test=develop, fix compile error under gpu mode

paddle/fluid/operators/distributed/parameter_prefetch.h

@@ -47,10 +47,26 @@ void prefetch_with_reconstruct(const std::string& id_name,
   auto* out_value = out.data<T>();
   size_t original_width = original->numel() / original->dims()[0];
 
+  bool is_on_cpu_place = true;
+  if (!platform::is_cpu_place(ids.place())) {
+    is_on_cpu_place = false;
+  }
+
   for (int64_t i = 0; i < ids.numel(); i++) {
     const T* out_rows = out_value + original_width * i;
     T* original_row = original_value + original_width * ids.data<int64_t>()[i];
-    std::memcpy(original_row, out_rows, original_width * sizeof(T));
+    if (is_on_cpu_place) {
+      std::memcpy(original_row, out_rows, original_width * sizeof(T));
+    } else {
+#ifndef PADDLE_WITH_CUDA
+      PADDLE_THROW("paddle is not compiled with CUDA!");
+#else
+      auto stream =
+          static_cast<platform::CUDADeviceContext*>(actual_ctx)->stream();
+      memory::Copy(boost::get<platform::CUDAPlace>(ids.place()), out_rows,
+                   cpu_place, original_row, original_width * sizeof(T), stream);
+#endif
+    }
   }
 }