Performance optiimisation: Add debug flags, and target cascadelake

[manodeep]

Do not merge - I am using this to test performance with various compiler flag combos. Test-bed is with a 20-day run of the 25k IAF config.

debug flags

The -g3 -grecord-gcc-switches -fno-omit-frame-pointer are good to have and do (should?) not have any meaningful impact on performance. We might have to apply the -fno-omit-frame-pointer after the optimisation flag (-O2 here), since -O1/-O2/etc implies -fomit-frame-pointer (which will presumably cancel out the previous flag). Similarly, -g implies -fno-omit-frame-pointer

optimisation flags

Based on testing with OM2, the -xCORE-AVX2 flags produced a 5-10% performance improvement compared to -mavx2/-march=haswell etc. Testing whether a similar performance boost occurs by replacing -march=sapphirerapids -mtune=sapphirerapids with -xcascadelake

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🚀 The latest prerelease access-om3/pr210-2 at 8d863ee is here: #210 (comment) 🚀

[github-actions]

The model version in the spack.yaml has not been updated.
You can update it manually.
Alternatively, comment the following to have it updated and committed automatically:

• !bump major for feature releases
• !bump minor for bugfixes

[github-actions]

🚀 Attempted to deploy access-om3 Prerelease pr210-1 with commit 630e87c

🖥️ Gadi Deployment ❌

[github-actions]

🚀 Attempted to deploy access-om3 Prerelease pr210-1 with commit 630e87c

🖥️ Gadi Deployment ✔️

Usage Instructions

access-om3, defined in spack.yaml, will be deployed to Gadi as:

• 2026.03.000 as a Release (when merged).
• pr210-1 as a Prerelease (during this PR).

This Prerelease is accessible on Gadi using:

module use /g/data/vk83/prerelease/modules
module load access-om3/pr210-1

When using the above modules, the binaries shall be on your $PATH.

For advanced users, this Prerelease is also accessible on Gadi via /g/data/vk83/prerelease/apps/spack/1.1/spack in the access-om3-pr210-1 environment.
Due to inode-saving measures, one will have to manually untar the environment metadata before environment activation with tar -xf .spack-env .spack-env.tar. It will require one to have write privileges.

Configuration Information

This Prerelease is deployed using:

• access-nri/spack on branch 1.1
• spack/spack-packages version 383e969358c951abe17623696083e6f862c4488e
• access-nri/access-spack-packages version 2026.03.003
• access-nri/spack-config version 2026.02.003

If the above was not what was expected, commit changes to config/versions.json in this PR, or propose changes to build-cds config/settings.json.

[dougiesquire]

What was the namelist error @manodeep? The WOMBATlite namelist does need to be updated with these versions. See https://github.com/ACCESS-NRI/access-om3-configs/pull/1225/changes#diff-864e627df2bf0220849373d949dfe5de1979c09c25b0eac03f7c8c647e92c89e

[dougiesquire]

Also fd.yaml and datm_in will need to be updated for things to run I believe. Which config are you trying to run?

[github-actions]

🚀 Attempted to deploy access-om3 Prerelease pr210-2 with commit 8d863ee

🖥️ Gadi Deployment ✔️

Usage Instructions

access-om3, defined in spack.yaml, will be deployed to Gadi as:

• 2026.03.000 as a Release (when merged).
• pr210-2 as a Prerelease (during this PR).

This Prerelease is accessible on Gadi using:

module use /g/data/vk83/prerelease/modules
module load access-om3/pr210-2

When using the above modules, the binaries shall be on your $PATH.

For advanced users, this Prerelease is also accessible on Gadi via /g/data/vk83/prerelease/apps/spack/1.1/spack in the access-om3-pr210-2 environment.
Due to inode-saving measures, one will have to manually untar the environment metadata before environment activation with tar -xf .spack-env .spack-env.tar. It will require one to have write privileges.

Configuration Information

This Prerelease is deployed using:

• access-nri/spack on branch 1.1
• spack/spack-packages version 383e969358c951abe17623696083e6f862c4488e
• access-nri/access-spack-packages version 2026.03.003
• access-nri/spack-config version 2026.02.003

If the above was not what was expected, commit changes to config/versions.json in this PR, or propose changes to build-cds config/settings.json.

[manodeep]

@dougiesquire I am using the 25km IAF config. Both the 24th Feb and 17th March versions had this error on startup:

  (atm_comp_nuopc):(InitializeAdvertise) : namelist read error datm_in rc=      
     19

[dougiesquire]

I think you'll need the changes in ACCESS-NRI/access-om3-configs#1225 (merged into the 25km IAF WOMBATlite config yesterday). I believe @anton-seaice is updating the other configs as we speak

[anton-seaice]

See ACCESS-NRI/access-om3-configs#1232

[manodeep]

Thanks both!

[manodeep]

Can confirm that run with the first deployment is running successfully after cloning from the cherry-picked 1232 pr.