title: How to know the all the ranks of the processor that are part of a communicator in MPI?
body: <p>Is there anyway through which I can know all the processes that are part of communicator? 
  Suppose there are totally 16 MPI processes and MPI_Comm comm has 4 processes as a group. Given  just the communicator comm can we know all the ranks of the processes that are part of the communicator? </p>
  
  <p>Thank You</p>