Comment (by Roland Haas):

Please see the discussion in http://lists.einsteintoolkit.org/pipermail/users/2020-April/007388.html

While the Einstein Toolkit can build its own MPI stack as a fallback solution, it will preferentially use an already installed MPI. However if multiple MPI stacks are installed (and they are not set up correctly) the automatic detection will fail.

This happens to you on a freshly installed Ubuntu 18.04 system, did you install anything beyond the packages requested in https://github.com/nds-org/jupyter-et/blob/master/CactusTutorial.ipynb ?

If you want to force the toolkit to built its own MPI stack, then you will have to edit the OptionList file to include MPI=BUILD and add PATH=@SOURCEDIR@/exe/@CONFIGURATION@:$PATH to the RunScript file that is configs/sim. The build from scratch using:

make sim-clean
./simfactory/bin/sim build --reconfig

Please keep in mind that compiling one’s own MPI stack is mostly untested.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2372/fatal-error-in-pmpi_comm_rank-invalid