; pw < pooled_width; ++pw) {
-              size_t pool_index = ph * pooled_width + pw;
-
+              int pool_index = ph * pooled_width + pw;
               if (argmax_data[pool_index] >= 0) {
-                size_t index = static_cast<size_t>(argmax_data[pool_index]);
+                auto index = argmax_data[pool_index];
                 batch_grad_data[index] += out_grad_data[pool_index];
               }
             }
           }
-          batch_grad_data += channel_offset;
-          out_grad_data += pool_channel_offset;
-          argmax_data += pool_channel_offset;
+          batch_grad_data += in_stride[1];
+          out_grad_data += out_stride[1];
+          argmax_data += argmax_stride[1];
         }
-        rois_data += roi_offset;
+        rois_data += roi_stride[0];
       }
     }
   }