Remove tasks per node from OMP performance groups

[Benjamin Went (MetBenjaminWent)]

PR Summary

Remove ranks/tasks per node from the OMP developer groups, so that they can be effectively run on the Genoa nodes.

Sci/Tech Reviewer: Joseph Abram (@J-J-Abram)
Code Reviewer: mo-marqh

Code Quality Checklist

• I have performed a self-review of my own code
• My code follows the project's style guidelines
• Comments have been included that aid understanding and enhance the readability of the code
• My changes generate no new warnings
• All automated checks in the CI pipeline have completed successfully

Testing

• I have tested this change locally, using the LFRic Apps rose-stem suite
• If any tests fail (rose-stem or CI) the reason is understood and acceptable (e.g. kgo changes)
• I have added tests to cover new functionality as appropriate (e.g. system tests, unit tests, etc.)
• Any new tests have been assigned an appropriate amount of compute resource and have been allocated to an appropriate testing group (i.e. the developer tests are for jobs which use a small amount of compute resource and complete in a matter of minutes)

trac.log

Test Suite Results - lfric_apps - remove-rpn-omp-tasks/run1

Suite Information

Item	Value
Suite Name	remove-rpn-omp-tasks/run1
Suite User	benjamin.went
Workflow Start	2026-07-06T10:23:12
Groups Run	ex1a_omp_developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	MetOffice/jules@1ea67b4	True
lfric_apps	MetBenjaminWent/lfric_apps@remove-rpn-omp-tasks	False
lfric_core	MetOffice/lfric_core@5d6b2db	True
moci	MetOffice/moci@2026.03.2	True
SimSys_Scripts	MetOffice/SimSys_Scripts@3e2998b	True
socrates	MetOffice/socrates@2026.03.2	True
socrates-spectral	MetOffice/socrates-spectral@2026.03.2	True
ukca	MetOffice/ukca@1cdb9c2	True

Task Information

✅ succeeded tasks - 51

Security Considerations

• I have reviewed my changes for potential security issues
• Sensitive data is properly handled (if applicable)
• Authentication and authorisation are properly implemented (if applicable)

Performance Impact

• Performance of the code has been considered and, if applicable, suitable performance measurements have been conducted

AI Assistance and Attribution

• Some of the content of this change has been produced with the assistance of Generative AI tool name (e.g., Met Office Github Copilot Enterprise, Github Copilot Personal, ChatGPT GPT-4, etc) and I have followed the Simulation Systems AI policy (including attribution labels)

Documentation

• Where appropriate I have updated documentation related to this change and confirmed that it builds correctly

PSyclone Approval

• If you have edited any PSyclone-related code (e.g. PSyKAl-lite, Kernel interface, optimisation scripts, LFRic data structure code) then please contact the TCD Team

Sci/Tech Review

• I understand this area of code and the changes being added
• The proposed changes correspond to the pull request description
• Documentation is sufficient (do documentation papers need updating)
• Sufficient testing has been completed

(Please alert the code reviewer via a tag when you have approved the SR)

Code Review

• All dependencies have been resolved
• Related Issues have been properly linked and addressed
• CLA compliance has been confirmed
• Code quality standards have been met
• Tests are adequate and have passed
• Documentation is complete and accurate
• Security considerations have been addressed
• Performance impact is acceptable

[Benjamin Went (MetBenjaminWent)]

Here is a snippet example after running the ex1a_omp_developer group, with Genoa -S USE_GENOA=true

Launch command now runs correctly:

Note that this is a snippet from the 4t run, which is in the tasks list here (which this PR modifes, as well as the 2T):
https://github.com/MetOffice/lfric_apps/blob/main/rose-stem/site/common/lfric_atm/tasks_lfric_atm.cylc
nwp_gal9_3n_2T-C192_MG
nwp_gal9_3n_4T-C192_MG

The OMP_NUM_THREADS interaction is handled by the launch-exe:
https://github.com/MetOffice/lfric_apps/blob/main/rose-stem/site/meto/common/bin/launch-exe
Which is populated by the threads task setting and handles the -d setting for the launching of the lfric application application.

The cores/tasks per node (-ppn) were setup relative to the thread scaling, and initially assumed to be required. They are not.

[Joseph Abram (J-J-Abram)]

Happy with changes. Did a quick run to test and all passed.

[Wolfgang Hayek (tinyendian)]

We don't currently run this test, but looks good to me.