Subject

The AMITEX code developed by CEA is a massively parallel code (distributed memory), using Discrete Fourier Transforms, for the numerical simulation of the mechanical behavior of heterogeneous materials. It overcomes the limitations (in size and computation time) encountered by standard finite-element codes used in the same context. A stabilized version of the code, available to the public at https://amitexfftp.github.io/AMITEX/, is used by various national (Mines Paris, ONERA, ENSTA Bretagne, I2M-ENSAM Bordeaux, Météo-France, etc.) and international (USA, UK, China, Canada, Germany, Finland, Poland, etc.) teams.

The aim of the post-doc, proposed over two years, is threefold: to extend the field of application of the AMITEX code to non-periodic boundary conditions, to explore a possible adaptation to hybrid CPU/GPU architectures, and to use these extensions to develop FFT-based multi-scale couplings. This objective is built around the 2decomp open source library, on which AMITEX is based, and whose development was taken over in 2022 (https://github.com/2decomp-fft/2decomp-fft)[1] by a French-English team. 

The various tasks of the post-doc consist of :

– extend the functionalities of the AMITEX code (non-periodic BC) by introducing different types of discrete transforms (sine, cosine, Fourier) within the 2decomp library,

– explore 2decomp‘s current development towards the use of hybrid CPU/GPU architectures, with the aim of setting up a first AMITEX-GPU code,

– use this new functionality for multi-scale coupling, where a local (refined) simulation interacts with a global (unrefined) simulation [3] via non-periodic boundary conditions,

[1] Rolfo, S.; Flageul, C.; Bartholomew, P.; Spiga, F. & Laizet, S. The 2DECOMP&FFT library: an update with new CPU/GPU capabilities, Journal of Open Source Software, The Open Journal, 2023, 8, 5813

[2] Gélébart L., FFT-based simulations of heterogeneous conducting materials with combined nonuniform Neumann, Periodic and Dirichlet boundary conditions, Eur. Jour. Mech./A solids, Vol. 105, 2024

[3] Noé Brice Nkoumbou Kaptchouang and Lionel Gélébart. Multiscale coupling of fft-based simulations with the ldc approach. Computer Methods in Applied Mechanics and Engineering, 3

Candidate and subject

– The candidate should have completed his/her thesis in the field of numerical mechanics and have a strong and practical interest for computer development, particularly through open source codes (2decomp and AMITEX),

– Although the subject is aimed at (numerical) solid mechanicians, it may also be suitable for (numerical) fluid mechanicians or physicians who wish to open up to solid mechanics,

– Part of the topic concerns extension to GPUs, so prior knowledge of GPU programming will be a plus. However, this point is not essential if the candidate demonstrates solid computer skills that will enable him or her to be trained quickly,

– Depending on the candidate’s professional project and/or initial skills, the part of the work on multi-scale coupling, which will enable the project to be promoted through scientific publications, could be strengthened and/or extended to other types of coupling, and especially multi-physics couplings.

Details

The post-doc, based at CEA Saclay and granted for 2 years, will draw on the skills of L. Gélébart (DES/ISAS/DRMP/SRMA), developer of the AMITEX code, Y. Wang, HPC simulation specialist at the Maison de la Simulation (DRF) and Cédric Flageul (co-developer of the 2decomp library) from the University of Poitiers.

Contacts 

lionel.gelebart@cea.fr

yushan.wang@cea.fr

cedric.flageul@univ-poitiers.fr

Overview

Maison de la Simulation offers 2-3 engineer positions to join the newly created PDI team.

• Contact: Yushan Wang (yushan.wang@cea.fr) & Benoît Martin (bmartin@cea.fr)
• Duration: 3 years
• Start date: ASAP

Application

Candidates must have at least a Master’s degree or equivalent in Computer Science, Applied Mathematics, or other relevant fields. A PhD degree and working experience in a relevant domain are appreciated. Good programming skills are required.

