diff --git a/paddle/fluid/operators/reduce_ops/reduce_op.h b/paddle/fluid/operators/reduce_ops/reduce_op.h
index c43c7e5e76f28..1f852f97728b3 100644
--- a/paddle/fluid/operators/reduce_ops/reduce_op.h
+++ b/paddle/fluid/operators/reduce_ops/reduce_op.h
@@ -562,24 +562,23 @@ class ReduceGradOp : public framework::OperatorWithKernel {
     auto input_data_type = OperatorWithKernel::IndicateVarDataType(
         ctx, framework::GradVarName("Out"));
 
+#ifdef PADDLE_WITH_MKLDNN
     auto CanMKLDNNReduceGradBeUsed = [&]() {
       auto dx_dims = ctx.Input<Tensor>("X")->dims();
       if (ctx.Attr<bool>("reduce_all") ||
-          (ctx.Attr<std::vector<int>>("dim").size() == dx_dims.size()))
+          ((int)ctx.Attr<std::vector<int>>("dim").size() == dx_dims.size()))
         return true;
 
       auto dy_dims = ctx.Input<Tensor>(framework::GradVarName("Out"))->dims();
 
       // Subtensor must be on rightmost part of the bigger tensor
-      for (size_t i = 0; i < dy_dims.size(); ++i) {
+      for (int i = 0; i < dy_dims.size(); ++i) {
         if (dx_dims[dx_dims.size() - dy_dims.size() + i] != dy_dims[i]) {
           return false;
         }
       }
       return true;
     };
-
-#ifdef PADDLE_WITH_MKLDNN
     if (this->CanMKLDNNBeUsed(ctx, input_data_type) &&
         CanMKLDNNReduceGradBeUsed()) {
       return framework::OpKernelType(input_data_type, ctx.GetPlace(),