Polish ParallelExectuor constructor into small functions (#32191)

* Refine Constructor logic of ParallelExecutor

* refine function name

* refine code comment

paddle/fluid/framework/parallel_executor.h

@@ -24,6 +24,7 @@ limitations under the License. */
 #include "paddle/fluid/framework/details/build_strategy.h"
 #include "paddle/fluid/framework/details/execution_strategy.h"
 #include "paddle/fluid/framework/details/op_handle_base.h"
+#include "paddle/fluid/framework/details/scope_buffered_ssa_graph_executor.h"
 #include "paddle/fluid/framework/executor.h"
 #include "paddle/fluid/framework/feed_fetch_type.h"
 #include "paddle/fluid/framework/op_info.h"
@@ -41,6 +42,7 @@ namespace framework {
 
 class ParallelExecutorPrivate;
 
+using details::VariableInfo;
 using details::BuildStrategy;
 using details::ExecutionStrategy;
 namespace p = paddle::platform;
@@ -93,6 +95,40 @@ class ParallelExecutor {
                                     const ExecutionStrategy &exec_strategy,
                                     const BuildStrategy &build_strategy) const;
 
+  void InitExecutorPrivateMemberInfo(const ExecutionStrategy &exec_strategy,
+                                     const BuildStrategy &build_strategy,
+                                     size_t device_count,
+                                     const ir::Graph &graph);
+
+  void CreateLocalScopes(Scope *global_scope,
+                         const std::vector<Scope *> &local_scopes,
+                         bool create_new);
+
+  std::unordered_map<Scope *, Scope *> CreateLocalExecScopes(
+      const std::vector<Scope *> &local_scopes, bool create_new);
+
+  std::vector<ir::Graph *> CloneGraphToMultiDevices(ir::Graph *graph);
+
+  void PrepareNCCLCommunicator(Scope *global_scope);
+
+  std::vector<ir::Graph *> CompileGraphWithBuildStrategy(
+      ir::Graph *graph, std::vector<ir::Graph *> *graphs,
+      const std::string &loss_var_name);
+
+  void CreateVariableInfos(std::vector<VariableInfo> *var_infos,
+                           ir::Graph *graph);
+
+  std::vector<ir::Graph *> CreateSSAGraphExecutor(
+      const ExecutionStrategy &exec_strategy,
+      std::vector<ir::Graph *> *async_graphs, ir::Graph *graph);
+
+  void ResetOpHandleScopeMapOfGraphs(
+      const std::vector<ir::Graph *> &final_graphs,
+      const std::unordered_map<Scope *, Scope *> &scope_map);
+
+  void SetReaderOpDeviceInfoOfGraphs(
+      const std::vector<ir::Graph *> &final_graphs);
+
   ParallelExecutorPrivate *member_;
   std::vector<std::unique_ptr<ir::Graph>> async_graphs_;
 };