Xgboost: How to install OpenMP version in R (Mac OS)

re: Makevars...I made the changes in ~/.R/Makevars. In addition to the SHLIB flags, I had to change to compiler to "clang-omp". For the compiler I used brew to install the version of clang that supported OpenMP.

I finally get this to work by using following code modified from @jimthompson5802 's answer. The code is put into ~/.R/Makevars:

CC=gcc-5
CXX=g++-5
CXX1X = g++-5

SHLIB_OPENMP_CFLAGS= -fopenmp
SHLIB_OPENMP_CXXFLAGS= -fopenmp
SHLIB_OPENMP_FCFLAGS= -fopenmp
SHLIB_OPENMP_FFLAGS= -fopenmp

In my case R would search/Library/Frameworks/R.framework/Resources/etc/Makeconf for necessary parameters undefined in ~/.R/Makevars. It would try to find the setting for CXX1X in Makeconf. So that is where the clang++ complier come from in the errors in my previous post.

I get a bunch of [-Wunused-variable] warnings but I guess it's fine. No OpenMP is not available warning this time.

Also since I have followed the official building instructions for mac os, I have gcc installed and with it I successfully built the "main" xgboost with OpenMP before. Thus I suggets for anyone who have followed the same instructions like me have their Makevars set up like this.

In my case, I have to set up more CXX to make it work:

CC=gcc-7
CXX=g++-7
CXX1X=g++-7
CXX11=g++-7
CXX14=g++-7
CXX17=g++-7

SHLIB_OPENMP_CFLAGS= -fopenmp
SHLIB_OPENMP_CXXFLAGS= -fopenmp
SHLIB_OPENMP_FCFLAGS= -fopenmp
SHLIB_OPENMP_FFLAGS= -fopenmp