Turn on bl_segment by default for lfric_atm jobs

[MetBenjaminWent]

Turn on bl_segment by default for lfric_atm jobs by updating relevent versions.py

Blocking which is being enabled with changes to the boundary layer, see #106, are improving the use of the segmentaion blocking variable bl_segment, which is present in the source.

Testing has indicated a minor boost at 1T, and a good boost at higher thread counts.

This assists with cache blocking in the routines.

This ticket should follow changes in #325, as it contains the most uses of the variable.

PR Summary

Sci/Tech Reviewer: @christophermaynard
Code Reviewer:

Umbrella issue: #106
Closes #327

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 - bl_seg_size_versions/run3

Suite Information

Item	Value
Suite Name	bl_seg_size_versions/run3
Suite User	benjamin.went
Workflow Start	2026-03-20T13:39:14
Groups Run	all

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	MetOffice/jules@2026.03.2	True
lfric_apps	MetBenjaminWent/lfric_apps@bl_seg_size_versions	False
lfric_core	MetOffice/lfric_core@018e40c	True
moci	MetOffice/moci@2026.03.2	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2026.03.2	True
socrates	MetOffice/socrates@2026.03.2	True
socrates-spectral	MetOffice/socrates-spectral@2026.03.2	True
ukca	MetOffice/ukca@2026.03.2	True

Task Information

❌ failed tasks - 2

Task	State
run_gungho_model_deep-hot-jupiter-C24_MG_azspice_gnu_fast-debug-64bit	failed
run_gungho_model_tidally-locked-earth-C24_MG_azspice_gnu_fast-debug-64bit-crun0	failed

✅ succeeded tasks - 1502

Security Considerations

• I have reviewed my changes for potential security issues
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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