hw.c

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

#ifdef DEBUG
	#define dbg 
#else 
	#define dbg if(0)
#endif /* DEBUG */

// compile with 
// mpicc hw.c -o hw.out
//
// run with 
// mpirun -np 4 hw.out

#define from_0_to_1 0x12
#define from_1_to_0 0x15

#define player_body_3(self, enemy, TAG1, TAG2) \
	MPI_Recv(buff, msg_size, MPI_CHAR, enemy, TAG2, MPI_COMM_WORLD, &stat);		\
	dbg printf("Iteration: %d\tplayer %d, message recived, my commandor\n", i, self);	\
	MPI_Send(buff, msg_size, MPI_CHAR, enemy, TAG1, MPI_COMM_WORLD);			\
	dbg printf("Iteration: %d\tplayer %d, message sent, my commandor\n",i, self);	\
/* player_body_3 */

#define player_body(self, enemy) \
	player_body_3(self, enemy, tagit(self, enemy), tagit(enemy, self))
/* player_body */

#define tagit(id1, id2) \
	from_##id1##_to_##id2
/* tagit */


int main(int argc, char * argv[])
{
	int numtasks, rank, res;
	int i = 0;
	MPI_Status stat;
	
	// Initialize the parallel stuff	
	res = MPI_Init(&argc, &argv);
	if (res != MPI_SUCCESS) {
		printf("MPI Initialization faild!\n");
		MPI_Abort(MPI_COMM_WORLD, res);
	}

	// Get the info about the parallel stuff
	MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);

	// Check the call accuracy and show the quick help
	if (argc < 4 && rank == 0) {
		printf("\
Usage: %s <n> <size> <mes>\n\
	where:\n\
	<h>	number of messages between threads\n\
	<size>	size in bytes of the message\n\
	<mes>	message to send, needs to fit into the <size> of bytes\n\
", 
		argv[0]);
		MPI_Abort(MPI_COMM_WORLD, res);
	}

	// initialize parameters from the command line
	const char * message = argv[3];
	const int game_num = atoi(argv[1]);
	const int msg_size = atoi(argv[2]);

	char * buff = (char*) malloc(msg_size);

	// Zero player starts the game
	if (rank == 0) {
		for (i = 0; message[i] && i < msg_size; ++i)
			buff[i] = message[i];
		buff[i] = message[i];
		MPI_Send(buff, msg_size, MPI_CHAR, 1, from_0_to_1, MPI_COMM_WORLD);
		printf("player %d, game started, my commandor\n", 0);
	}

	// LET THE GAMES BEGIN
	// umm... 'continue' will be more correct...
	for (i = 0; i < game_num; ++i) {
		if (rank == 0) {
			player_body(0, 1);
		} else if (rank == 1) {
			player_body(1, 0);
		} else if (i == 0) {
			// just introduce the spectators once
			printf("I am %d, and a am a spectator\n", rank);
		}
	}
	// And zero player finishs the game
	if (rank == 1) {
		MPI_Recv(buff, msg_size, MPI_CHAR, 0, from_0_to_1, MPI_COMM_WORLD, &stat);
		if (msg_size == 0) {
			printf("player %d, game finished, my commandor, without message\n", 1);
			
		} else {
			printf("player %d, game finished, my commandor, got %s\n", 1, buff);
		}
	}
	MPI_Finalize();
	return 0;
}