Introduction to Hmat-sz

Le descriptif de l’offre ci-dessous est en Anglais_

**Type de contrat **:CDD

**Niveau de diplôme exigé **:Bac + 5 ou équivalent

**Fonction **:Chercheur contractuel

**Niveau d'expérience souhaité **:Jeune diplômé

**A propos du centre ou de la direction fonctionnelle**:
The Inria center at the University of Bordeaux is one of the nine Inria centers in France and has about twenty research teams.. The Inria centre is a major and recognized player in the field of digital sciences. It is at the heart of a rich R&D and innovation ecosystem: highly innovative SMEs, large industrial groups, competitiveness clusters, research and higher education players, laboratories of excellence, technological research institute...

**Contexte et atouts du poste**:
**Industrial context**:
The very strong competitive context in the markets concerned (civil aviation), an increasingly restrictive regulatory framework (standards on acoustic radiation), the search for robustness in calculations (via uncertainty management techniques): all these factors mean that simulation is being used more and more in product development at Airbus. Software tools must be improved to support these uses, while complying with environmental constraints and hardware developments in computing resources.

**Scientific background**:
The increase in available computing power and the widespread use of digital simulation in R&D have led to the emergence of a wide variety of new algorithms (e.g. randomized algorithms based on statistical approaches, those based on learning and AI techniques, mixed arithmetic approaches, hierarchical methods, etc.) in addition to the so-called classical algorithms. If we add to this the choice of data storage format (dense, sparse, compressed, hierarchical, etc.), parallelism (shared and distributed memory), multiple arithmetic methods (single-, double-, half-precision), and heterogeneous computing architectures (CPU, GPU, TPU, etc.), we can see that we are faced with an extremely complex combination if we want to get the very best out of it.

The CONCACE project, jointly run by Airbus, Cerfacs and Inria, proposes to tackle this problem by taking advantage of modern development tools and languages to design high-level expressions of complex parallel algorithms. While the traditional approach to HPC is to fully exploit the hardware, our complementary approach will enable a richer composability of numerical methods, allowing existing and new numerical algorithms to be fully exploited. In this study, we propose to attempt an initial implementation of this methodology in the H-matrix solver (used by the ASERIS and ACTIPOLE software packages mentioned above) for multi-arithmetics and compression.

**Mission confiée**:
**Principales activités**:
**Part 1 : SZ experimentation**:

- the state of the art in this field of activity;
- how SZ positions itself with respect to the other lossy compression methods existing;
- Implement the coupling between SZ and the H-matrix solver, at least in the sequential case;
- How does this impact the accuracy and performance of the H-matrix library;
- What is the computation cost for this new approach.

Deliverable:

- An updated sequential H-Matrix library using SZ (in the github project hmat-oss).

**part 2 : Multi-arithmetics experimentation**:
Multi-arithmetics as proposed in the literature is a new promising way of writing algorithms using all the possible accuracies offered by modern processors in order to maximize performance and minimize storage without impacting accuracy. In the H-matrix solver, we must evaluate the way to implement it in a complex parallel algorithm, and see the impact on computation time and accuracy.

Deliverable:

- A scientific report presenting experimentation of H-matrix with multi-arithmetics ;
- An updated software version of h-matrix.

**Compétences**:

- Training in HPC (High Performance Computing), parallel algorithms and scientific computing;
- Knowledge of linear algebra and solving linear systems (direct and iterative solvers);
- Working knowledge of programming languages and tools used in these disciplines (C, C++, Fortran, Python, Shell, etc.);
- Basic knowledge of finite element approaches and scientific computing in general.

**Avantages**:

- Subsidized meals
- Partial reimbursement of public transport costs
- Leave: 7 weeks of annual leave + 10 extra days off due to RTT (statutory reduction in working hours) + possibility of exceptional leave (sick children, moving home, etc.)
- Possibility of teleworking and flexible organization of working hours
- Professional equipment available (videoconferencing, loan of computer equipment, etc.)
- Social, cultural and sports events and activities
- Access to vocational training
- Social security coverage

**Rémunération**:
The gross monthly salary will be 2100€ (before social security contributions and monthly witholding tax)

**Informations générales**:

- **Thème/Domaine**: Calcul distribué