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2021-04-05Fix No-MPI Build Warning (#1870)Gravatar Axel Huebl 1-1/+4
Fix unused variable warnings in no-MPI builds.
2020-09-17MPI: Init or Thread Multiple (#1298)Gravatar Axel Huebl 1-0/+58
Simplify MPI init options to be independent of PSATD selection. Our use of FFTD only uses the non-threaded FFTW routines. Thread multiple is currently only needed for async I/O with AMReX plotfiles. Some MPI implementations allow to set the requested thread level with `mpiexec` and/or pre-compiled variants of the lib and/or through an environment variable, according to the standard. For example, `MPICH_THREADLEVEL_DEFAULT` in MPICH (and derivatives have similar names). This is done through an intricate upgrade/downgrade logic for the provided argument (sec. 12.4.3). We print a warning if the requested support level is not provided and a note if a stricter support level is provided.