How to run BATS in Mac

Run BATS in Linux is easy, but on Mac is hard. The main problem is caused by different compliers in these two operation systems: gcc for Linux and clang for Mac. This blog will help you install and run it on Mac.

C++ (BATS)

If you use Linux OS, then simply run use the flag -fopenmp like

g++ -o hello_omp.out hello_omp.cpp -fopenmp

If you use Mac OS, then run the following might work depends on your g++ setting:

g++-10 -o hello_omp.out hello_omp.cpp -fopenmp

However, if you are not lucky enough, it probably cause some problems, because your g++ is not configured correctly (OpenMP might be the biggest problem). If so, please see below.

Error: If you use g++ -o hello_omp.out hello_omp.cpp -fopenmp in Mac and get an error like clang: error: unsupported option '-fopenmp', this is because g++ in Mac is default to use clang (e.g., Apple clang version 12.0.0 (clang-1200.0.32.29) in my case).

The bad thing is Mac use clang as an alias for g++, and using OpenMP is hard in clang. You will need Homebrew to install GCC. The details of installation is listed below:

• Install gcc by Homebrew

  brew install gcc
  

  Find the location of the newly installed gcc. Brew appends the version number to gcc so that it does not conflict with the one installed by Command Line Tools. You will find it in usr/local/bin. In my case it’s usr/local/bin/gcc-10.

There are two options from now on:

1. Change setting in ~/.zshrc for a user-wide setting. Because calling a compiler your bash will look into /usr/bin by default and not in /usr/local/bin, you can add this directory to your $PATH. This can be easily done with the command:

vim ~/.zshrc

and then in the almost end of that file, change

export PATH=/usr/local/bin:$PATH

1. You are also able to export a sesstion environment varible by export CXX=/usr/local/bin/g++-10 in terminal. However, next time if you reopen a terminal and want to use g++ from GNU instead of clang, make sure you change the environment variable again.

Finally, in order to use makefile, change CXX flags into CXX = g++-10. Now, you are free to compile it.

Python(BATS.py)

Note: Since BATS.py is a python extesion based on C++, you need to set the complier of C++ in your Mac correctly. Thus, you need to finish the above setting before continue. It is easy, simply add two choice of C++ and C complier before python installation.

CXX=g++-10 CC=gcc-10 python setup.py install

If you have developed it, i.e., changed the submodule BATS, then use

CXX=g++-10 CC=gcc-10 python setup.py build_ext --inplace
CXX=g++-10 CC=gcc-10 python setup.py build_ext -f -j4
CXX=g++-10 CC=gcc-10 python setup.py install