/******************************************************************************
    Hello World example:

    In this example the rank 0 of MPI_COMM_WORLD waits for messages from the 
    other ranks. When a message is received it is displayed (send to stdout).

    Copyright 2003 (c) Critical Software SA
    . http://www.criticalsoftware.com
    . http://www.criticalsoftware.com/hpc
    . cscsWMPII@criticalsoftware.com

 *****************************************************************************/

#include <mpi.h>
#include <stdio.h>

#define MESSAGELENGTH  128  /* The length of the messages that               */
                            /* we are going to transmit                      */
#define TAG            100  /* The tag to use for the transmissions          */


int main(int argc, char** argv)
{
    int         nCommSize;
    int         nCommRank;
    int         nCounter;
    char        pchMessage[MESSAGELENGTH];
    char    pchNodeName[MPI_MAX_PROCESSOR_NAME];
    int     nNodeNameSize;

    /* Initialize cscsWMPII II:                                                   */
    MPI_Init(&argc, &argv);

    /* Determine what the world looks like and our own position in it:       */
    MPI_Comm_size(MPI_COMM_WORLD, &nCommSize);
    MPI_Comm_rank(MPI_COMM_WORLD, &nCommRank);
    printf ("I am rank %d of %d in MPI_COMM_WORLD\n", nCommRank, nCommSize);

    /* If I am rank 0 I'll receive messages from the other ranks in          */
    /* MPI_COMM_WORLD and send them to stdout:                               */
    if (nCommRank == 0) {
        for (nCounter = 1; nCounter < nCommSize; nCounter++) {
            /* Receive a message from a process:                             */
            MPI_Recv(pchMessage,
                     MESSAGELENGTH,
                     MPI_CHAR,
                     MPI_ANY_SOURCE,
                     TAG,
                     MPI_COMM_WORLD,
                     MPI_STATUS_IGNORE);

            /* Display the received message:                                 */
            printf ("I received the following message: %s\n", pchMessage);
        }
    } else /* I am NOT rank 0 */ {

        /* Get my node name                                                  */
        MPI_Get_processor_name(pchNodeName, &nNodeNameSize);

        /* Compose my message:                                               */
        sprintf(pchMessage,
                "Hello world from rank %d at %s",
                nCommRank,
                pchNodeName);
        /* Send it:                                                          */
        MPI_Send(pchMessage, MESSAGELENGTH, MPI_CHAR, 0, TAG, MPI_COMM_WORLD);
    }

    /* Flush the output so it's shown when using mpiexec                     */
    fflush (stdout);

    /* Pause rank 0 so that the output can be verified:                      */
    if (nCommRank == 0) {
        printf("\nPress ENTER to exit...\n");
        fflush (stdout);
        getchar();
    }

    /* Finalize cscsWMPII II:                                                     */
    MPI_Finalize();
    return 0;
}