From 8c92f9905ebe7d658087dad9817c167e69f4e401 Mon Sep 17 00:00:00 2001
From: Huilin Qu <huilin.qu@cern.ch>
Date: Mon, 13 Aug 2018 15:51:05 +0200
Subject: [PATCH] Modify MXNet source to avoid rebinding.

---
 .../MXNet/interface/MXNetCppPredictor.h       | 10 +++-------
 PhysicsTools/MXNet/src/MXNetCppPredictor.cc   | 20 ++++++++-----------
 2 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/PhysicsTools/MXNet/interface/MXNetCppPredictor.h b/PhysicsTools/MXNet/interface/MXNetCppPredictor.h
index 140944f921db8..ed97731ac1574 100644
--- a/PhysicsTools/MXNet/interface/MXNetCppPredictor.h
+++ b/PhysicsTools/MXNet/interface/MXNetCppPredictor.h
@@ -54,13 +54,15 @@ class MXNetCppPredictor {
   MXNetCppPredictor(const Block &block, const std::string &output_node);
   virtual ~MXNetCppPredictor();
 
+  // set input array shapes
   void set_input_shapes(const std::vector<std::string>& input_names, const std::vector<std::vector<mx_uint>>& input_shapes);
+
+  // run prediction
   const std::vector<float>& predict(const std::vector<std::vector<mx_float>>& input_data);
 
 private:
   static std::mutex mutex_;
 
-  void infer_shapes();
   void bind_executor();
 
   // context
@@ -78,12 +80,6 @@ class MXNetCppPredictor {
   // names of the input nodes
   std::vector<std::string> input_names_;
 
-  // internal states
-  std::vector<NDArray> arg_arrays;
-  std::vector<NDArray> grad_arrays;
-  std::vector<OpReqType> grad_reqs;
-  std::vector<NDArray> aux_arrays;
-
 };
 
 } /* namespace cpp */
diff --git a/PhysicsTools/MXNet/src/MXNetCppPredictor.cc b/PhysicsTools/MXNet/src/MXNetCppPredictor.cc
index 2511f58f9947c..2ed1bb6b72be6 100644
--- a/PhysicsTools/MXNet/src/MXNetCppPredictor.cc
+++ b/PhysicsTools/MXNet/src/MXNetCppPredictor.cc
@@ -66,16 +66,15 @@ void MXNetCppPredictor::set_input_shapes(const std::vector<std::string>& input_n
     NDArray nd(input_shapes[i], context_, false);
     arg_map_[name] = nd;
   }
-  // infer parameter shapes from input shapes
-  infer_shapes();
 }
 
 const std::vector<float>& MXNetCppPredictor::predict(const std::vector<std::vector<mx_float> >& input_data) {
   assert(input_names_.size() == input_data.size());
 
   try {
-    // bind executor
-    bind_executor();
+    // create the executor (if not done yet)
+    if (!exec_) { bind_executor(); }
+    assert(exec_);
     // set the inputs
     for (unsigned i=0; i<input_names_.size(); ++i){
       const auto& name = input_names_[i];
@@ -91,7 +90,7 @@ const std::vector<float>& MXNetCppPredictor::predict(const std::vector<std::vect
   }
 }
 
-void MXNetCppPredictor::infer_shapes() {
+void MXNetCppPredictor::bind_executor() {
   // acquire lock
   std::lock_guard<std::mutex> lock(mutex_);
 
@@ -109,7 +108,7 @@ void MXNetCppPredictor::infer_shapes() {
   sym_.InferShape(arg_shapes, &in_shapes, &aux_shapes, &out_shapes);
 
   // init argument arrays
-  arg_arrays.clear();
+  std::vector<NDArray> arg_arrays;
   for (size_t i = 0; i < in_shapes.size(); ++i) {
     const auto &shape = in_shapes[i];
     const auto &arg_name = arg_name_list[i];
@@ -120,11 +119,11 @@ void MXNetCppPredictor::infer_shapes() {
       arg_arrays.push_back(NDArray(shape, context_, false));
     }
   }
-  grad_arrays = std::vector<NDArray>(arg_arrays.size());
-  grad_reqs = std::vector<OpReqType>(arg_arrays.size(), kNullOp);
+  std::vector<NDArray> grad_arrays(arg_arrays.size());
+  std::vector<OpReqType> grad_reqs(arg_arrays.size(), kNullOp);
 
   // init auxiliary array
-  aux_arrays.clear();
+  std::vector<NDArray> aux_arrays;
   const auto aux_name_list = sym_.ListAuxiliaryStates();
   for (size_t i = 0; i < aux_shapes.size(); ++i) {
     const auto &shape = aux_shapes[i];
@@ -137,9 +136,6 @@ void MXNetCppPredictor::infer_shapes() {
     }
   }
 
-}
-
-void MXNetCppPredictor::bind_executor() {
   // bind executor
   exec_.reset(new Executor(sym_, context_, arg_arrays, grad_arrays, grad_reqs, aux_arrays));
 }