The looping macros defined in cctk_Loop.h use OpenMP unconditionally. If a thorn is not using OpenMP, or is using OpenMP in a manner incompatible with cctk_Loop.h, then this can lead to segfaults. For example, cctk_Loop.h uses omp single (that prevents certain code from executing) or omp for (which parallelizes part of the loops). There should be a mechanism to disable this OpenMP parallelization.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2444/make-it-possible-to-disable-openmp-in-the