From ea22515ae4ba1b21cc2d10869f8efda19659ce11 Mon Sep 17 00:00:00 2001
From: Zeng Jinle <32832641+sneaxiy@users.noreply.github.com>
Date: Thu, 9 Apr 2020 05:41:02 -0500
Subject: [PATCH] pimpl to polish code, test=develop (#23597)

---
 .../fluid/imperative/partial_grad_engine.cc   | 30 ++++++++-----------
 paddle/fluid/imperative/partial_grad_engine.h | 17 ++++-------
 2 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/paddle/fluid/imperative/partial_grad_engine.cc b/paddle/fluid/imperative/partial_grad_engine.cc
index 135d54d1b7..342d046db7 100644
--- a/paddle/fluid/imperative/partial_grad_engine.cc
+++ b/paddle/fluid/imperative/partial_grad_engine.cc
@@ -1015,34 +1015,28 @@ PartialGradEngine::PartialGradEngine(
     const std::vector<std::shared_ptr<VarBase>> &no_grad_vars,
     const platform::Place &place, const detail::BackwardStrategy &strategy,
     bool create_graph, bool retain_graph, bool allow_unused, bool only_inputs)
-    : input_targets_(input_targets),
-      output_targets_(output_targets),
-      output_grads_(output_grads),
-      no_grad_vars_(no_grad_vars),
-      place_(place),
-      strategy_(strategy),
-      create_graph_(create_graph),
-      retain_graph_(retain_graph),
-      allow_unused_(allow_unused),
-      only_inputs_(only_inputs) {}
+    : task_(new PartialGradTask(input_targets, output_targets, output_grads,
+                                no_grad_vars, place, strategy, create_graph,
+                                retain_graph, allow_unused, only_inputs)) {}
+
+PartialGradEngine::~PartialGradEngine() { Clear(); }
 
 std::vector<std::shared_ptr<VarBase>> PartialGradEngine::GetResult() const {
   return results_;
 }
 
 void PartialGradEngine::Clear() {
-  input_targets_.clear();
-  output_targets_.clear();
-  output_grads_.clear();
-  no_grad_vars_.clear();
+  if (task_) {
+    delete task_;
+    task_ = nullptr;
+  }
 }
 
 void PartialGradEngine::Execute() {
-  PartialGradTask task(input_targets_, output_targets_, output_grads_,
-                       no_grad_vars_, place_, strategy_, create_graph_,
-                       retain_graph_, allow_unused_, only_inputs_);
+  PADDLE_ENFORCE_NOT_NULL(task_, platform::errors::PermissionDenied(
+                                     "PartialGradEngine has been destructed"));
   VLOG(10) << "Starts to execute PartialGradEngine";
-  results_ = task.Run();
+  results_ = task_->Run();
   Clear();
 }
 
diff --git a/paddle/fluid/imperative/partial_grad_engine.h b/paddle/fluid/imperative/partial_grad_engine.h
index 1a0fdcca4f..a7f28c49ec 100644
--- a/paddle/fluid/imperative/partial_grad_engine.h
+++ b/paddle/fluid/imperative/partial_grad_engine.h
@@ -25,6 +25,8 @@ namespace imperative {
 
 class VarBase;
 
+class PartialGradTask;
+
 class PartialGradEngine : public Engine {
  public:
   PartialGradEngine(const std::vector<std::shared_ptr<VarBase>> &input_targets,
@@ -35,6 +37,8 @@ class PartialGradEngine : public Engine {
                     const detail::BackwardStrategy &strategy, bool create_graph,
                     bool retain_graph, bool allow_unused, bool only_inputs);
 
+  ~PartialGradEngine();
+
   void Execute() override;
 
   std::vector<std::shared_ptr<VarBase>> GetResult() const;
@@ -43,17 +47,8 @@ class PartialGradEngine : public Engine {
   void Clear();
 
  private:
-  std::vector<std::shared_ptr<VarBase>> input_targets_;
-  std::vector<std::shared_ptr<VarBase>> output_targets_;
-  std::vector<std::shared_ptr<VarBase>> output_grads_;
-  std::vector<std::shared_ptr<VarBase>> no_grad_vars_;
-  platform::Place place_;
-  detail::BackwardStrategy strategy_;
-  bool create_graph_;
-  bool retain_graph_;
-  bool allow_unused_;
-  bool only_inputs_;
-
+  // Pimpl for fast compilation and stable ABI
+  PartialGradTask *task_{nullptr};
   std::vector<std::shared_ptr<VarBase>> results_;
 };
 
-- 
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