Applications should be sent to Yushan Wang and Benoît Martin. They should include:

• a curriculum vitae
• a motivation letter
• at least two referees with their email addresses
• links to Masters/PhD thesis and publications
• links to software contributions

Context

With the increasing complexity of numerical simulation codes, new approaches are required to analyze the ever-growing amount of data. This requires coupling up-to-date data analysis libraries with the existing highly optimized numerical simulation codes. The PDI Data Interface code coupling library is designed to fulfill this goal.

The open-source PDI Data Interface library is designed and developed for process-local loose coupling in high-performance simulation codes. PDI supports the modularization of codes by inter-mediating data exchange between the main simulation code and independent modules (plugins) based on various libraries. It is developed in modern C++ and offers C, Fortran, and Python application programming interfaces.

PDI offers a reference system similar to Python or C++’s shared_ptr with locking to ensure coherent access by coupled modules. It provides a global namespace (the data store) to share references and implements the Observer pattern to enable modules to react to data availability and modifications. It implements a metadata system that can specify a dynamic type for references based on the value of other data (e.g., array size based on the value of a shared integer). Codes using PDI’s declarative API expose the buffers in which they store data and trigger notifications when significant steps in the simulation are reached. Third-party libraries such as HDF5, SIONlib, or FTI are wrapped in a PDI plugin. A YAML configuration file is used to interleave plugins and additional code without modifying the original application.

Another aspect we explore with PDI is in-situ data analysis, which performs numerical analytics during the simulation. This is necessary due to the ever-growing gap between file system bandwidth and compute capacities. To this end, we are developing the Deisa plugin. This plugin is based on the open-source Dask framework and allows us to transfer data to dedicated processes to perform in-situ analysis.

One of our goals is to establish a feedback mechanism between the in-situ data analysis and the numerical simulation. This allows better resource allocations and on-the-fly simulation monitoring. Another aspect that in-situ analysis enables is using AI methods for HPC and HPDA. For instance, we can have unsupervised detection of rare events during the simulation, which can greatly reduce the amount of produced data, thus reducing stress on the file system.

Work environment

At Maison de la Simulation laboratory, you will join a group of engineers and scientists focusing on all aspects of high-performance computing (HPC). You will have the opportunity to collaborate with PDI users and to introduce new features in the PDI plugin family. As a member of the PDI team, you will also have the opportunity to exchange with the developers of other HPC codes to enrich your skills in HPC code development. To validate your developments, you will be provided with access to the top European supercomputers (Adastra, Jean-Zay, etc.).

Work content

As a member of the newly created PDI team, your primary focus will be developing and maintaining the PDI library.

• Develop core functionalities and new plugins for PDI
• Develop the Deisa library
• User-support
• Organize training sessions
• Library packaging and deployment

Skills

The successful candidate will master the following skills and knowledge:

• Proficiency in modern C++ (C++14 and above)
• Software engineering and library design
• Modern development environment (Linux, git, CMake, etc.)
• Communication (writing, presenting, and training)
• Team-work and integration in an international environment

In addition, the following will be considered a plus:

• Data analysis libraries such as Dask
• Knowledge and experience with Python, Fortran and/or GPU computing
• HPC and parallel libraries such as OpenMP and MPI
• HPC parallel IO libraries such as HDF5 or NetCDF
• Experience with supercomputer tools (slurm, sbatch, etc), packaging and deployment

Salary and benefits

The CEA offers salaries based on your degrees and experience. This position offers several advantages:

• The possibility of joining collaborations with other European laboratories, the United States, and Japan
• Numerous opportunities to travel internationally (exchanges, conferences, workshops and more)
• 5 weeks of paid vacation and 4 weeks of RTT per year, and up to 2 days of remote work per week
• Reimbursement of up to 75% of public transport cards and a free transport network throughout the Ile-de-France region
• Complimentary health insurance and several company savings plans

References

• Maison de la Simulation: https://mdls.fr/
• PDI: https://pdi.dev/
• Deisa: https://github.com/pdidev/deisa

Join the CEA’s ambitious “Moonshot” project, CExA, and contribute to the development of the Kokkos GPU computing library. We are recruiting six talented and enthusiastic C++ development engineers for a period of 2 years to work at our CEA Saclay site near Paris.

