From 404cc056b8f0de18ee3633c7c6ba28b773320e2e Mon Sep 17 00:00:00 2001
From: dongzhihong <dzhwinter@gmail.com>
Date: Thu, 27 Jul 2017 17:50:17 +0800
Subject: [PATCH] "reverse travesal"

---
 paddle/framework/backward.cc      | 7 +++++--
 paddle/framework/backward_test.cc | 8 ++++----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/paddle/framework/backward.cc b/paddle/framework/backward.cc
index 716e78f342..2d9efdd511 100644
--- a/paddle/framework/backward.cc
+++ b/paddle/framework/backward.cc
@@ -77,14 +77,17 @@ static std::shared_ptr<OperatorBase> BackwardImpl(
   if (forwardOp.IsNetOp()) {
     //! TODO(dzh)
     std::unordered_map<std::string /*var name*/,
-                       std::vector<size_t> /*op offs et*/>
+                       std::vector<size_t> /*op offset*/>
         dup_output_ops;
     size_t local_op_id = 0;
     // Because it is a net op, it can static_cast.
     auto& forwardNet = static_cast<const NetOp&>(forwardOp);
 
     // travesal subnet/op
-    for (auto& fwd : forwardNet.ops_) {
+    for (auto it = forwardNet.ops_.end(); it != forwardNet.ops_.begin(); --it) {
+      auto fwd = *it;
+      // for (auto& fwd : forwardNet.ops_) {
+      // auto bwd = Backward(*fwd, no_grad_names);
       auto bwd = Backward(*fwd, no_grad_names);
       net->AddOp(bwd);
       for (size_t i = 0; i < bwd->outputs_.size(); ++i) {
diff --git a/paddle/framework/backward_test.cc b/paddle/framework/backward_test.cc
index 0666bcc14c..54acc47599 100644
--- a/paddle/framework/backward_test.cc
+++ b/paddle/framework/backward_test.cc
@@ -129,12 +129,12 @@ REGISTER_OP(mul, f::EmptyOp, f::MulOpMaker);
 REGISTER_GRADIENT_OP(mul, mul_grad, f::EmptyOp);
 REGISTER_OP(sigmoid, f::EmptyOp, f::SigmoidOpMaker);
 REGISTER_GRADIENT_OP(sigmoid, sigmoid_grad, f::EmptyOp);
-REGISTER_OP(fc, f::FcOp, f::FcOpMaker);
-REGISTER_OP(many_output_op, f::EmptyOp, f::ManyOutputOpMaker);
-REGISTER_GRADIENT_OP(many_output_op, many_output_op_grad, f::EmptyOp);
 REGISTER_OP(fill_zeros_like, f::EmptyOp, f::FillZeroOpMaker);
 REGISTER_OP(add, f::EmptyOp, f::AddOpMaker);
 REGISTER_GRADIENT_OP(add, add_grad, f::EmptyOp);
+REGISTER_OP(fc, f::FcOp, f::FcOpMaker);
+REGISTER_OP(many_output_op, f::EmptyOp, f::ManyOutputOpMaker);
+REGISTER_GRADIENT_OP(many_output_op, many_output_op_grad, f::EmptyOp);
 
 TEST(Backward, simple_op_grad) {
   auto fwd = f::OpRegistry::CreateOp("rowwise_add", {"X", "b"}, {"Out"}, {});
@@ -218,7 +218,7 @@ TEST(Backward, net_input_of_network_not_need_grad) {
   ASSERT_EQ(2UL, bwd_net->ops_.size());
   ASSERT_TRUE(bwd_net->ops_[1]->IsNetOp());
   auto first_fc_grad = static_cast<f::NetOp *>(bwd_net->ops_[1].get());
-  ASSERT_EQ(3, first_fc_grad->ops_.size());
+  ASSERT_EQ(3UL, first_fc_grad->ops_.size());
   ASSERT_EQ(f::OperatorBase::EMPTY_VAR_NAME(),
             first_fc_grad[2].Output("X" + f::OperatorBase::GRAD_VAR_SUFFIX()));
 }
-- 
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