Question

I use MPI library for C and I would like to know is it possible to call the MPI collective communication methods from different parts of code by different processes?

Pseudo Example:

MPI_Rank(&rank,MPI_COMM_WORLD);

switch(rank) {
 case 0:
     MPI_Bcast(buf1,count, type, 0, comm);
     break;
 case 1:
     MPI_Bcast(buf1,count, type, 0, comm);
     break;
 case 2:
     MPI_Bcast(buf1,count, type, 0, comm);
     break;
}

or it must be called from same line of code for every process?

     MPI_Bcast(buf1,count, type, 0, comm);

Sorry for trivial question but I googled it and failed to find the answer.

Thank You !

Answer 1

It can be called from different parts of the code, but you must make sure that all processes in the communicator actually call MPI_Bcast to avoid deadlocking. This might be slightly more difficult to ensure if all processes follow different execution paths.