Informations générales
Intitulé de l'offre : Post-doctoral or research engineer proposal, ocean model optimisation (M/F) (H/F)
Référence : UMR7159-SEBMAS-002
Nombre de Postes : 1
Lieu de travail : PARIS 05
Date de publication : mercredi 5 mars 2025
Type de contrat : Chercheur en contrat CDD
Durée du contrat : 24 mois
Date d'embauche prévue : 1 avril 2025
Quotité de travail : Complet
Rémunération : The gross salary per month (including national health transport and lunch subsidies, insur- ance and employment insurance) varies from 2600 to 3700 euros depending on the experience.
Niveau d'études souhaité : Doctorat
Expérience souhaitée : Indifférent
Section(s) CN : 06 - Sciences de l'information : fondements de l'informatique, calculs, algorithmes, représentations, exploitations
Missions
The ocean model, NEMO has been designed to run in double precision, i.e. using 64-bit floating-point numbers. Using lower precision can be beneficial in terms of performance by reducing memory usage, execution time (by two) and energy consumption. However, lower precision can also increase numerical instabilities. The main objective of this project is to automatically identify and control sources of instabilities when running NEMO in single precision.
To support this, the plan is to use the CADNA library [1, 2] which relies on Discrete Stochas- tic Arithmetic [3] to estimate rounding errors in numerical codes and detect numerical insta- bilities that may occur during their execution. The CADNA library will be used to control
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the numerical quality of the results computed by NEMO and point out the possible numer- ical instabilities. By leveraging CADNA, we will automatically identify instability sources and try to fix/bypass them by combining our expertise on NEMO algorithms with CADNA developers' knowledge of numerical precision/instabilities. Different physical configurations of NEMO, either local or global, will be studied. We also plan to optimize the threshold values in NEMO, taking into account the various precisions used.
Activités
- Implementation and use of the CADNA library in the NEMO code
- Using CADNA to identify numerical stability problems in NEMO in single precision in a series of simplified test cases
- Resolution of the numerical instabilities identified by modifying the algorithms using a combination of computer/mathematical/physical solutions
- Repetition of the sequence Identification/resolution of numerical instabilities in increasingly complex numerical simulations of the ocean, up to simulations of the global ocean including sea ice.
Compétences
Candidates must have a PhD in Computer Science, Applied Physics, Applied Mathematics or other relevant fields, with both good programming skills and good knowledge in numerical algorithms.
Contexte de travail
Position in the LIP6 laboratory (PEQUAN team: Performance and Quality of Numerical Algorithms) in collaboration with LOCEAN (NEMO R&D team). Both laboratories are located on the Pierre and Marie Curie campus at Sorbonne University.
Contraintes et risques
None