linear_model app with UM_PHYSICS compiler flag set to true by cjohnson-pi · Pull Request #502 · MetOffice/lfric_apps

cjohnson-pi · 2026-05-20T08:10:47Z

PR Summary

Sci/Tech Reviewer: Steven Sandbach (@ss421)
Code Reviewer: James Bruten (@james-bruten-mo)

To allow the linear and nonlinear code to be run in the same executable, the linear_model code needs to be
able to run with UM_PHYSICS set to true. This includes requiring the physics code to be extracted during the build. I propose that given that the linear model will be used in this format operationally, the linear_model app should also be tested in this format.

The main changes are:

Updating the linear_model app makefile so that it is almost the same as the lfric_atm makefile, but with the addition of the linear code.
Use the lfric_atm app build and optimisation options. These are linked to directly from the linear_model app makefile (rather than copying into the linear_model application directories) - which will allow any changes to lfric_atm options to be immediately picked up by the linear_model app.
Add a few switches in the code (for the create_physics_prognostics), around the ifdef UM_PHYSICS that is now turned on.
Split up some of the code so that it is not called by the linear model. eg. create_prognostics and linear_diagnostics.

The jedi_lfric_tests application has not been updated. I have tried to update this in exactly the same way as the linear_model app and most of the tests pass. However, a few tests fail (e.g. run_jedi_lfric_tests_tlm_tests_nwp_gal9-4OMP-C12_MG_azspice_gnu_fast-debug-64bit). I believe that the reason for this is that the jedi_lfric_tests already have a optimisation/meto-azspice/psykal/global.py that is required for the adjoint code. Therefore it is not possible to simply point to the lfric_atm optimisation. A follow-on ticket will be required to update the jedi_lfric_tests. This will update the makefile so that it is similar to the linear_model app makefile, update the jedi_lfric_tests build and optimisation files so that they are combination of the lfric_atm and adjoint files. Also, the jedi_lfric_tests integration tests will need to be removed as I don't believe it is possible to run these with UM_PHYSICS.

blocks Enable jedi_lfric to run lfric_atm forecast configurations #512

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
[ x 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 - ifdef/run51

Suite Information

Item	Value
Suite Name	ifdef/run51
Suite User	christine.johnson
Workflow Start	2026-06-09T10:21:33
Groups Run	suite_default

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	MetOffice/jules@3647a42	True
lfric_apps	cjohnson-pi/lfric_apps@ifdefphys	False
lfric_core	MetOffice/lfric_core@bf23673	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 - 1198

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

DanStoneMO

Tested this against jedi and all works well. No linked jedi PR will be needed.

Steven Sandbach (ss421)

Thankyou for the update. This change is required by #512 which builds on this branch. Ive added a blocks PR to the summary.

I've added a few comments but happy with the change so Im handing the change over to James Bruten (@james-bruten-mo) for code review.

Steven Sandbach (ss421) · 2026-05-21T09:37:35Z

@@ -1,15 +1,19 @@
 ##############################################################################
-# (c) Crown copyright 2023-2024 Met Office. All rights reserved.


Im not sure what the policy is but I think the start date here should not change.

The makefile was copied from lfric_atm which has a start date of 2017. Happy to be advised by the code reviewer.

Steven Sandbach (ss421) · 2026-05-21T09:38:15Z

@@ -0,0 +1,45 @@
+##############################################################################
+# (c) Crown copyright 2017-2026 Met Office. All rights reserved.


If its a new file - should it just be 2026?

Not sure. It was copied from lfric_atm, which started with 2017. Happy to be advised by code reviewer.

Steven Sandbach (ss421) · 2026-05-21T10:12:22Z

 limit_cfl=.false.,
 /
 &section_choice
+aerosol='none',


Are these updated because they have been missed in previous updates?

Yes given that there is no physics, it seems safer to switch them all to none. In addition this then satisfies the new switch in create_physics_prognostics.

Thankyou. Is this already applied in the rose configurations?

Yes. Although some settings are not triggered (so it might have !!aerosol) due to the rose meta validation (which is not applied to the example configuration files).

Steven Sandbach (ss421)

Passing to James Bruten (@james-bruten-mo) for code review.

mo-cjsmith

Initialisation changes look fine.

James Bruten (james-bruten-mo)

I think this is mostly fine. I was slightly surprised at the number of changes required in gungho. I imagined that any physics initialisation required there was already done for the apps using the physics schemes? Similarly for the new create_physics_model_data subroutine?

cjohnson-pi · 2026-06-01T09:29:02Z

I think this is mostly fine. I was slightly surprised at the number of changes required in gungho. I imagined that any physics initialisation required there was already done for the apps using the physics schemes? Similarly for the new create_physics_model_data subroutine?

