Behavior of MPI_Send and MPI_Recv

Question

Why these lines of code:

if(my_rank != 0) {
    sprintf(msg, \"Hello from %d of %d...\", my_rank, comm_sz);
    if(my_rank == 2) {
        sleep(2);
        spri         


        

Answer 1

strlen() does not include the null terminator, hence it will not be sent to the master. Receiving the message from rank 3 will not overwrite the later part of the string, so it is still displayed. You should use strlen(msg) + 1 as send count.