send_recv_ord.c

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

#define MESSAGE_CAPACITY 2048

int main(int argc, char *argv[])
{
	MPI_Init(&argc, &argv);
	
	int my_rank = -1;
	int process_count = -1;

	MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
	MPI_Comm_size(MPI_COMM_WORLD, &process_count);
	
	char hostname[MPI_MAX_PROCESSOR_NAME];
	int hostname_length = -1;
	MPI_Get_processor_name(hostname, &hostname_length);

	char message[MESSAGE_CAPACITY];
	if ( my_rank != 0 )
	{
		sprintf(message, "Hello from main thread of process %d of %d on %s", my_rank, process_count, hostname);
		MPI_Send(message, strlen(message) + 1, MPI_CHAR, /*dest*/ 0, /*tag*/ 0, MPI_COMM_WORLD);
	}
	else
	{
		for ( int source = 1; source < process_count; ++source )
		{
			MPI_Recv(message, MESSAGE_CAPACITY, MPI_CHAR, source, /*tag*/ 0, MPI_COMM_WORLD, /*MPI_Status *status*/ MPI_STATUS_IGNORE);
			printf("[%d] %s\n", source, message);
		}
	}

	MPI_Finalize();
	return 0;
}