The reason for the changes in gungho is that currently when ifdef UM_PHYSICS is turned on, a lot of physics is initialised (which is required for lfric_atm). But we don't want to initialise this for the linear model as the linear model doesn't use physics. So I've tried to rearrange the code slightly so that the linear model doesn't call as much of the physics initialisation, and anything that it does call has an extra switch that can be turned off.

Its a bit of a peculiar code change. The linear model doesn't use physics which is why at the moment the UM_PHYSICS is not turned on. But as jedi need the linear and nonlinear models to be run in the same executable, we have to turn UM_PHYSICS on in the compilation. i.e. its turn it on but don't use it.

James Bruten (james-bruten-mo)

Thanks Christine, that makes sense so happy to approve.
Given this blocks the jedi PR I may ask another SSD member to get this on over the next few days as I'm away for the next week.

Matthew Hambley (MatthewHambley)

Code owner (buid system) review: A couple of questions regarding build system changes.

Matthew Hambley (MatthewHambley) · 2026-06-02T10:09:52Z

 export FFLAGS_UM_PHYSICS = -s real64

-include $(PROJECT_DIR)/build/fortran/crayftn/$(PROFILE).mk
+include $(PROJECT_DIR)/../lfric_atm/build/fortran/crayftn/$(PROFILE).mk


I don't understand the need for this change. Does it not do exactly the same thing as the original line but in a more complicated manner?

I'm now calling this lfric_atm file from the linear_model app. So when calling from the linear_model app, PROJECT_DIR=linear_model. But when calling from the lfric_atm app, PROJECT_DIR=lfric_atm. So you are correct that when running lfric_atm it does exactly the same thing.

This is a case of two files which have the same bytes not being the same file. If you need these files in "linear", copy them into linear.

It's important to understand that these files are largely for the benefit of the optimisation team and they will almost certainly need them to contain different bytes.

I have copied the build/fortran directory from lfric_atm to linear_model

Matthew Hambley (MatthewHambley) · 2026-06-02T10:10:33Z

+
+$(info UM physics specific compile options)
+
+include $(LFRIC_ATM_DIR)/build/fortran/$(FORTRAN_COMPILER).mk


I don't think there should be a need to do this. What is it achieving?

Hmm, I'm not exactly sure what it is achieving. My aim is to use the same compiler options as lfric_atm - so I just copied that over. I think that if its missing then there is a failure - although I would need to double check.

How did that check go?

Without this line, it doesnt compile. A variety of errors depending on the compiler. e.g. With cce_production-32bit,

ftn-1307 ftn: ERROR UKCA_RADAER_GET_LUT_INDEX_ARRAY, File = legacy/ukca_interface/ukca_radaer_lut_in.F90, Line = 162, Column = 22 The kind (4) of this actual argument does not match that of its associated dummy argument (8).

With gnu_production-64bit,

algorithm/random_seed_gen_alg_mod.f90:42:49: 42 | integer(i_def) :: year, month, day, utc_shift, hour, minute, & | 1 Error: Unused variable 'utc_shift' declared at (1) [-Werror=unused-variable]

Matthew Hambley (MatthewHambley)

Code owner (build system) review: Some small changes are needed.

Matthew Hambley (MatthewHambley) · 2026-06-08T11:58:14Z

 export FFLAGS_UM_PHYSICS = -s real64

-include $(PROJECT_DIR)/build/fortran/crayftn/$(PROFILE).mk
+include $(PROJECT_DIR)/../lfric_atm/build/fortran/crayftn/$(PROFILE).mk


This is a case of two files which have the same bytes not being the same file. If you need these files in "linear", copy them into linear.

It's important to understand that these files are largely for the benefit of the optimisation team and they will almost certainly need them to contain different bytes.

Matthew Hambley (MatthewHambley) · 2026-06-08T11:59:57Z

+
+$(info UM physics specific compile options)
+
+include $(LFRIC_ATM_DIR)/build/fortran/$(FORTRAN_COMPILER).mk


How did that check go?

cjohnson-pi · 2026-06-10T08:00:06Z

I have copied the build options from lfric_atm to linear_model and adjusted the makefile (also updates due to merge from main). The optimisation options in the makefile still point to the lfric_atm optimisation options. I have rerun the developer test-suite and added the trac.log above.

