From 2bfc7957dada57c1eb8491e04dac70d16b4369ac Mon Sep 17 00:00:00 2001
From: "A. Unique TensorFlower" <gardener@tensorflow.org>
Date: Fri, 6 Jul 2018 14:50:08 -0700
Subject: Make multithreaded conv respect setNumThreads()

PiperOrigin-RevId: 203527657
---
 tensorflow/contrib/lite/kernels/eigen_support.cc | 54 +++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

(limited to 'tensorflow/contrib/lite/kernels/eigen_support.cc')

diff --git a/tensorflow/contrib/lite/kernels/eigen_support.cc b/tensorflow/contrib/lite/kernels/eigen_support.cc
index 94927cb53d..4f0d020793 100644
--- a/tensorflow/contrib/lite/kernels/eigen_support.cc
+++ b/tensorflow/contrib/lite/kernels/eigen_support.cc
@@ -14,14 +14,38 @@ limitations under the License.
 ==============================================================================*/
 #include "tensorflow/contrib/lite/kernels/eigen_support.h"
 
-#include "third_party/eigen3/Eigen/Core"
+#include <utility>
+
+#include "tensorflow/contrib/lite/kernels/internal/optimized/eigen_spatial_convolutions.h"
 #include "tensorflow/contrib/lite/kernels/op_macros.h"
 
 namespace tflite {
 namespace eigen_support {
 namespace {
 
+// We have a single global threadpool for all convolution operations. This means
+// that inferences started from different threads may block each other, but
+// since the underlying resource of CPU cores should be consumed by the
+// operations anyway, it shouldn't affect overall performance.
+class EigenThreadPoolWrapper : public Eigen::ThreadPoolInterface {
+ public:
+  // Takes ownership of 'pool'
+  explicit EigenThreadPoolWrapper(Eigen::ThreadPool* pool) : pool_(pool) {}
+  ~EigenThreadPoolWrapper() override {}
+
+  void Schedule(std::function<void()> fn) override {
+    pool_->Schedule(std::move(fn));
+  }
+  int NumThreads() const override { return pool_->NumThreads(); }
+  int CurrentThreadId() const override { return pool_->CurrentThreadId(); }
+
+ private:
+  std::unique_ptr<Eigen::ThreadPool> pool_;
+};
+
 struct RefCountedEigenContext : public TfLiteExternalContext {
+  std::unique_ptr<Eigen::ThreadPoolInterface> thread_pool_wrapper;
+  std::unique_ptr<Eigen::ThreadPoolDevice> device;
   int num_references = 0;
 };
 
@@ -30,8 +54,26 @@ RefCountedEigenContext* GetEigenContext(TfLiteContext* context) {
       context->GetExternalContext(context, kTfLiteEigenContext));
 }
 
+void InitDevice(TfLiteContext* context, RefCountedEigenContext* ptr) {
+  int num_threads = 4;
+  if (context->recommended_num_threads != -1) {
+    num_threads = context->recommended_num_threads;
+  }
+  ptr->device.reset();  // destroy before we invalidate the thread pool
+  ptr->thread_pool_wrapper.reset(
+      new EigenThreadPoolWrapper(new Eigen::ThreadPool(num_threads)));
+  ptr->device.reset(
+      new Eigen::ThreadPoolDevice(ptr->thread_pool_wrapper.get(), num_threads));
+}
+
 TfLiteStatus Refresh(TfLiteContext* context) {
   Eigen::setNbThreads(context->recommended_num_threads);
+
+  auto* ptr = GetEigenContext(context);
+  if (ptr != nullptr) {
+    InitDevice(context, ptr);
+  }
+
   return kTfLiteOk;
 }
 
@@ -47,6 +89,7 @@ void IncrementUsageCounter(TfLiteContext* context) {
     ptr->type = kTfLiteEigenContext;
     ptr->Refresh = Refresh;
     ptr->num_references = 0;
+    InitDevice(context, ptr);
     context->SetExternalContext(context, kTfLiteEigenContext, ptr);
   }
   ptr->num_references++;
@@ -65,5 +108,14 @@ void DecrementUsageCounter(TfLiteContext* context) {
   }
 }
 
+const Eigen::ThreadPoolDevice* GetThreadPoolDevice(TfLiteContext* context) {
+  auto* ptr = GetEigenContext(context);
+  if (ptr == nullptr) {
+    TF_LITE_FATAL(
+        "Call to GetFromContext() not preceded by IncrementUsageCounter()");
+  }
+  return ptr->device.get();
+}
+
 }  // namespace eigen_support
 }  // namespace tflite
-- 
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