nxtval-simple.c

The example for Boor USING MPI2

extern int MPE_COUNTER_KEYVAL;
int MPE_Counter_nxtval( MPI_Win counter_win, int *value )
{
    MPI_Group group;
    int       rank, size, myval, flag, i, *val, one = 1;
    MPI_Aint  *myval_p;

    MPI_Win_get_group( counter_win, &group );
    MPI_Group_rank( group, &rank );
    MPI_Group_size( group, &size );
    MPI_Group_free( &group );
    MPI_Win_get_attr( counter_win, MPE_COUNTER_KEYVAL, &myval_p, 
                      &flag );
    myval = *myval_p;

    val = (int *)malloc( size * sizeof(int) );
    MPI_Win_lock( MPI_LOCK_EXCLUSIVE, 0, 0, counter_win );
    for (i=0; i<size; i++) {
	if (i == rank) 
	    MPI_Accumulate( &one, 1, MPI_INT, 0, i, 1, MPI_INT, 
			    MPI_SUM, counter_win );
	else
	    MPI_Get( &val[i], 1, MPI_INT, 0, i, 1, MPI_INT, 
		     counter_win );
    }
    MPI_Win_unlock( 0, counter_win );
    /* Add to our contribution */
    *myval_p = *myval_p + 1;

    /* Compute the overall value.
       Storing *myval_p into val[rank] and starting *value at zero 
       would eliminate the if test */
    *value = myval;
    for (i=0; i<size; i++) {
	if (i != rank) *value = *value + val[i];
    }
    free( val );
    return 0;
}