Parallel implementation of the PHOENIX generalized stellar atmosphere program

We describe the parallel implementation of our generalized stellar atmosphere and non-LTE (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 multiple instruction-multiple data 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.