A Parallel Cosmological Hydrodynamics Code

Understanding the formation by gravitational collapse of galaxies and the large-scale structure of the universe is a nonlinear, multi-scale, multi-component problem. This complex process involves dynamics of the gaseous baryons as well as of the gravitationally dominant dark matter. We discuss an implementation of a parallel, distributed memory, cosmological hydrodynamics code using MPI message passing; it is based on the Total-Variation-Diminishing (Harten 1983) serial code of Ryu et al. (1993). this parallel code follows the motion of gas and dark matter simultaneously, combining a mesh based Eulerian hydrodynamics code and a Particle-Mesh N-body code. A new, flexible matrix transpose algorithm is used to interchange distributed and local dimensions of the mesh. Timing results from runs on an IBM SP2 supercomputer are given.