add checkpoint util class and implement

paddle/fluid/operators/detail/checkpoint.cc

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+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
+#include "paddle/fluid/operators/detail/checkpoint.h"
+
+#include <string>
+
+namespace paddle {
+namespace framework {
+namespace details {
+Checkpoint::Save(const framework::Scope& scope, const platform::Place& place,
+                 const std::string& save_dir, const std::string& var_name,
+                 const bool overwrite) {
+  auto* var = scope.FindVar(var_name);
+  PADDLE_ENFORCE(var != nullptr, "Cannot find variable %s for save_op",
+                 var_name);
+  PADDLE_ENFORCE(var->IsType<framework::LoDTensor>(),
+                 "Checkpoint only supports LoDTensor, %s has wrong type",
+                 var_name);
+
+  bool is_present = FileExists(save_dir);
+  if (is_present && !overwrite) {
+    PADDLE_THROW("%s exists!, checkpoint cannot write  it when overwrite=false",
+                 save_dir, overwrite);
+  }
+
+  MkDirRecursively(DirName(save_dir).c_str());
+  std::ofstream fout(save_dir);
+  PADDLE_ENFORCE(static_cast<bool>(fout), "Cannot open %s to write", save_dir);
+
+  // get device context from pool
+  platform::DeviceContextPool& pool = platform::DeviceContextPool::Instance();
+  auto& dev_ctx = *pool.Get(place);
+
+  auto& tensor = var->Get<framework::LoDTensor>();
+  // Serialize tensor
+  framework::SerializeToStream(fout, tensor, dev_ctx);
+  fout.close();
+}
+}  // namespace details
+}  // namespace framework
+}  // namespace paddle

paddle/fluid/operators/detail/checkpoint.h

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+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
+#include <string>
+
+#include "paddle/fluid/framework/scope.h"
+
+namespace paddle {
+namespace framework {
+namespace details {
+class Checkpoint {
+ public:
+  static void Save(const framework::Scope& scope, const platform::Place& place,
+                   const std::string& save_dir, const std::string& var_name,
+                   const bool overwrite);
+
+  static void Load();
+}
+}  // namespace details
+}  // namespace framework
+}  // namespace paddle