Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program

We describe the parallel implementation of our generalized stellar atmosphere and NLTE radiative transfer computer program PHOENIX. We discuss the parallel algorithms we have developed for radiative transfer, spectral line opacity, and NLTE opacity and rate calculations. Our implementation uses a MIMD design based on a relatively small number of MPI library calls. We report the results of test calculations on a number of different parallel computers and discuss the results of scalability tests. -- 3 -- 1. Introduction Much of the astrophysical information that we possess has been obtained via spectroscopy. Spectroscopy of astrophysical objects allows us to ascertain velocities, temperatures, abundances, sizes, and luminosities of astrophysical objects. Much can be learned from some objects just by examining line ratios and redshifts, but to really understand an observed spectrum in detail often requires detailed fits to synthetic spectra. Detailed synthetic spectra also serve to test..