From 17b88811e0087d59a6933921c4d112412f2600e5 Mon Sep 17 00:00:00 2001
From: Xin Pan <panxin.grad@gmail.com>
Date: Sat, 18 Aug 2018 14:42:33 +0800
Subject: [PATCH] fix ProgramToGraph

when while_grad, it writes multiple @EMPTY@ with no VarDesc.
---
 paddle/fluid/framework/ir/graph.cc | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/paddle/fluid/framework/ir/graph.cc b/paddle/fluid/framework/ir/graph.cc
index f87d5212c..55249cf20 100644
--- a/paddle/fluid/framework/ir/graph.cc
+++ b/paddle/fluid/framework/ir/graph.cc
@@ -117,6 +117,15 @@ Graph::Graph(const ProgramDesc &program) : program_(program) {
     }
     // For output args, always create a new var.
     for (auto &each_var_name : op->OutputArgumentNames()) {
+      ir::Node *var = nullptr;
+      if (all_vars.count(each_var_name) != 0) {
+        var = CreateVarNode(all_vars.at(each_var_name));
+      } else {
+        // Operation output vars can be @EMPTY@. For example, while_grad
+        // can have multi @EMPTY@ outputs with no VarDesc.
+        // TODO(panyx0718): Add a test.
+        var = CreateEmptyNode(each_var_name, ir::Node::Type::kVariable);
+      }
       ir::Node *var = CreateVarNode(all_vars.at(each_var_name));
       var_nodes[each_var_name].push_back(var);
       node->outputs.push_back(var);
@@ -208,7 +217,8 @@ Graph::Graph(const ProgramDesc &program) : program_(program) {
       // Add write after write dependence
       ir::Node *upstream_op =
           (*it_old)->inputs.empty() ? nullptr : (*it_old)->inputs[0];
-      if (upstream_op) {
+      // TODO(zcd): Add a test.
+      if (upstream_op && upstream_op != write_op) {
         ir::Node *dep_var = CreateControlDepVar();
         write_op->inputs.push_back(dep_var);
         upstream_op->outputs.push_back(dep_var);
-- 
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