From edb22c2f0c10bd8e70e3e917a6e2c10a2ab044b3 Mon Sep 17 00:00:00 2001
From: Yu Yang <yuyang18@baidu.com>
Date: Fri, 10 Nov 2017 10:54:21 -0800
Subject: [PATCH] Add Scope::Rename (#5534)

it is useful in gradient phase of an operator with block
---
 paddle/framework/scope.cc        | 18 ++++++++++++++++++
 paddle/framework/scope.h         |  9 ++++++++-
 paddle/operators/recurrent_op.cc | 24 ++++++++----------------
 3 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/paddle/framework/scope.cc b/paddle/framework/scope.cc
index fb2c69105..9428b8a07 100644
--- a/paddle/framework/scope.cc
+++ b/paddle/framework/scope.cc
@@ -98,5 +98,23 @@ void Scope::DeleteScope(Scope* scope) {
   delete scope;
 }
 
+void Scope::Rename(const std::string& origin_name,
+                   const std::string& new_name) const {
+  auto origin_it = vars_.find(origin_name);
+  PADDLE_ENFORCE(origin_it != vars_.end(),
+                 "Cannot find original variable with name %s", origin_name);
+  auto new_it = vars_.find(new_name);
+  PADDLE_ENFORCE(new_it == vars_.end(),
+                 "The variable with name %s is already in the scope", new_name);
+  vars_[new_name] = origin_it->second;
+  vars_.erase(origin_it);
+}
+
+std::string Scope::Rename(const std::string& origin_name) const {
+  auto var_name = string::Sprintf("%p.%d", this, vars_.size());
+  Rename(origin_name, var_name);
+  return var_name;
+}
+
 }  // namespace framework
 }  // namespace paddle
diff --git a/paddle/framework/scope.h b/paddle/framework/scope.h
index fb6609493..c2aafb6ad 100644
--- a/paddle/framework/scope.h
+++ b/paddle/framework/scope.h
@@ -68,11 +68,18 @@ class Scope {
   // enumerate all the variables current contains.
   std::vector<std::string> GetAllNames(bool recursive = false) const;
 
+  // Rename variable to a new name
+  void Rename(const std::string& origin_name,
+              const std::string& new_name) const;
+
+  // Rename variable to a new name and return the new name
+  std::string Rename(const std::string& origin_name) const;
+
  private:
   // Call Scope::NewScope for a sub-scope.
   explicit Scope(Scope const* parent) : parent_(parent) {}
 
-  std::unordered_map<std::string, Variable*> vars_;
+  mutable std::unordered_map<std::string, Variable*> vars_;
   mutable std::list<Scope*> kids_;
   Scope const* parent_{nullptr};
 
diff --git a/paddle/operators/recurrent_op.cc b/paddle/operators/recurrent_op.cc
index b0e87b705..0075ccd24 100644
--- a/paddle/operators/recurrent_op.cc
+++ b/paddle/operators/recurrent_op.cc
@@ -387,8 +387,8 @@ class RecurrentGradOp : public RecurrentBase {
         auto &p_names = Inputs(kParameters);
         PADDLE_ENFORCE_EQ(pg_names.size(), p_names.size());
 
-        for (size_t prog_id = 0; prog_id < pg_names.size(); ++prog_id) {
-          auto inside_grad_name = framework::GradVarName(p_names[prog_id]);
+        for (size_t param_id = 0; param_id < pg_names.size(); ++param_id) {
+          auto inside_grad_name = framework::GradVarName(p_names[param_id]);
 
           // If does not compute gradient of that variable inside rnn, just
           // continue
@@ -406,27 +406,19 @@ class RecurrentGradOp : public RecurrentBase {
             attrs["value"] = 0.0f;
 
             auto zero_op = framework::OpRegistry::CreateOp(
-                "fill_constant", {}, {{"Out", {pg_names[prog_id]}}}, attrs);
+                "fill_constant", {}, {{"Out", {pg_names[param_id]}}}, attrs);
             zero_op->Run(scope, dev_ctx);
           }
 
+          auto new_inside_name = cur_scope.Rename(inside_grad_name);
           // sum gradient
-          auto *outside_var = scope.FindVar(pg_names[prog_id]);
-          PADDLE_ENFORCE(outside_var != nullptr);
-          auto &outside_tensor =
-              *outside_var->GetMutable<framework::LoDTensor>();
-
-          std::string result_var_name;
-          auto *local_result_var = cur_scope.Var(&result_var_name);
-          auto &local_result_tensor =
-              *local_result_var->GetMutable<framework::LoDTensor>();
-
-          local_result_tensor.ShareDataWith(outside_tensor);
 
           auto sum_op = framework::OpRegistry::CreateOp(
-              "sum", {{"X", {result_var_name, inside_grad_name}}},
-              {{"Out", {result_var_name}}}, {});
+              "sum", {{"X", {pg_names[param_id], new_inside_name}}},
+              {{"Out", {pg_names[param_id]}}}, {});
           sum_op->Run(cur_scope, dev_ctx);
+
+          cur_scope.Rename(new_inside_name, inside_grad_name);
         }
       }
       VLOG(5) << "Accumulate Parameter finished ";
-- 
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