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#2727 (mpp_nc_generic+BDY not yet implemented with suppressed land subdomain close to the open boundary) – NEMO

#2727 closed Bug (fixed)

mpp_nc_generic+BDY not yet implemented with suppressed land subdomain close to the open boundary

Reported by: amoulin Owned by: systeam
Priority: normal Milestone:
Component: MULTIPLE Version: trunk
Severity: minor Keywords:
Cc: tomas.lovato@…

Description (last modified by lovato)


An error appears in the MEDITERRANEAN configuration using a domain decomposition with suppressed land subdomain close to the open boundary.


The problem could be reproduced using AMM12 configuration with for example 216 proc (no definition of jpni jpnj in nammpp namelist):

Number of mpi processes: 216
Number of ocean subdomains = 216
Number of suppressed land subdomains = 64

A suppressed subdomain is defined as a neighbour of the south open boundary and lead to the message error defining in lbc_lnk_neicoll_generic.h90:

===>>> : E R R O R

mpp_nc_generic+BDY not yet implemented

huge E-R-R-O-R : immediate stop



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AMM12_180proc_216proc.jpg (256.9 KB) - added by lovato 20 months ago.

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Change History (4)

Changed 20 months ago by lovato

comment:1 Changed 20 months ago by lovato

  • Description modified (diff)
  • Priority changed from low to normal

comment:2 Changed 20 months ago by smasson

The problem is not related to the suppression of land domains. You have the same stop if you use 280 cores and you fix in the namelist: jpni = 20 and jpnj = 14.
The problem is coming from the geometry of the domain decomposition you use. You unfortunately pick-up a domain decomposition which requires an MPI communication in BDY (because you have somewhere an MPI boundary that is located just along the coast line).
Today, collective communication (nn_comm = 2) are incompatible with the communications used in BDY (which involves only a few processes). So we put this stop!
2 solutions:

  • hard one: add in mpp_ini_nc a specific communicator for BDY
  • easy one: once you enter BDY, you force nn_comm = 1, so you use point-to-point communication. You move back nn_comm to 2 onces you leave BDY.

comment:3 Changed 20 months ago by amoulin

  • Resolution set to fixed
  • Status changed from new to closed

No problem anymore as nn_comm=1 can be used with BDY now thanks to Sebastien's corrections in the ticket #2731 (trunk revision 15368).

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