simplify mac mkldnn build (apache#12724)

* remove guard that prevent omp flag in mac

* udpate doc for mac make build

* update docs

* update readme

* set opencv to 1 in instructions

* remove disable opencv line

* update mac docs

* fix indent

MKLDNN_README.md

@@ -45,7 +45,7 @@ If you don't have full [MKL](https://software.intel.com/en-us/intel-mkl) library
 Install the dependencies, required for MXNet, with the following commands:
 
 - [Homebrew](https://brew.sh/)
-- gcc (clang in macOS does not support OpenMP)
+- llvm (clang in macOS does not support OpenMP)
 - OpenCV (for computer vision operations)
 
 ```
@@ -59,8 +59,7 @@ brew install graphviz
 brew tap homebrew/core
 brew install opencv
 brew tap homebrew/versions
-brew install gcc49
-brew link gcc49 #gcc-5 and gcc-7 also work
+brew install llvm
 ```
 
 ### Clone MXNet sources
@@ -70,28 +69,12 @@ git clone --recursive https://github.com/apache/incubator-mxnet.git
 cd incubator-mxnet
 ```
 
-### Enable OpenMP for MacOS
-
-If you want to enable OpenMP for better performance, you should modify the Makefile in MXNet root dictionary:
-
-Add CFLAGS '-fopenmp' for Darwin.
-
-```
-ifeq ($(USE_OPENMP), 1)
-# ifneq ($(UNAME_S), Darwin)
-    CFLAGS += -fopenmp
-# endif
-endif
-```
-
 ### Build MXNet with MKL-DNN
 
 ```
-make -j $(sysctl -n hw.ncpu) CC=gcc-4.9 CXX=g++-4.9 USE_OPENCV=0 USE_OPENMP=1 USE_MKLDNN=1 USE_BLAS=apple USE_PROFILER=1
+LIBRARY_PATH=$(brew --prefix llvm)/lib/ make -j $(sysctl -n hw.ncpu) CC=$(brew --prefix llvm)/bin/clang++ CXX=$(brew --prefix llvm)/bin/clang++ USE_OPENCV=1 USE_OPENMP=1 USE_MKLDNN=1 USE_BLAS=apple USE_PROFILER=1
 ```
 
-*Note: Temporarily disable OPENCV.*
-
 <h2 id="3">Windows</h2>
 
 We recommend to build and install MXNet yourself using [Microsoft Visual Studio 2015](https://www.visualstudio.com/vs/older-downloads/), or you can also try experimentally the latest [Microsoft Visual Studio 2017](https://www.visualstudio.com/downloads/).

Makefile

@@ -145,9 +145,7 @@ else
 endif
 
 ifeq ($(USE_OPENMP), 1)
-	ifneq ($(UNAME_S), Darwin)
-		CFLAGS += -fopenmp
-	endif
+	CFLAGS += -fopenmp
 endif
 
 ifeq ($(USE_NNPACK), 1)

docs/install/osx_setup.md

@@ -65,6 +65,10 @@ Install the dependencies, required for MXNet, with the following commands:
 	brew install openblas
 	brew tap homebrew/core
 	brew install opencv
+
+	# If building with MKLDNN
+	brew install llvm
+
 	# Get pip
 	easy_install pip
 	# For visualization of network graphs
@@ -89,12 +93,18 @@ The file called ```osx.mk``` has the configuration required for building MXNet o
     make -j$(sysctl -n hw.ncpu)
 ```
 
+To build with MKLDNN
+
+```bash
+LIBRARY_PATH=$(brew --prefix llvm)/lib/ make -j $(sysctl -n hw.ncpu) CC=$(brew --prefix llvm)/bin/clang++ CXX=$(brew --prefix llvm)/bin/clang++ USE_OPENCV=1 USE_OPENMP=1 USE_MKLDNN=1 USE_BLAS=apple USE_PROFILER=1
+```
+
 If building with ```GPU``` support, add the following configuration to config.mk and build:
 ```bash
     echo "USE_CUDA = 1" >> ./config.mk
     echo "USE_CUDA_PATH = /usr/local/cuda" >> ./config.mk
     echo "USE_CUDNN = 1" >> ./config.mk
-    make
+    make -j$(sysctl -n hw.ncpu)
 ```
 **Note:** To change build parameters, edit ```config.mk```.
 

make/osx.mk

@@ -77,6 +77,7 @@ USE_CUDNN = 0
 USE_OPENCV = 1
 
 # use openmp for parallelization
+# apple-clang by default does not have openmp built-in
 USE_OPENMP = 0
 
 # choose the version of blas you want to use