Nyx is a adaptive mesh, N-body/hydro code for cosmological simulation on massively parallel computers. It couples the compressible hydrodynamic equations on a grid with a particle represenation of dark matter.

The major capabilities:

  • 3-dimensional unsplit, 2nd-order hydrodynamics
  • adaptive mesh refinement with subcycling; jumps of 2x and 4x between levels
  • full Poisson gravity (with triply periodic boundary conditions)
  • hybrid parallelization strategy with MPI + X, where X = OpenMP on multicore architectures

and CUDA/HIP/DPC++ on hybrid CPU/GPU architectures.

Nyx uses an Eulerian grid for the hydrodynamics solver and incorporates adaptive mesh refinement (AMR). Our approach to AMR uses a nested hierarchy of logically-rectangular grids with simultaneous refinement in both space and time, utilizing the AMReX library.