Overview of process groups

Process Groups

• A group is a set of N processes
  • these processes are uniquely labelled by the integers
  • the integer that labels a process is called its rank within the group.
• A group is represented by an opaque object
  • user does not know internal structure
  • must call inquiry routine to determine attributes
  • referenced by means of a handle
  call mpi_group_size (group, size, ierr)

  call mpi_group_rank (group, rank, ierr)

• Initially, all processes are members of the group given by the pre-defined communicator MPI_COMM_WORLD