I have the following, rather unusual, scenario... I have a program running with OpenMP on a multicore computer. At one point in the program, I want to use an external package that is written to exploit MPI, not OpenMP, parallelism. So a (rather awkward) solution could be to launch the program in MPI, but most of the time, everything is being done in a single MPI process, which is using OpenMP (ie, run my current program in a single MPI process). Then, when I get to the part where I need to use the external package, distribute out the information to all the MPI processes, run it across all, and then pull them back to the master process. This is awkward, but probably better than my current approach, which is running the external package on a single processor (ie, not exploiting parallelism in this time-consuming part of the code).
If I use this strategy, I fear that the idle MPI processes may be consuming clock cycles while I am running the rest of the program on the master process with OpenMP. Thus, they may compete with the OpenMP threads. OpenMP does not close threads between every pragma, but OMP_WAIT_POLICY can be set to sleep idle threads (actually, this is the default behavior). I have not been able to find any equivalent documentation regarding the behavior of idle threads in MPI. Best regards, Mark
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