From 1d8fe2a22026e15b009eca8df3c0d0f2fbef3451 Mon Sep 17 00:00:00 2001
From: Yu Yang <yuyang18@baidu.com>
Date: Thu, 22 Mar 2018 08:31:26 +0800
Subject: [PATCH] Enhance device context pool (#9293)

---
 paddle/fluid/platform/device_context.cc | 35 ++++++++++++++-----------
 paddle/fluid/platform/device_context.h  | 18 +++----------
 paddle/fluid/platform/place.h           | 12 +++++++++
 3 files changed, 35 insertions(+), 30 deletions(-)

diff --git a/paddle/fluid/platform/device_context.cc b/paddle/fluid/platform/device_context.cc
index 98b4178177..59b76a1edb 100644
--- a/paddle/fluid/platform/device_context.cc
+++ b/paddle/fluid/platform/device_context.cc
@@ -10,43 +10,45 @@ See the License for the specific language governing permissions and
 limitations under the License. */
 
 #include "paddle/fluid/platform/device_context.h"
+#include <unordered_set>
 #include "paddle/fluid/memory/memory.h"
-
 namespace paddle {
 namespace platform {
 
 DeviceContextPool* DeviceContextPool::pool = nullptr;
 
-const platform::DeviceContext* DeviceContextPool::Get(
-    const platform::Place& place) {
+platform::DeviceContext* DeviceContextPool::Get(const platform::Place& place) {
   auto it = device_contexts_.find(place);
   if (it == device_contexts_.end()) {
     PADDLE_THROW(
         "'Place' is not supported, Please re-compile with WITH_GPU "
         "option");
   }
-  return it->second;
+  return it->second.get();
 }
 
 DeviceContextPool::DeviceContextPool(
     const std::vector<platform::Place>& places) {
   PADDLE_ENFORCE_GT(places.size(), 0);
-  for (size_t i = 0; i < places.size(); i++) {
-    if (platform::is_cpu_place(places[i])) {
+  using PtrType = std::unique_ptr<DeviceContext>;
+  std::unordered_set<Place, PlaceHash> set;
+  for (auto& p : places) {
+    set.insert(p);
+  }
+
+  for (auto& p : set) {
+    if (platform::is_cpu_place(p)) {
 #ifdef PADDLE_WITH_MKLDNN
-      device_contexts_.emplace(places[i],
-                               new platform::MKLDNNDeviceContext(
-                                   boost::get<platform::CPUPlace>(places[i])));
+      device_contexts_.emplace(
+          p, PtrType(new MKLDNNDeviceContext(boost::get<CPUPlace>(p))));
 #else
-      device_contexts_.emplace(places[i],
-                               new platform::CPUDeviceContext(
-                                   boost::get<platform::CPUPlace>(places[i])));
+      device_contexts_.emplace(
+          p, PtrType(new CPUDeviceContext(boost::get<CPUPlace>(p))));
 #endif
-    } else if (platform::is_gpu_place(places[i])) {
+    } else if (platform::is_gpu_place(p)) {
 #ifdef PADDLE_WITH_CUDA
-      device_contexts_.emplace(places[i],
-                               new platform::CUDADeviceContext(
-                                   boost::get<platform::CUDAPlace>(places[i])));
+      device_contexts_.emplace(
+          p, PtrType(new CUDADeviceContext(boost::get<CUDAPlace>(p))));
 #else
       PADDLE_THROW(
           "'CUDAPlace' is not supported, Please re-compile with WITH_GPU "
@@ -159,6 +161,7 @@ CUDADeviceContext::~CUDADeviceContext() {
 Place CUDADeviceContext::GetPlace() const { return place_; }
 
 void CUDADeviceContext::Wait() const {
+  std::lock_guard<std::mutex> guard(mutex_);
   PADDLE_ENFORCE(cudaStreamSynchronize(stream_));
   PADDLE_ENFORCE(cudaGetLastError());
 }
diff --git a/paddle/fluid/platform/device_context.h b/paddle/fluid/platform/device_context.h
index 603b890af1..202394c7be 100644
--- a/paddle/fluid/platform/device_context.h
+++ b/paddle/fluid/platform/device_context.h
@@ -103,6 +103,7 @@ class CUDADeviceContext : public DeviceContext {
   std::unique_ptr<Eigen::GpuDevice> eigen_device_;
   std::unique_ptr<EigenCudaStreamDevice> eigen_stream_;
 
+  mutable std::mutex mutex_;
   cudaStream_t stream_;
   cudnnHandle_t cudnn_handle_;
   cublasHandle_t cublas_handle_;
@@ -159,7 +160,7 @@ class DeviceContextPool {
   }
 
   /*! \brief  Return handle of single device context. */
-  const platform::DeviceContext* Get(const platform::Place& place);
+  platform::DeviceContext* Get(const platform::Place& place);
 
   template <typename Place>
   const typename DefaultDeviceContextType<Place>::TYPE* GetByPlace(
@@ -172,19 +173,8 @@ class DeviceContextPool {
 
  private:
   static DeviceContextPool* pool;
-  constexpr static int LEFT_SHIFT = 8;
-  struct Hash {
-    std::hash<int> hash_;
-    size_t operator()(const platform::Place& place) const {
-      int pre_hash = place.which() << LEFT_SHIFT;
-      if (platform::is_gpu_place(place)) {
-        pre_hash += boost::get<platform::CUDAPlace>(place).GetDeviceId();
-      }
-      return hash_(pre_hash);
-    }
-  };
-  std::unordered_map<const platform::Place, const platform::DeviceContext*,
-                     Hash>
+  std::unordered_map<const platform::Place,
+                     std::unique_ptr<platform::DeviceContext>, PlaceHash>
       device_contexts_;
   DISABLE_COPY_AND_ASSIGN(DeviceContextPool);
 };
diff --git a/paddle/fluid/platform/place.h b/paddle/fluid/platform/place.h
index 501bddfc6e..4cc8b377b8 100644
--- a/paddle/fluid/platform/place.h
+++ b/paddle/fluid/platform/place.h
@@ -65,6 +65,18 @@ bool is_cpu_place(const Place &);
 bool places_are_same_class(const Place &, const Place &);
 bool is_same_place(const Place &, const Place &);
 
+struct PlaceHash {
+  std::size_t operator()(const Place &p) const {
+    constexpr size_t num_dev_bits = 4;
+    std::hash<int> ihash;
+    size_t dev_id = 0;
+    if (is_gpu_place(p)) {
+      dev_id = boost::get<CUDAPlace>(p).device;
+    }
+    return ihash(dev_id << num_dev_bits | p.which());
+  }
+};
+
 std::ostream &operator<<(std::ostream &, const Place &);
 
 template <typename Visitor>
-- 
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