Digital for Exascale

By unifying workflows and automating key stages of the HPC software lifecycle, the Exa-MA framework contributes to more reliable, portable and efficient application deployment on national and EuroHPC systems.

HPC applications require reproducibility, portability and large-scale testing, but the transition from code to computer remains lengthy and heterogeneous depending on the site. The objective is to unify the Exa-MA application framework and automate builds, tests and deployments in accordance with NumPEx guidelines.

An Exa-MA application framework has been set up, integrating the management of templates, metadata and verification and validation (V&V) procedures. At the same time, a complete HPC CI/CD chain has been deployed, combining Spack, Apptainer/Singularity and automated submission via ReFrame/SLURM orchestrated by GitHub Actions. This infrastructure operates seamlessly on French national computers and EuroHPC platforms, with end-to-end automation of critical steps.

In the first use cases, the time between code validation and large-scale execution has been reduced from several days to less than 24 hours, without any manual intervention on site. Performance is now monitored by non-regression tests (high/low scalability) and will soon be enhanced by profiling artefacts.

The approach deployed is revolutionising the integration of Exa-MA applications, accelerating onboarding and ensuring controlled quality through automated testing and complete traceability.

The next phase of the project involves putting Exa-MA applications online and deploying a performance dashboard.

Figure: Benchmarking website page with views by application, by machine, and by use case.
© PEPR NumPEx

How can we model an entire city to better understand its energy, airflow, and heat dynamics? Urban data are abundant — buildings, roads, terrain, vegetation — but often inconsistent or incomplete. A new GIS–meshing pipeline now makes it possible to automatically generate watertight, simulation-ready city models, enabling realistic energy and microclimate simulations at the urban scale.

Urban energy/wind/heat modeling requires closed and consistent geometries, while the available data (buildings, roads, terrain, hydrography, vegetation) are heterogeneous and often non-watertight. The objective is therefore to reconstruct watertight urban meshes at LoD-0/1, interoperable and enriched with physical attributes and models.

A GIS–meshing pipeline has been developed to automate the generation of closed urban models. It integrates data ingestion via Mapbox, robust geometric operations using Ktirio-Geom (based on CGAL), as well as multi-layer booleans ensuring the topological closure of the scenes. Urban areas covering several square kilometers are thus converted into consistent solid LoD-1/2 models (buildings, roads, terrain, rivers, vegetation). The model preparation time is reduced from several weeks to a few minutes, with a significant gain in numerical stability.

The outputs are interoperable with the Urban Building Model (Ktirio-UBM) and compatible with energy and CFD solvers.

This development enables rapid access to realistic urban cases, usable for energy and microclimatic simulations, while promoting the sharing of datasets within the Hidalgo² Centre of Excellence ecosystem.
The next step is to publish reference datasets — watertight models and associated scripts — on the CKAN platform (n.hidalgo2.eu). These works open the way to coupling between CFD and energy simulation, and to the creation of tools dedicated to the study and reduction of urban heat islands.

Figures: Reconstruction of the city of Grenoble within a 5 km radius, including the road network, rivers and bodies of water. Vegetation has not been included in order to reduce the size of the mesh, which here consists of approximately 6 million triangles — a figure that would at least double if vegetation were included.
© PEPR NumPEx