Remove j and block ex coef

[MetBenjaminWent]

PR Summary

Sci/Tech Reviewer: @christophermaynard
Code Reviewer: @mo-alistairp

Remove the j loop which is adversely affecting performance in the boundary layer, and improve blocking loops.

• Performance data can be found in the umbrella issue, Boundary Layer Umbrella #106
• closes Remove j loop ex_coef #216

NOTE - it seems that the C12 fast debug 2T run is being affected by a KGO change. No other OMP, or developer test is failing it's KGO.
The all group will be run with final commits moving into SR, this will also need a Science approval for the KGO.

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 - ex_coef/run39

Suite Information

Item	Value
Suite Name	ex_coef/run39
Suite User	benjamin.went
Workflow Start	2026-02-18T16:36:51
Groups Run	developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	MetBenjaminWent/lfric_apps@ex_coef	False
lfric_core	MetOffice/lfric_core@88533c5	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

❌ failed tasks - 3

Task	State
run_adjoint_tests_nwp_gal9-C12_MG_azspice_gnu_production-32bit	failed
run_gungho_model_schar_cart-BiP200x8-500x500_azspice_gnu_fast-debug-64bit	failed
run_shallow_water_williamson2_vi-C24_azspice_gnu_fast-debug-64bit	failed
Failed tests are timeouts, and unrelated to changes. Given trunk failings for KGO which have muddied this ticket already, if these are still an issue for the reviewers, I'll take a further look.

🚫 submit-failed tasks - 1

Task	State
run_gungho_model_baroclinic-alt3-C24_MG_azspice_gnu_fast-debug-64bit-rtran32	submit-failed

✅ succeeded tasks - 1156

Test Suite Results - lfric_apps - ex_coef/run30

Suite Information

Item	Value
Suite Name	ex_coef/run30
Suite User	benjamin.went
Workflow Start	2026-02-17T16:11:02
Groups Run	ex1a_omp_developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	MetBenjaminWent/lfric_apps@ex_coef	False
lfric_core	MetOffice/lfric_core@88533c5	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

✅ succeeded tasks - 51

Test Suite Results - lfric_apps - ex_coef/run6

Suite Information

Item	Value
Suite Name	ex_coef/run6
Suite User	benjamin.went
Workflow Start	2026-02-05T16:38:01
Groups Run	developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	MetBenjaminWent/lfric_apps@ex_coef	False
lfric_core	MetOffice/lfric_core@bbb3d8a	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

❌ failed tasks - 5

Task	State
check_lfric_atm_nwp_gal9_2T-C12_ex1a_cce_fast-debug-32bit	failed
kgo_groups_checker	failed
run_gungho_model_lfric-real-domain-C48_MG_azspice_gnu_fast-debug-64bit	failed
run_gungho_model_sbr-alt2-C24_MG_op_azspice_gnu_fast-debug-64bit	failed
run_jedi_lfric_tests_tlm_tests_default-relaxed_solver-1PE-C12_azspice_gnu_fast-debug-64bit	failed

✅ succeeded tasks - 1096

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

[MetBenjaminWent]

C12 - 2T seems to be failing KGOs in testing.

All others are fine, as are run throughs. Reverting all changes fixes KGO.

Investigation WIP.

[MetBenjaminWent]

Test Suite Results - lfric_apps - ex_coef/run19

Suite Information

Item	Value
Suite Name	ex_coef/run19
Suite User	benjamin.went
Workflow Start	2026-02-13T09:13:32
Groups Run	ex1a_omp_C12_full_cce

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	MetBenjaminWent/lfric_apps@ex_coef	False
lfric_core	MetOffice/lfric_core@bbb3d8a	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

✅ succeeded tasks - 10

[MetBenjaminWent]

KGO for C12 full holds

[MetBenjaminWent]

Examples of changes in listing files:

[MetBenjaminWent]

Copies of listing files:
ex_coef_post_changes.txt
ex_coef_pre_changes.txt

[MetBenjaminWent]

Post a KGO update, fast holds too:

Test Suite Results - lfric_apps - ex_coef/run23

Suite Information

Item	Value
Suite Name	ex_coef/run23
Suite User	benjamin.went
Workflow Start	2026-02-16T11:34:33
Groups Run	ex1a_omp_C12_cce

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	MetBenjaminWent/lfric_apps@ex_coef	False
lfric_core	MetOffice/lfric_core@bbb3d8a	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

✅ succeeded tasks - 18

[MetBenjaminWent]

All liner_model seem to be failing now, including full-debug

I've checked the namelist for liner_model, and have had a look in sections under those flags, they should be fine.

I did expand OMP coverage, possibly to sections which under a flag may never use it. (However PSyclone will likely do the same).
These tests are not threaded, so there shouldn't be an interaction there.

These have always occured with the removal of the j loop, so there could be something I've missed, where j is required.

But given how localised it is to just liner_model, this should be easier to spot in theory, but it isn't.

[MetBenjaminWent]

All liner model KGO issues seem related to issues on trunk, as latest tests run through fine.

With this in mind, I'm going to push this to review this morning, as I am getting consistent enough results, that only that C12 test is failing KGOs, and the rest of the issues are trunk related.

[Adrian-Lock]

That's all fine.