COSIMA TWG meeting minutes: Feb 2023

Summary of my notes from the COSIMA TWG meeting today. Please add whatever I’ve missed/misrepresented (this is a wiki post so can be directly edited, or add a comment below to expand or add additional points to topics that were raised)

Date : 2023-02-08
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Angus Gibson @angus-g, Harshula Jayasuriya @harshula, Aidan Heerdegen @aidanheerdegen, Siobhan O’Farrell @sofarrell


  • Restating of previous discussions. Choice between permissive and not-permissive has been made. Definitely want permissive. Now choice is between a license that requires changes to be contributed back when code is redistributed vs one where this is not required.
  • Decided need to provide these two choices and some contextual information, pros/cons etc, to main community to make decision. @micael agreed to start a topic outlining this information.


  • JRA55-do will stop being updated in the near future (link to definitive info?). Groups such as GFDL are looking to develop an ocean driving product based on ERA5. Potentially makes the work to integrate ERA5 forcing into ACCESS-OM2 even more important:
    – ACCESS-OM2 will no longer be able to be run with up to date forcing product to investigate recent events of scientific and/or societal importance
    – ACCESS-OM3 is less well characterised/understood, which makes evaluating a forcing product more difficult. Comparing both products in ACCESS-OM2 makes it easier to assess differences between them, informing OM3 work.

Update on ACCESS-OM3 source build

  • All components now building using CMake. Except the driver, not yet done. Was going to write one, then saw a generic driver was available, ESMx, will investigate using this.

MPI libraries on Gadi

  • @micael did some benchmarks using the Octopus code, which has some similarities with MOM6 (it solves time-dependent differential equations on a grid using finite-differences). He sees that Intel MPI is slower than OpenMPI for communication (as expected) but faster for the memory and CPU bound parts of the code (somehow surprising). Despite slower communication, this leads to faster overall times for one specific case, using ~1000 cores. For profiling of MOM6, we should make sure to test both libraries.

Update on progress with ACCESS-OM2 spack build

  • @harshula gave a short overview of what is needed to make a spack package file, which is required to build a software project with spack. Illustrated this with two examples: libaccessom2 which has a complete and well configured build system, and oasis3-mct which does not.
  • Entire ACCESS-OM2 build completes automatically in a few minutes on his laptop with gcc compiler.

Not quite: communications are slower with Intel MPI, but the CPU and memory bound parts of the code (i.e., the ones that don’t perform any communications) are faster.

1 Like

Please edit the post to reflect what you said @micael.

I think it is better to make the “minutes” as accurate as possible, rather than require readers to look at all the comments to get the full picture. Doesn’t mean you have to delete the comment, it is useful to know there was a problem that was updated.

Thanks for the correction, I must’ve misunderstood you. That seems even weirder than I thought!