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2020WP/HPC-04_mcastril_Mixed_Precision_implementation – NEMO

Version 7 (modified by mcastril, 4 years ago) (diff)



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  1. Summary
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  3. Tests
  4. Review


Action HPC-04_mcastril_Mixed_Precision_implementation
PI(S) Miguel Castrillo, Oriol Tintó
Digest To implement mixed precision in NEMO OCE
Dependencies WP 2008 HPC-13_Mixed_precision_study-13.1_Assessment (completed)
Branch source:/NEMO/branches/2020/dev_r12512_HPC-04_mcastril_Mixed_Precision_implementation
Previewer(s) Mike Bell, Sébastien Masson
Reviewer(s) Mike Bell, Sébastien Masson
Ticket #2364


The use of mixed precision can provide a substantial speed-up for models in which the numerical precision has been overengineered. This speedup can come as a result of improvements in both computing and memory efficiency.

This action is a follow up from HPC-08_Mixed_precision in 2018 WP. It was linked to two tickets (#2039 and #2040), that were respectively devoted to the assessment and implementation of Mixed Precision in NEMO. After the evaluation stage has been completed (together with the preparation of the necessary tools to do the mentioned assessment and the implementation), this year will be time for the implementation.

Oriol Tintó (oriol.tinto@…) is the Principal Investigator for the whole task. ECMWF is a collaborator for this phase and will have a principal role on the validation in coupled simulations.

The analysis procedure is documented in the following publication:


The implementation will follow the steps below:

a) BSC developing a prototype based on NEMO 4.0.1; Further testing done at ECMWF with this version. At this stage the prototype is ready to test.

b) Provide demonstrator for NEMO ST (how? => Scientific Publication, Branch in NEMO rep.) (BSC)

c) Prepare tools for automation to make sure that all the workflow that goes from identifying sensitive variables to a final implementation can be reapplied to any version of the code. (BSC, April 2020)

d) Provide a mixed-precision branch at the NEMO SVN starting after the merging party. (BSC, April 2020)

e) Provide scientific evaluation and progress idealised test cases motivated by single precision evaluation and beyond (throughout 2020) (ECMWF); (Discussion on intercomparison test cases at Commodore Workshop, January 2020).

f) By end 2020, ECMWF anticipates to have a working version of NEMO + SI3 in mixed precision for DA, medium-range and extended-range ocean prediction in forced and coupled mode. Potential changes will be included into the Mixed-precision branch. (ECMWF+BSC task).

Documentation updates