/**
\file   mpiExample1.cpp
\brief  MPI programming example #1.
\author george j. grevera, ph.d.

This program is a skeleton of a parallel MPI application using the one
manager/many workers framework.

<pre>
compile:  mpic++ -g  -o mpiExample1.exe mpiExample1.cpp  # debug version
          mpic++ -O3 -o mpiExample1.exe mpiExample1.cpp  # optimized version
          g++ -g -pthread -o mpiExample1.exe mpiExample1.cpp -llammpio  \
              -llammpi++ -llamf77mpi -lmpi -llam -lutil

run    :  lamboot -v    # to start lam mpi
          mpirun -np 4 ./mpiExample1.exe  # run in parallel w/ 4 processes
          lamhalt       @ to stop lam mpi
</pre>
*/
#include  <assert.h>
#include  <mpi.h>
#include  <stdio.h>
#include  <unistd.h>

static char  mpiName[ 1024 ];  ///< host computer name
static int   mpiRank;          ///< number of this process (0..n-1)
static int   mpiSize;          ///< total number of processes (n)
static int   myPID;            ///< process id
//----------------------------------------------------------------------
/** \brief manager code for example 1
 */
static void manager ( void ) {
    printf( "manager: my rank=%d, size=%d, pid=%d. \n",
            mpiRank, mpiSize, myPID );
    /** \todo  insert manager code here. */
}
//----------------------------------------------------------------------
/** \brief worker code for example 1
 */
static void worker ( void ) {
    printf( "worker: my rank=%d, size=%d, pid=%d. \n",
            mpiRank, mpiSize, myPID );
    /** \todo  insert worker code here. */
}
//----------------------------------------------------------------------
/** \brief   main program entry point for example 1.  execution begins here.
    \param   argc count of command line arguments.
    \param   argv array of command line arguments.
    \returns 0 is always returned.
 */
int main ( int argc, char* argv[] ) {  //not const because MPI_Init may change
    if (MPI_Init( &argc, &argv ) != MPI_SUCCESS) {
        //actually, we'll never get here but it is a good idea to check.
        // if MPI_Init fails, mpi will exit with an error message.
        puts( "mpi init failed." );
        return 0;
    }

    //get the name of this computer
    gethostname( mpiName, sizeof( mpiName ) );
    //determine rank
    MPI_Comm_rank( MPI_COMM_WORLD, &mpiRank );
    //determine the total number of processes
    MPI_Comm_size( MPI_COMM_WORLD, &mpiSize );
    //get the process id
    myPID = getpid();
    printf( "mpi initialized.  my rank=%d, size=%d, pid=%d. \n",
            mpiRank, mpiSize, myPID );

    if (mpiSize<2) {
        puts("this example requires at least 1 manager and 1 worker process.");
        MPI_Finalize();
        return 0;
    }

    if (mpiRank==0)    manager();
    else               worker();

    MPI_Finalize();
    return 0;
}
//----------------------------------------------------------------------