Matthew Hambley (MatthewHambley)

Code owner (build system) review: Changes to the build system appear to lack design or sustainability. However, they are being copied from badly designed and unsustainable changes made to Atmosphere. Since we are in the process of replacing this whole mess, making it worse will affect only this making the changes.

…reate_physics_model_data* routine; needs field_mapper to be made available from the original routine

cjohnson-pi added 15 commits May 12, 2026 16:57

Add ifdef UM_PHYS, linear_model example runs

42c51b7

retry copying optimisation from lfric_atm]

3f79afc

linear_model and lfric_atm run

f6f1a06

clearwhitespace

0f9e2be

removing PHYSICS_ROOT change

9bf79cb

increase build wallclock

5f68c17

Merge remote-tracking branch 'upstream/stable' into ifdefphys

70c1ce1

use_physics false

0efabc0

correct for validate_rose-meta. Test suite completes.

23a5abb

use lfric_atm optimisation options

eaaba2a

tidy

3d3e72e

revert jedi changes

bcad2f5

whitespace

db5d9a2

update build

339b0b0

Make switch less strict, for jedi tests

b9da623

cjohnson-pi requested review from a team, Matthew Hambley (MatthewHambley), Hacka Fett (christophermaynard), Joerg Henrichs (hiker), James Bruten (james-bruten-mo) and mo-cjsmith as code owners May 20, 2026 08:10

github-actions Bot assigned cjohnson-pi May 20, 2026

github-actions Bot requested review from Steven Sandbach (ss421) May 20, 2026 08:11

cjohnson-pi added this to the Summer 2026 milestone May 20, 2026

DanStoneMO approved these changes May 20, 2026

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Steven Sandbach (ss421) mentioned this pull request May 20, 2026

Enable jedi_lfric to run lfric_atm forecast configurations #512

Open

28 tasks

cjohnson-pi mentioned this pull request May 21, 2026

#474: LFRic-Nudging: Part-A: Introduce ability to read nudging datafiles #474

Merged

28 tasks

Steven Sandbach (ss421) approved these changes May 21, 2026

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mo-cjsmith approved these changes May 22, 2026

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James Bruten (james-bruten-mo) reviewed May 28, 2026

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James Bruten (james-bruten-mo) added 2 commits June 2, 2026 09:20

Merge branch 'main' into ifdefphys

fc48bb0

Fix indentation for extracting external metadata message

58011c4

James Bruten (james-bruten-mo) approved these changes Jun 2, 2026

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Matthew Hambley (MatthewHambley) reviewed Jun 2, 2026

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Matthew Hambley (MatthewHambley) requested changes Jun 8, 2026

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cjohnson-pi added 2 commits June 8, 2026 15:04

Copy build options from lfric_atm

1c0df0e

Updates since merge from main

1c551e7

James Bruten (james-bruten-mo) requested a review from Matthew Hambley (MatthewHambley) June 15, 2026 14:51

Matthew Hambley (MatthewHambley) approved these changes Jun 18, 2026

View reviewed changes

Merge remote-tracking branch 'origin/main' into ifdefphys

7d4cfe5

James Bruten (james-bruten-mo) merged commit 4532e9f into MetOffice:main Jun 19, 2026
5 checks passed

Mohit Dalvi (mcdalvi) added a commit to mcdalvi/lfric_apps that referenced this pull request Jun 22, 2026

Changes in response to MetOffice#502: create nudging fields in new *c…

3a821f9

…reate_physics_model_data* routine; needs field_mapper to be made available from the original routine

Mohit Dalvi (mcdalvi) added a commit to mcdalvi/lfric_apps that referenced this pull request Jun 22, 2026

Revert some of the changes made in response to MetOffice#502

5a9ce1a

		@@ -1,15 +1,19 @@
		##############################################################################
		# (c) Crown copyright 2023-2024 Met Office. All rights reserved.

		@@ -0,0 +1,45 @@
		##############################################################################
		# (c) Crown copyright 2017-2026 Met Office. All rights reserved.


		$(info UM physics specific compile options)

		include $(LFRIC_ATM_DIR)/build/fortran/$(FORTRAN_COMPILER).mk

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PR Summary

Code Quality Checklist

Testing

trac.log

Test Suite Results - lfric_apps - ifdef/run51

Suite Information

Task Information

Security Considerations

Performance Impact

AI Assistance and Attribution

Documentation

PSyclone Approval

Sci/Tech Review

Code Review

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cjohnson-pi commented Jun 1, 2026

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cjohnson-pi Jun 8, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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cjohnson-pi commented May 20, 2026 •

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