compile with: mpicc mpi_example1.c -o mpi_example1

run with: mpirun -n 4 mpi_example1

   or: mpirun -np 4 --host h1,h2,h3,h4 mpi_example1

   or: mpirun -np 4 --hostfile mpi_hosts mpi_example1

   or: mpirun -np 4 --hostfile mpi_hosts --map-by node mpi_example1

---

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

int main( int argc, char **argv )
{
	int rank, size;
	char processor_name[MPI_MAX_PROCESSOR_NAME];
	int namelen;

	MPI_Init( &argc, &argv );
	
	MPI_Comm_rank( MPI_COMM_WORLD, &rank );
	MPI_Comm_size( MPI_COMM_WORLD, &size );
	MPI_Get_processor_name(processor_name,&namelen);
	printf( "Jestem %d z %d na %s\n", rank, size, processor_name );

	MPI_Finalize();
}

---

#include <mpi.h>
#include <stdio.h>
#define MSG_HELLO 100
#define MSG_SIZE 2

int main( int argc, char **argv )
{
	int rank,size,sender=0,receiver=1;
	int msg[MSG_SIZE];
	MPI_Status status;

	MPI_Init(&argc, &argv);

	MPI_Comm_rank( MPI_COMM_WORLD, &rank );

	if ( rank == sender )
	{
		msg[0] = rank;
		MPI_Comm_size( MPI_COMM_WORLD, &size );
		msg[1] = size;
		printf("%d: Wysylam (%d %d) do %d\n", rank, msg[0], msg[1], receiver);
		MPI_Send( msg, MSG_SIZE, MPI_INT, receiver, MSG_HELLO, MPI_COMM_WORLD );
	}
	else if ( rank == receiver )
	{
		MPI_Recv(msg, MSG_SIZE, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
		MPI_Get_count( &status, MPI_INT, &size);
		printf("%d: Otrzymalem %d wartosci: (%d %d) od %d\n", rank, size, msg[0], msg[1], status.MPI_SOURCE);
	}
	MPI_Finalize();
}

---

#include <mpi.h>
#include <stdio.h>
#define MSG_SIZE 2

int main(int argc, char **argv)
{
	int rank,size,sender;
	MPI_Status status;

	MPI_Init(&argc, &argv);

	MPI_Comm_rank( MPI_COMM_WORLD, &rank );

	int msg[MSG_SIZE];

	sender = 0;

	if ( rank == sender )
	{
		msg[0] = rank;
		MPI_Comm_size( MPI_COMM_WORLD, &size );
		msg[1] = size;
		MPI_Bcast(msg, MSG_SIZE, MPI_INT, sender, MPI_COMM_WORLD);
	}
	else
	{
		MPI_Bcast( msg, MSG_SIZE, MPI_INT, sender, MPI_COMM_WORLD );
		printf("%d: Otrzymalem bcast (%d %d) od %d\n", rank, msg[0], msg[1], sender);
	}
	MPI_Finalize();
}

---

#include <mpi.h>
#include <stdio.h>
#define MSG_SIZE 1

int main(int argc, char **argv)
{
	int rank,receiver;
	MPI_Status status;

	MPI_Init(&argc, &argv);

	MPI_Comm_rank( MPI_COMM_WORLD, &rank );

	int i=rank;
	int sum=0;
	receiver = 0;

	printf("%d: Wysylam wartosc %d \n", rank, i );

	MPI_Reduce(&i,&sum, MSG_SIZE, MPI_INT, MPI_SUM, receiver, MPI_COMM_WORLD);

	if ( rank == receiver ) printf("%d: Otrzymalem sume %d \n", rank, sum );
		
	MPI_Finalize();
}