IO_Demo benchmarking configuration

[EdHone]

PR Summary

Sci/Tech Reviewer: @andrewcoughtrie
Code Reviewer: @mo-lucy-gordon

This change introduces a flexible benchmarking configuration for the IO_Demo app. The new functionality enables a user to specify a number of fields to write, along with a number of seconds to wait during a step to mimic simulation time. This simple configuration should enable us to exercise the LFRic I/O capability for a number of different use-cases, including writing data at scale.
The changes include:

• source changes in io_demo to enable new benchmark capability
• changes to build the app which enable the use of the sleep() intrinsic for all compilers
• changes to io_demo metadata which allow the app to be controlled a bit more intuitively
• tweaks to the io_demo algorithm layer to enable it to be stable at scale
• tweaks to launch-exe to enable running with XIOS servers in the lfric_core rose-stem
• new rose-stem tests, along with a new io_demo_benchmark group which runs at large-ish scale (C224)

• closes IO_Demo benchmark configuration #216

Code Quality Checklist

(Some checks are automatically carried out via the CI pipeline)

• 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

Testing

• I have tested this change locally, using the LFRic Core rose-stem suite
• If required (e.g. API changes) I have also run the LFRic Apps test suite
  using this branch
• 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_core - lfric_core-216-iodemo-bench-vernier/run7

Suite Information

Item	Value
Suite Name	lfric_core-216-iodemo-bench-vernier/run7
Suite User	edward.hone
Workflow Start	2026-01-21T10:28:40
Groups Run	developer

Dependency	Reference	Main Like
lfric_core	EdHone/lfric_core@216-iodemo-bench-vernier	False
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True

Task Information

✅ succeeded tasks - 377

Test Suite Results - lfric_core - lfric_core-216-iodemo-bench-vernier/run6

Suite Information

Item	Value
Suite Name	lfric_core-216-iodemo-bench-vernier/run6
Suite User	edward.hone
Workflow Start	2026-01-21T10:17:45
Groups Run	io_demo_benchmark

Dependency	Reference	Main Like
lfric_core	EdHone/lfric_core@216-iodemo-bench-vernier	False
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True

Task Information

✅ succeeded tasks - 10

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
  tooscollabdevteam@metoffice.gov.uk

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

[MatthewHambley]

Presumed code owner review: The "allow everything" argument is a bit over broad but for a demo application and until we can work out how we actually want to handle the issue of "sleep", I am content.

[andrewcoughtrie]

This all looks fine to me. As mentioned in person could you open an issue to create a sleep function that wraps around C usleep or similar.

[EdHone]

This all looks fine to me. As mentioned in person could you open an issue to create a sleep function that wraps around C usleep or similar.

Done - #241

[EdHone]

I've just added 2 more commits which just change some of the rose-stem infrastructure around the tests:

• to copy the vernier output to the task output dir
• to only output a single file from vernier

I don't think these changes should require further science review, so I'll pass over to @mo-lucy-gordon for CR