A ticket open on OASIS Forum
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When running EC-Earth4 (OIFS+NEMO4) and I see an OASIS/MCT error that I do not recognise:

MCT::m_AttrVectComms::GSM_gather_: Input GlobalSegMap haloed--not allowed error, stat =1 03F.MCT(MPEU)::die.: from MCT::m_AttrVectComms::GSM_gather_() application called MPI_Abort(MPI_COMM_WORLD, 2) - process 63

This happens when I increase the number of cores for OIFS and NEMO. Not too many, just ca. 200+100. With less cores, the error doesn't happen. I do not know this error from our old model version. I use SCRIP/GAUSWGT interpolations. I have TREAT_OVERLAY activated, even though I think it is not needed for this mapping. I've heard that the error is known to other people using OASIS+NEMO, particularly when activating land domain removal. However, it never occurred to us in the old EC-Earth3 version, even with land domain removal activated. It has been suggested to comment out the test that triggers the error in lib/mct/mct/m_AttrVectComms.F90, and that works in my case.

Nevertheless, I would like to raise the problem here to encourage a more permanent solution. Thanks a lot in advance for your input!


* Eric Maisonnave had exactly the same problem at the MetOffice and he did exactly what you did. There is a ticket opened on the problem #2472 and we work on it.