To apply, please send your application (resume and cover letter) to contact@cexa-project.org. You can use this same address for any questions concerning the offer. Applications will be evaluated from mid-May until the position is filled.

Context

Europe is investing to build exaflop supercomputers in the coming years, including one in France, at the CEA, in 2025. These machines will be heterogeneous, accelerated by GPUs of various brands and architectures. Ensuring performance and portability under these conditions is certainly one of the greatest challenges of the Exascale. To address it, CEA is investing heavily in an ambitious “Moonshot” project: CExA. In this project, we will setup libraries to fully exploit this computing power in the scientific applications of the CEA by contributing, extending and adapting the open-source library Kokkos. Within CExA, we represent teams with expertise in numerical computation from the four components of the CEA.

• Maison de la Simulation of the DRF is a joint research and engineering laboratory of CEA, CNRS, Univ. Paris-Saclay and UVSQ specialized in high performance computing and numerical simulation.
• The DES’s software engineering department for simulation brings together three laboratories that address the issues of simulation environment, AI and data science, high performance computing and numerical analysis.
• The DSCIN at DRT/LIST is responsible for the research and development of digital integrated circuits and processors for AI, as well as the design of complex digital architectures. It also works on solutions for embedded systems and develops design tools for embedded AI, embedded systems and trusted circuits.
• The DSSI of the DAM manages activities in the fields of computer science, applied mathematics and information systems, covering a wide spectrum from definition and design to user services.

Mission

As part of a new agile team being set up to carry out the CExA project, you will work in collaboration with the European HPC ecosystem and the teams in charge of the development of Kokkos in the United States (Sandia and Oakridge National labs). You will enrich the library to fit the needs of the CEA applications and to the technologies developed by Europe for the Exascale (EPI, SiPearl, RISC-V).  You will work with cutting-edge and experimental hardware technologies from major vendors (NVIDIA, AMD, INTEL, ARM) that will equipped forthcoming super-computers.

Your mission will include:

• Agile development in C++ of the CExA middleware to address the following areas of improvement:
  • Adaptation to “distributed memory” architectures
  • Support for heterogeneous architectures for European exaflop supercomputers
  • Interfacing with external libraries and data processing tools
  • Simplification of deployment

• Porting via Kokkos and integration of new functionalities in selected application demonstrators (hydrodynamics, fusion energy, AI-assisted medicine)
• Support and animation on parallel programming models within the laboratory and at the scale of European and global collaborations.

Skills

You have a master and/or an engineering degree in computer science and:

• You have a solid knowledge of advanced C++ and the latest standards.
• You know how to fit into an agile development process (SCRUM) and you master the basic tools associated with collaborative development (git, github, etc.).
• You have skills in software engineering. You are familiar with common development environments and associated tools (cmake, docker, spack, gtest, ctest, etc.).
• Knowledge of parallel programming (GPU, multi-threaded, etc.) is a plus, especially with the Kokkos library or equivalent.
• You are autonomous and you wish to be part of an international work team. You master technical English (written and oral). You are interested in the world of high-performance computing and its challenges and follow the evolution of technologies.

Salary and benefits

The CEA offers salaries based on your degrees and experience.

This position offers several advantages:

• the possibility to join collaborations with other European laboratories, the United States and Japan,
• Numerous opportunities to travel internationally (exchanges, conferences, workshops and more)
• Up to 3 days of telecommuting per week
• Reimbursement of up to 75% of public transport cards and a free transport network throughout the Ile-de-France region,
• An interesting complementary health insurance and several company savings plans,
• 5 weeks of paid vacation and 4 weeks of RTT per year.

