NAS experiences of porting CM Fortran codes to HPF on IBM SP2 and SGI Power Challenge

Current Connection Machine (CM) Fortran codes developed for the CM-2 and the CM-5 represent an important class of parallel applications. Several users have employed CM Fortran codes in the production mode on the CM-2 and the CM-5 for the last five to six years, constituting a heavy investment in terms of cost and time. With Thinking Machines Corporation's decision to withdraw from the hardware business and with the decommissioning of many CM-2 and CM-5 machines, the best way to protect the substantial investment in CM Fortran codes is to port the codes to High Performance Fortran (HPF) on highly parallel systems. HPF is very similar to CM Fortran and thus represents a natural transition. The Numerical Aerodynamic Simulation (NAS) Program, located at NASA Ames Research Center, is a pathfinder in high-performance computing for NASA and is dedicated to advancing the science of computational aerodynamics. Their experiences with the conversion issues involved in porting CM Fortran codes on the CM-5 to HPF are presented. Several CM Fortran codes have been ported to Subset HPF on the IBM SP2 and the SGI Power Challenge. Speedup ratios versus number of processors for the linear solver and DSMC (direct simulation Monte Carlo) code are presented.