MetOffice / MetOffice/lfric_apps
The combination of threading and MPI regions that cross cubed-sphere panel edges is not bit-reproducible
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- Dominant language
- Fortran
- Stars
- 31
- Forks
- 118
- Avg merge
- 2d 4h
- Merged PRs (30d)
- 8
Description
Are there any linked Issues or Pull Requests?
What happened?
It was found that after #138 was merged, that the gungho_model_baroclinic-C48_MG-3panel_azspice_gnu_fast-debug-64bit would sporadically produce different KGOs.
This will be avoided for now on main by setting the test to use a single thread (#293) but this suggests that tests which use both threading and have MPI regions that cross cubed-sphere panel edges are not bit-reproducible. My best hypothesis for now is that it relates to https://github.com/MetOffice/lfric_core/issues/252
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the gungho_model_baroclinic-C48_MG-3panel_azspice_gnu_fast-debug-64bit test configuration and review linked issues #252 and #293. Reproduce the run with threading enabled and MPI regions crossing cubed-sphere panel edges, then identify and resolve the source of differing KGOs so repeated runs are bit-reproducible.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- fortran
- Domain
- distributed-systems, testing-qa
- Issue type
- Bug
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100