Astra code documentation

About Astra

Astra is designed to be a performance-portable code to model astrophysical plasmas with spectral accuracy. This means that it can run both on your laptop’s cpu or on the largest GPU HPCs recently bought by your university. More technically, Astra can run in serial, use OpenMP and/or MPI (message passing interface) for parallelization, and use CUDA or Xeon-Phi for out of chip acceleration. Of course, all these capabilities are embedded within one single code, so the code relies on relatively abstracted classes and objects available in C++20, which are not necessarily familiar to astrophysicists. A large effort has been devoted to simplify this level of abstraction so that the code can be modified by researchers and students familiar with C and who are aware of basic object-oriented concepts.

The algorithms implemented in Astra are based on the Snoopy Code.

Requirements

Astra is written in standard C++20 and does not rely on any external libraries when running in serial (non-MPI mode).

Compiler: Astra requires a C++20 compatible compiler. It has been tested successfully with GCC (>10), Intel compiler suite (>2018) and Clang on both Intel and AMD CPUs. Astra has also been tested on NVIDIA GPUs (Pascal, Volta and Ampere architectures) using the nvcc (>10) compiler, and on AMD GPUs (Radeon Mi50, Mi210, Mi250) using the hipcc compiler.
Kokkos and kokkos-fft libraries: Astra relies internally on the Kokkos and kokkos-fft libraries, which are bundled with Astra as git submodules and compiled on the fly, hence no external installation is required.
FFT Library: Astra requires an external library to compute Fast Fourier Transforms (FFT). Astra has been tested successfully with the FFTW library on CPU architectures, and with the cuFFT and rocFFT libraries on GPU architectures. Note that Astra does not rely on the MPI version of these libraries, so the serial version of the library is sufficient even when using Astra in MPI parallelisation mode.
MPI library: When using MPI parallelisation, Astra relies on an external MPI library. Astra has been tested successfully with OpenMPI and IntelMPI libraries. When used on GPU architectures, Astra assumes that the MPI library is GPU-Aware. If unsure, check this last point with your system administrator.

Features

incompressible hydrodynamics using a pseudo-spectral method in 3D
incompressible magneto-hydrodynamics using a pseudo-spectral method in 3D

Terms and condition of Use

Astra is distributed freely under the CeCILL license, a free software license adapted to both international and French legal matters, in the spirit of and retaining compatibility with the GNU General Public License (GPL).

Astra also relies on the Kokkos performance portability programming ecosystem released under the terms of Contract DE-NA0003525 with National Technology & Engineering Solutions of Sandia, LLC (NTESS).

Main Contributors

Geoffroy Lesur: code design and architecture, implementation of the main algorithms, documentation and testing.

Astra has also been inspired by all of the contributors of the Idefix code, from which the general framework has been derived.

About this documentation

This documentation has automatically been generated on Jun 25, 2026 from the following Astra commit:

Branch:: master
Commit:: ba4f15730f

Acknowledgements

Astra developement team is partly funded by the PEPR Origins through the project “MHD@Exascale”. The Astra collaboration benefited from funding from the “Programme National de Physique Stellaire” (PNPS), “Programme National Soleil-Terre” (PNST), “Programme National de Hautes Energies” (PNHE) and “Programme National de Planétologie” (PNP) of CNRS/INSU co-funded by CEA and CNES.