Thornado-mini is a proxy app developed in the ExaStar ECP AD project. The ExaStar project targets multi-physics simulations of astrophysical explosions. Their target application, Clash, will be a component-based multi-physics toolkit, built on capabilities of current astrophysics simulation codes Flash and Castro and on the massively parallel adaptive mesh refinement framework {AMReX}. The Clash code suite will have modules for hydrodynamics, advanced radiation-transport, thermonuclear kinetics, and nuclear microphysics. In this code suite, the radiation transport kernel is expected to consume 80\% of the full application runtime.

Thornado-mini is a proxy app for finite element, moment-based radiation transport. The proxy application code is a serial code written in Fortran 90 that solves the equation of radiative transfer using a semi-implicit, discontinuous Galerkin (DG) method for the two-moment model of radiation transport. Thornado-mini currently implements deleptonization from electron capture on nucleons and nuclei using tabulated neutrino opacities provided by the WeakLib library.
The deleptonization problem is representative of both the flops and memory access patterns that are expected in the exascale problem.