Many Broadcasts or Reductions

Does your program include many broadcasts or reductions on large messages? Large broadcasts may benefit from increased values of MPI_SHM_BCASTSIZE, and large reductions from increased MPI_SHM_REDUCESIZE. Also, if many different communicators are involved, you may want to increase MPI_SHM_GBPOOLSIZE. In most cases, the default values will provide best performance.