What version of GCC is required for the latest version of mfix compilation
No compiler is needed if you just want to install MFiX and use the built-in solver module. This will run common cases, but will not handle SMP or DMP or user-coded reaction rates, etc - that requires a custom solver.
To build the custom solver, you need GFortran.
I think the minimum version of GFortran which supports the -march=haswell flag is 4.9.2, although I suggest using the most recent version you can (we use GFortran 12.2.1). Some people have worked around this by modifying the CMake files to omit this flag.
Note that on Windows, we automatically install GFortran 5.3.1 along with MFiX since we don’t expect Windows users to have a Fortran compiler. (Unfortunately 5.3.1 is the most recent version available for Windows).
On Linux systems we have not included a Fortran compiler because we expect the platform to include one. However we are starting to reconsider this - some Linux systems such as Centos7 and Ubuntu come with old Fortran compilers and upgrading them is not always easy. And conda-forge (the package repository we use for MFiX) includes GFortran 12.2.0 - so future MFiX releases will probably bundle that.
In the meanwhile - after you install mfix-23.1 you can do:
$ conda activate mfix-23.1
$ conda install -c conda-forge gfortran
and you will get GFortran 12.2.0. (You can substitute mamba for conda if you have it installed)