title: MPI_Comm_split explanation
body: <p>Can someone explain and tell me more about MPI_Comm_split communicator?  </p>
  
  <pre><code>MPI_Comm_split(MPI_COMM_WORLD, my_row, my_rank,&amp;my_row_comm);
  </code></pre>
  
  <p>This is just example i met by reading some basic documentations. Maybe someone could tell me how this  communicator is working? </p>