OpenMP is a threading option built into GCC/Intel compilers.
https://www.openmp.org/resources/openmp-compilers-tools/
- OpenMP 4.5 C/C++/Fortran supported in version 17.0 compilers
- OpenMP 4.5 C/C++/Fortran supported in version 18.0 compilers
- Compile with -Qopenmp on Windows, or just -openmp or -qopenmp on Linux or Mac OS X / macOS