MPI and OpenMP on Apple Silicon M1 Pro

Question

So, someone has to initiate such a question regarding apple silicon. Long story short, I need to compile and run a C++ code that runs hybrid with both MPI and OpenMP on a MBP M1 pro (which uses arm-based architecture). The code runs perfectly fine on a typical Intel x86 architecture. Also, for completion sake, the Mac OS is Monterey. Additionally, I do not compile/run via an IDE (e.g. XCode), I do so via a Makefile, directly from the terminal.

I haven't found a clear answer to such a question. I tried setting things up myself, but this is way above my comfort zone. Moreover, I trust answering such a question would help future developers that are using these Macs for work :)

So far, I understood that the installed Clang compiler that comes with Xcode does not support OpenMP (-fopenmp) or recognizes MPI (mpirun). So, I installed "brew" and the "llvm" version which should support the multi-threading instructions via OpenMP. As for the MPI library, I installed the "libomp" library through "brew". These all should run natively on Apple Silicon.

However, now the environment is all over the place, since the system has 2 Clang compilers:

• one preinstalled with Xcode (the default)
• one installed via brew, situated in: /opt/homebrew/opt/llvm

I do not know how to proceed. The simple solution might be to change the path of the compiler to that in the /opt/homebrew/ directory, however I suspect that might mess a lot of things in the system.

I would (and many others) be very thankful if you could help, in case someone has prior experience with something like this before.