Minimal Example (Blocking Reconfiguration)

The following C example demonstrates a blocking reconfiguration using the Dyn_PSets library. Copy and adapt for quick experimentation.

int main(){
    MPI_Session session;
    dyn_pset_state_t *dyn_pset_state;
    int terminate, reconfigured = 0;
    char msg[256];

    /* Initialize a Session so we can create MPI_Info objects before dyn_pset_init */
    MPI_Session_init(MPI_INFO_NULL, MPI_ERRORS_ARE_FATAL, &session);

    /* Set DynPSet verbosity and stdout as outputstream
    dyn_pset_set_output(NULL, 0); // Increase to print DynPset debug output */

    /* Initialize the DynPSet state */
    dyn_pset_state = dyn_pset_init("mpi://WORLD", NULL, MPI_INFO_NULL, NULL, NULL, NULL, NULL);

    /* In the general case an expansion might be canceled, so we check for it here */
    if (NULL == dyn_pset_state){
        MPI_Session_finalize(&session);
        return 0;
    }

    /* Code path for dynamically added processes */
    if(dyn_pset_state->dynamic_process){
        /* Receive and print message from existing processes before terminating*/
        MPI_Bcast(msg, 256, MPI_CHAR, 0, dyn_pset_state->mpicomm);
        printf("NEW PROCESS: rank %d/%d received message '%s' from original processes\n",
                                                            dyn_pset_state->mpirank, dyn_pset_state->mpisize, msg);

    /* Code path for original processes */
    }else{

        printf("ORIGINAL PROCESS: == BEFORE reconfiguration: Rank %d/%d\n", dyn_pset_state->mpirank, dyn_pset_state->mpisize);

        /* Set the optimization information for the DynPSet state */
        MPI_Info_create(&info);
        MPI_Info_set(info, "mpi_num_procs_add", "2");
        dyn_pset_set_info(dyn_pset_state, info);
        MPI_Info_free(&info);

        /* Reconfigure the DyPSet state */
        dyn_pset_adapt(dyn_pset_state, &terminate, &reconfigured);

        printf("ORIGINAL PROCESS: == AFTER reconfiguration: Rank %d/%d\n", dyn_pset_state->mpirank, dyn_pset_state->mpisize);

        strcpy(msg, "Hello, new processes!");
        MPI_Bcast(msg, 256, MPI_CHAR, 0, dyn_pset_state->mpicomm);

    }

    /* Finalize the DynPSet state */
    dyn_pset_finalize(&dyn_pset_state, NULL);

    /* Finalize our MPI Session */
    MPI_Session_finalize(&session);

    return 0;
}