From f8c6792aa3ac17135f33c2de01f693ea781e1212 Mon Sep 17 00:00:00 2001
From: Yu Yang <yuyang18@baidu.com>
Date: Tue, 12 Sep 2017 19:44:13 -0700
Subject: [PATCH] Extract DevPtrCast to device_ptr_cast.h

---
 paddle/platform/details/device_ptr_cast.h | 56 +++++++++++++++++++++++
 paddle/platform/transform.h               | 40 +++-------------
 2 files changed, 63 insertions(+), 33 deletions(-)
 create mode 100644 paddle/platform/details/device_ptr_cast.h

diff --git a/paddle/platform/details/device_ptr_cast.h b/paddle/platform/details/device_ptr_cast.h
new file mode 100644
index 000000000..4015491fc
--- /dev/null
+++ b/paddle/platform/details/device_ptr_cast.h
@@ -0,0 +1,56 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#pragma once
+
+#ifndef __NVCC__
+#error device_ptr_cast must be include by .cu file
+#endif
+
+#include <thrust/device_ptr.h>
+
+namespace paddle {
+namespace platform {
+namespace details {
+template <typename T, bool is_ptr>
+struct DevicePtrCast;
+
+template <typename T>
+struct DevicePtrCast<T, true> {
+  using ELEM = typename std::remove_pointer<T>::type;
+  using RTYPE = thrust::device_ptr<ELEM>;
+
+  inline thrust::device_ptr<ELEM> operator()(ELEM* ele) const {
+    return thrust::device_pointer_cast(ele);
+  }
+};
+
+template <typename T>
+struct DevicePtrCast<T, false> {
+  using RTYPE = T;
+  inline RTYPE operator()(RTYPE it) const { return it; }
+};
+
+// Cast T to thrust::device_ptr if T is a pointer.
+// Otherwise, e.g., T is a iterator, return T itself.
+template <typename T>
+auto DevPtrCast(T t) ->
+    typename DevicePtrCast<T, std::is_pointer<T>::value>::RTYPE {
+  DevicePtrCast<T, std::is_pointer<T>::value> cast;
+  return cast(t);
+}
+
+}  // namespace details
+}  // namespace platform
+}  // namespace paddle
diff --git a/paddle/platform/transform.h b/paddle/platform/transform.h
index c80446b45..3ee4acd29 100644
--- a/paddle/platform/transform.h
+++ b/paddle/platform/transform.h
@@ -21,41 +21,12 @@
 #include <algorithm>
 #include <type_traits>
 #ifdef __NVCC__
-#include <thrust/device_ptr.h>
 #include <thrust/transform.h>
+#include "paddle/platform/details/device_ptr_cast.h"
 #endif
 
 namespace paddle {
 namespace platform {
-
-#ifdef __NVCC__
-template <typename T, bool is_ptr>
-struct DevicePtrCast;
-
-template <typename T>
-struct DevicePtrCast<T, true> {
-  using ELEM = typename std::remove_pointer<T>::type;
-  using RTYPE = thrust::device_ptr<ELEM>;
-
-  inline thrust::device_ptr<ELEM> operator()(ELEM* ele) const {
-    return thrust::device_pointer_cast(ele);
-  }
-};
-
-template <typename T>
-struct DevicePtrCast<T, false> {
-  using RTYPE = T;
-  inline RTYPE operator()(RTYPE it) const { return it; }
-};
-
-template <typename T>
-auto DevCast(T t) ->
-    typename DevicePtrCast<T, std::is_pointer<T>::value>::RTYPE {
-  DevicePtrCast<T, std::is_pointer<T>::value> cast;
-  return cast(t);
-}
-#endif
-
 // Transform on host or device. It provides the same API in std library.
 template <typename Place, typename InputIter, typename OutputIter,
           typename UnaryOperation>
@@ -65,7 +36,9 @@ void Transform(Place place, InputIter first, InputIter last, OutputIter result,
     std::transform(first, last, result, op);
   } else {
 #ifdef __NVCC__
-    thrust::transform(DevCast(first), DevCast(last), DevCast(result), op);
+    using namespace details;
+    thrust::transform(DevPtrCast(first), DevPtrCast(last), DevPtrCast(result),
+                      op);
 #else
     PADDLE_THROW("Do not invoke `Transform<GPUPlace>` in .cc file");
 #endif
@@ -80,8 +53,9 @@ void Transform(Place place, InputIter1 first1, InputIter1 last1,
     std::transform(first1, last1, first2, result, op);
   } else {
 #ifdef __NVCC__
-    thrust::transform(DevCast(first1), DevCast(last1), DevCast(first2),
-                      DevCast(result), op);
+    using namespace details;
+    thrust::transform(DevPtrCast(first1), DevPtrCast(last1), DevPtrCast(first2),
+                      DevPtrCast(result), op);
 #else
     PADDLE_THROW("Do not invoke `Transform<GPUPlace>` in .cc file");
 #endif
-- 
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