Contact

FAUCHER Vincent CEA DES/DTN/DIR (See pdf)

Background

Taking into account multiple and coupled physics is at the heart of many application needs in fields as varied as, but not limited to, aeronautics, defense and biology. This is also strong area of expertise for CEA’s Energy Division, with multiple domains including fluid-structure interaction, neutronics coupled with thermal-hydraulics a/o thermal-mechanics or severe accident modeling. The emergence of exascale architectures opens the way to promising new levels of high-fidelity simulations, but is also significantly increasing the complexity of many software applications in terms of total or partial rewriting. It therefore specifically encourages coupling to limit development work. The idea is to search for each physics of interest in a necessarily reduced number of highly optimized software components, rather than making specific, possibly redundant developments in standalone applications.
Once the coupled multiphysics problem has been written with the expected levels of accurracy and stability, the proposed work concentrates on the resolution algorithms to enable the coupling between applications asssumed to be themselves exascale-compatible, to be solved efficiently at exascale. It is also worth noting that, in general, the couplings under consideration can present a high level of complexity, involving numerous physics with different level of feedback between them and various communications from border exchanges to overlaping domains. The current post-doctoral internship to be carried out in the framework of the ExaMA collaborative project, is in particular dedicated to the identification and dynamic tuning of the relevant numerical parameters arising from the coupling algorithms and impacting the computational efficiency of the global simulation. Considered problems are in the general case time-evolving problems, with a significant number of time iterations allowing using the first iterations to gather data and conduct the tuning.

Background

This PostDoc will be carried out in the framework of the PEPR (Programme et Equipement Prioritaire de Recherche) NumPEx project devoted to High Performance Numerics for the Exascale and financed by the France2030 investment program.

Research directions

During this PostDoc several directions will be explored to improve algorithms for precision auto-tuning and numerical validation.

We plan to design a novel autotuning algorithm that will automatically provide arbitrary precision codes, from a required accuracy on the computed results. Because of the number of possible type configurations, particular attention will be paid to the algorithm performance. The type configuration produced will then enable one to improve storage cost, and also execution time taking into account the numerical formats available on the target architectures.

We plan to combine mixed precision algorithms and precision autotuning tools. Such automatic tools may be useful in the design of mixed precision linear algebra algorithms. Conversely the performance of precision autotuning tools may be improved thanks to mixed precision algorithms. Linear algebra kernels could be automatically identified in simulation codes, and replaced by their mixed precision version, in order to reduce the exploration space for precision tuning.

The precision auto-tuning algorithms designed during this PostDoc will be validated on large scale programs developed by partners of the NumPEx project. Furthermore new methodologies will be proposed to perform autotuning of both numerical formats and performance parameters in collaboration with experts in coupled physics simulations.

Location

Sorbonne Université and its Computer Science lab LIP6 are settled on the Pierre & Marie Curie Campus in the Latin Quarter of Paris, France.

Salary

The gross salary per month (including national health insurance and employment insurance) varies from 2682 to 3701 euros depending on the experience.

Duration

1 year, renewable 1 year

Qualifications and skills

Candidates must have a PhD in Computer Science, Applied Mathematics or other relevant fields, with good programming skills. Developments will be carried out in C++ and Python, so programming expertise in at least one of these languages is required. Good knowledge in numerical algorithms and floating-point computation is also required.

CEA is recruiting DevOps engineers for a 2-year period to join the CExA “Moonshot” project team, which is setting up CEA’s GPU computing software stack around the Kokkos C++ library, to contribute to innovative packaging, deployment and continuous integration approaches for supercomputers, based in particular on Spack. A team of more than 10 people is currently being set up. The positions will be based at the CEA Saclay site near Paris.

