[petsc-users] How to specify different MPI communication patterns.

[Randall Mackie]

Dear PETSc team,

A few years ago we were having some issue with MPI communications with large numbers of processes and subcomms, see this thread here:

https://urldefense.us/v3/__https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2020-April/040976.html__;!!G_uCfscf7eWS!fyPrzMKC4KZmxGO-HI0xUlOCbgwXod4O8q2h_6MjHqPLPj9ppLkgFkJUig-KqXgu6AX7pMhYtEpWOP_cCesCWcCk_Q$ 

We are once again encountering strange issues when running our code on a new cluster and after a month of various tests we have not found a solution, but we think it has something to do with network traffic and high MPI communications, similar perhaps to the thread from 3 years ago.

Is it still possible to change the communication pattern with the option -build_twosided_allreduce (and is that the right syntax?).

Are there other runtime options that we can try to change the MPI communication type for all underlying communications?


Thank you,

Randy M.


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