ENH: Add cuda.h in platform

paddle/platform/cuda.h

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#pragma once
+
+#ifndef PADDLE_ONLY_CPU
+
+#include <thrust/system/cuda/error.h>
+#include <thrust/system_error.h>
+
+namespace paddle {
+namespace platform {
+
+inline void throw_on_error(cudaError_t e, const char* message) {
+  if (e) {
+    throw thrust::system_error(e, thrust::cuda_category(), message);
+  }
+}
+
+int GetDeviceCount(void) {
+    int count;
+    throw_on_error(cudaGetDeviceCount(&count),
+                   "cudaGetDeviceCount failed");
+    return count;
+}
+
+}  // namespace platform
+}  // namespace paddle
+
+#endif  // PADDLE_ONLY_CPU