diff --git a/doc/installation.md b/doc/installation.md
index 412d9fcc4b951b90ade4f26e7225c3f3ee282575..7613387bc46d80791592ff30b9f27308bdf02b1c 100644
--- a/doc/installation.md
+++ b/doc/installation.md
@@ -12,8 +12,8 @@ OpenPose Library - Compilation and Installation
 
 ## Requirements
 - Ubuntu (tested on 14 and 16) or Windows (tested on 10). We do not support any other OS but the community has been able to install it on: CentOS, Windows 7, and Windows 8.
-- GPU with at least 1.5 GB available (the `nvidia-smi` command checks the available GPU memory in Ubuntu).
-- CUDA and cuDNN installed.
+- NVIDIA graphics card with at least 1.5 GB available (the `nvidia-smi` command checks the available GPU memory in Ubuntu).
+- CUDA and cuDNN installed. Note: We found OpenPose working with cuDNN 5.1 ~10% faster than with cuDNN 6.
 - At least 2 GB of free RAM memory.
 - Highly recommended: A CPU with at least 8 cores.
 
diff --git a/include/openpose/core/renderer.hpp b/include/openpose/core/renderer.hpp
index b3d717b138fa04234102997d34d6912791b9d1c2..f06da407ae8d194383b777b395a5f49eafa7b1c1 100644
--- a/include/openpose/core/renderer.hpp
+++ b/include/openpose/core/renderer.hpp
@@ -1,6 +1,7 @@
 #ifndef OPENPOSE_CORE_RENDERER_HPP
 #define OPENPOSE_CORE_RENDERER_HPP
 
+#include <atomic>
 #include <tuple>
 #include <memory> // std::shared_ptr
 #include <openpose/utilities/macros.hpp>