/*
 * Copyright 1998-2001, University of Notre Dame.
 * Authors: Jeffrey M. Squyres, Arun Rodrigues, and Brian Barrett with
 *          Kinis L. Meyer, M. D. McNally, and Andrew Lumsdaine
 * 
 * This file is part of the Notre Dame LAM implementation of MPI.
 * 
 * You should have received a copy of the License Agreement for the Notre
 * Dame LAM implementation of MPI along with the software; see the file
 * LICENSE.  If not, contact Office of Research, University of Notre
 * Dame, Notre Dame, IN 46556.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted subject to the conditions specified in the
 * LICENSE file.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Additional copyrights may follow.
 * 
 *
 *	University of Notre Dame LAM
 *	$Id: ezstart.c,v 6.5 2000/10/31 05:23:35 jsquyres Exp $
 *
 *  NOTE: This example has unneccesary use of printf.  They are only
 *        to give the new user some feedback.
 *
 */


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

#define WORKTAG		1
#define DIETAG		2
#define NUM_WORK_REQS	100

/*
 * Local functions
 */
static void		master(void);
static void		slave(void);


/*
 * main
 * This program is really MIMD, bit is written SPMD for
 * simplicity in launching the application.
 */
int
main(int argc, char* argv[])
{
	int		myrank;

	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD,	/* group of everybody */
			&myrank);	/* 0 thru N-1 */

	if (myrank == 0) {
		master();
	} else {
		slave();
	}

	MPI_Finalize();
	return(0);
}

/*
 * master
 * The master process sends work requests to the slaves
 * and collects results.
 */
static void
master(void)
{
	int		ntasks, rank, work;
	double		result;
	MPI_Status	status;

	MPI_Comm_size(MPI_COMM_WORLD,
			&ntasks);	/* #processes in app */
/*
 * Seed the slaves.
 */
	work = NUM_WORK_REQS;		/* simulated work */

        printf("Master started.\n\n");

	for (rank = 1; rank < ntasks; ++rank) {

		MPI_Send(&work,		/* message buffer */
			1,		/* one data item */
			MPI_INT,	/* of this type */
			rank,		/* to this rank */
			WORKTAG,	/* a work message */
			MPI_COMM_WORLD);/* always use this */
		work--;

		printf("Seeding Machine %d.\n\n",rank);

 	}
/*
 * Receive a result from any slave and dispatch a new work
 * request until work requests have been exhausted.
 */
	while (work > 0) {

		MPI_Recv(&result,	/* message buffer */
			1,		/* one data item */
			MPI_DOUBLE,	/* of this type */
			MPI_ANY_SOURCE,	/* from anybody */
			MPI_ANY_TAG,	/* any message */
			MPI_COMM_WORLD,	/* communicator */
			&status);	/* recv'd msg info */

		MPI_Send(&work, 1, MPI_INT, status.MPI_SOURCE,
				WORKTAG, MPI_COMM_WORLD);

		work--;			/* simulated work */

		printf("Feeding machine %d.\n\n",status.MPI_SOURCE);
	}
/*
 * Receive results for outstanding work requests.
 */

	printf("Receiving outstanding work.\n\n");

	for (rank = 1; rank < ntasks; ++rank) {
		MPI_Recv(&result, 1, MPI_DOUBLE, MPI_ANY_SOURCE,
				MPI_ANY_TAG, MPI_COMM_WORLD, &status);
	}
/*
 * Tell all the slaves to exit.
 */
	for (rank = 1; rank < ntasks; ++rank) {
		MPI_Send(0, 0, MPI_INT, rank, DIETAG, MPI_COMM_WORLD);
	}


	printf("Master exiting.\n\n");

}

/*
 * slave
 * Each slave process accepts work requests and returns
 * results until a special termination request is received.
 */
static void
slave(void)
{
	double		result;
	int		work;
	MPI_Status	status;

	for (;;) {
		MPI_Recv(&work, 1, MPI_INT, 0, MPI_ANY_TAG,
				MPI_COMM_WORLD, &status);
/*
 * Check the tag of the received message.
 */
		if (status.MPI_TAG == DIETAG) {
			return;
		}

		sleep(1);
		result = 6.0;		/* simulated result */

		MPI_Send(&result, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD);
	}
}