From 90dc33b5ff53871563a34b1183dedadcf6b2fce1 Mon Sep 17 00:00:00 2001
From: chengduoZH <zhaochengduo@163.com>
Date: Wed, 28 Feb 2018 14:25:20 +0800
Subject: [PATCH] Add todo for reduceSum

---
 paddle/fluid/platform/cuda_helper.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/paddle/fluid/platform/cuda_helper.h b/paddle/fluid/platform/cuda_helper.h
index 029ca609a8..a4ea4f21e3 100644
--- a/paddle/fluid/platform/cuda_helper.h
+++ b/paddle/fluid/platform/cuda_helper.h
@@ -77,6 +77,12 @@ __forceinline__ __device__ T __shfl_down_sync(unsigned, T val, int delta) {
 
 template <typename T>
 __device__ T reduceSum(T val, int tid, int len) {
+  // TODO(zcd): The warp size should be taken from the
+  // parameters of the GPU but not specified as 32 simply.
+  // To make the reduceSum more efficiently,
+  // I use Warp-Level Parallelism and assume the Warp size
+  // is 32 which may be different for different GPU,
+  // but most card's warp size is 32.
   __shared__ T shm[32];
   const int warpSize = 32;
   unsigned mask = 0u;
-- 
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