Cannot do parallel builds

[pbosler]

Running make -j so that PartMC is built in parallel decreases compilation times, but is currently unavailable. Errors like

f951: Fatal Error: Cannot rename module file ‘pmc_util.mod0’ to ‘pmc_util.mod’: No such file or directory
compilation terminated.

imply that a module that depends on pmc_util.mod is being built before pmc_util.mod has been compiled. Several errors like this (but with different specific filenames) suggest that CMake is having a hard time resolving dependencies between different PartMC modules.

Serial builds (with just make) work fine.

[slayoo]

Thanks for reporting it.

This seems to be a known CMake issue:

• https://gitlab.kitware.com/cmake/cmake/-/issues/17044
• https://gitlab.kitware.com/cmake/cmake/-/issues/22898
• https://stackoverflow.com/questions/29728867/cmake-parallel-build-for-fortran-90-with-modules

It seems that CMake does not support "-j" for Fortran code without refactoring the CMake instructions to be concurrency-safe. PartMC has a lot of module-providing sources, so IIUC, we would need to refactor CMakeLists.txt in a way that essentially each .F90 file has its own target with Fortran_MODULE_DIRECTORY and target_include_directories set accordingly to a "private" module directory (i.e., 50+ new targets).