From e823ce68bbf7a0f86e2dc45120efa8cc155390d4 Mon Sep 17 00:00:00 2001
From: nhzlx <zlx_hg@163.com>
Date: Wed, 8 Aug 2018 13:26:19 +0000
Subject: [PATCH] filter redundant output

---
 .../inference/analysis/data_flow_graph.cc     | 28 +++++++++++++++++++
 .../inference/analysis/data_flow_graph.h      |  1 +
 .../analysis/data_flow_graph_to_fluid_pass.cc |  1 +
 3 files changed, 30 insertions(+)

diff --git a/paddle/fluid/inference/analysis/data_flow_graph.cc b/paddle/fluid/inference/analysis/data_flow_graph.cc
index 8a3af0a8eb..7f64bc75ae 100644
--- a/paddle/fluid/inference/analysis/data_flow_graph.cc
+++ b/paddle/fluid/inference/analysis/data_flow_graph.cc
@@ -337,6 +337,34 @@ ExtractInputAndOutputOfSubGraph(std::vector<Node *> &graph) {  // NOLINT
                         std::vector<Node *>(outputs.begin(), outputs.end()));
 }
 
+void FilterRedundantOutputOfSubGraph(DataFlowGraph *graph) {
+  std::vector<Node *> op_nodes;
+  for (auto &node : GraphTraits<DataFlowGraph>(graph).nodes_in_TS()) {
+    if (node.type() == Node::Type::kValue || node.deleted()) {
+      continue;
+    }
+    op_nodes.push_back(&node);
+  }
+  size_t op_num = op_nodes.size();
+  for (size_t i = 0; i < op_num; i++) {
+    if (op_nodes[i]->type() == Node::Type::kFunction) continue;
+    std::unordered_set<std::string> follow_up_input_names;
+    for (size_t j = i + 1; j < op_num; j++) {
+      for (auto *in : op_nodes[j]->inlinks) {
+        follow_up_input_names.insert(in->name());
+      }
+    }
+    std::vector<Node *> filtered_subgraph_outlinks;
+    for (auto *out : op_nodes[i]->outlinks) {
+      if (follow_up_input_names.count(out->name())) {
+        filtered_subgraph_outlinks.push_back(out);
+      }
+    }
+    PADDLE_ENFORCE_GE(filtered_subgraph_outlinks.size(), 1UL);
+    op_nodes[i]->outlinks = filtered_subgraph_outlinks;
+  }
+}
+
 }  // namespace analysis
 }  // namespace inference
 }  // namespace paddle
diff --git a/paddle/fluid/inference/analysis/data_flow_graph.h b/paddle/fluid/inference/analysis/data_flow_graph.h
index 16aeae4d35..bb3ec6bbc1 100644
--- a/paddle/fluid/inference/analysis/data_flow_graph.h
+++ b/paddle/fluid/inference/analysis/data_flow_graph.h
@@ -178,6 +178,7 @@ struct GraphTraits<DataFlowGraph> {
 std::pair<std::vector<Node *>, std::vector<Node *>>
 ExtractInputAndOutputOfSubGraph(std::vector<Node *> &graph);  // NOLINT
 
+void FilterRedundantOutputOfSubGraph(DataFlowGraph *graph);
 }  // namespace analysis
 }  // namespace inference
 }  // namespace paddle
diff --git a/paddle/fluid/inference/analysis/data_flow_graph_to_fluid_pass.cc b/paddle/fluid/inference/analysis/data_flow_graph_to_fluid_pass.cc
index 2328d87042..7365c826a8 100644
--- a/paddle/fluid/inference/analysis/data_flow_graph_to_fluid_pass.cc
+++ b/paddle/fluid/inference/analysis/data_flow_graph_to_fluid_pass.cc
@@ -52,6 +52,7 @@ bool DataFlowGraphToFluidPass::Initialize(Argument *argument) {
 bool DataFlowGraphToFluidPass::Finalize() { return true; }
 
 void DataFlowGraphToFluidPass::Run(DataFlowGraph *graph) {
+  FilterRedundantOutputOfSubGraph(graph);
   LOG(INFO) << "graph.inputs " << graph->inputs.size();
   for (auto &node : GraphTraits<DataFlowGraph>(graph).nodes_in_TS()) {
     if (node.deleted()) continue;