Hydrodynamical simulations of the universe

Simulating the universe using an N-body code involves using N mass points to trace the evolution of structure as it evolves from some specified set of initial perturbations. One of the major advantages of using CRAFT is that the parallel code is immediately portable to a workstation. Load balancing is crucial for an efficient parallel code. Placing refinements in parallel is very difficult. Refinements are placed by examining the numbers of particles in each of the PP boxes. The processors are linked together with high-speed interconnections so that interprocessor communication is very fast. Hydra is the endpoint of several stages of code development. It is extremely fast when the particles are unclustered. A parallel adaptive grid code based on Couchman's algorithm has been implemented on the Cray T3D using CRAFT. Identical code can be run on a workstation by using a preprocessor directive. This makes testing of the code very easy as local workstations can be used. The code has been used successfully to run 16.7-million-particle dark matter and 4.2-million-particle mixed dark matter and gas cosmological simulations.