To apply, please send your application (CV and covering letter) to contact@cexa-project.org. If you have any questions about the position, please use the same address. Applications will be assessed from mid-November until the position is filled.

Context

Europe is preparing for the arrival of the first exascale supercomputers, including one in France, at the CEA, from 2025. These machines will be heterogeneous, accelerated by GPUs of various vendors and architectures. Ensuring performance and portability under these conditions is undoubtedly one of the greatest challenges of Exascale. To address this, the CEA is investing heavily in an ambitious ‘Moonshot’ project: CExA. In this project, we will be providing the libraries needed to fully exploit this computing power in CEA’s scientific applications by contributing to, extending and adapting the Kokkos open-source library. The software stack created in this way will be deployed on the supercomputers using the Spack tool, which has been specially designed for supercomputing environments. Within CExA, we represent teams with expertise in numerical computation from the CEA’s four divisions.

• Maison de la Simulation (https://www.mdls.fr) of Fundamental Research division the is a joint research and engineering laboratory of the CEA, CNRS, Paris-Saclay University and Versailles Saint Quentin University specializing in high-performance computing and numerical simulation.
• The software engineering department for simulation of the Energy Research Division groups together three laboratories that address the issues of simulation environments, AI and data science, intensive computing and numerical analysis.
• LIST’s DSCIN at Technological Research Department is responsible for the research and development of digital integrated circuits and processors for AI, as well as the design of complex digital architectures. It also works on solutions for embedded systems and develops design tools for embedded AI, embedded systems and trusted circuits.
• The DSSI at Military Application Department manages and carries out activities in the fields of computing, applied mathematics and information systems, covering a broad spectrum from definition and design to user services.

Mission

As part of a new agile team being set up to carry out the CExA project, you will be working in collaboration with the French (in particular NumPEx) and European HPC ecosystem and with the teams in charge of developing Kokkos and Spack in the United States to adapt the tools to the needs of the applications developed by the CEA and to the technologies developed by Europe for Exascale (EPI, SiPearl, RISC-V).

Your mission will include:

• Supporting agile development in C++ around Kokkos by contributing to the following points:

• Implementing a testing and performance measurement strategy.
  • Designing, automating and administering continuous integration pipelines.
  • Working with development teams to optimize packaging and deployment processes.
  • Assist with deployment on heterogeneous architectures for European exaflop supercomputers.

• Identify and participate in the development of missing functionalities within the tools used for packaging and deployment and continuous integration.
• Helping to deploy Kokkos in the software environments of selected application demonstrators (hydrodynamics, fusion energy, etc.).
• Provide support and leadership on these themes within the organization and on the scale of European and global collaborations.

Skills

You have a Master’s degree and/or an engineering degree in computer science and:

• You will be able to work within an agile development process (SCRUM) and be familiar with the basic tools associated with collaborative development (Git, GitHub, etc.).
• You have software engineering skills. You are familiar with common development environments and associated tools (CMake, Docker, Spack, GoogleTest, CTest, etc.).
• Scripting skills (Python, Shell, etc.)
• Any knowledge of parallel programming (GPU, multi-threading, etc.) is a plus, particularly with the Kokkos library or equivalent.
• You have knowledge of the C++ ecosystem.
• You are a self-starter and are keen to join an international team. You have a good command of technical English (written and spoken). You are interested in the world of high-performance computing and its challenges and keep updated with the latest technological evolution.

Salary and benefits

The CEA offers competitive salaries depending on your qualifications and experience.

There are several advantages to this position:

• The possibility of joining existing collaborations with other laboratories in Europe, the United States and Japan,
• Numerous opportunities for international travel (exchanges, conferences, workshops and more),
• Up to 3 days’ teleworking per week,
• 75% reimbursement on public transport and a free transport network throughout the Ile-de-France region,
• An attractive supplementary pension scheme and several company savings plans,
• 5 weeks’ paid holiday and 4 weeks’ RTT per year.