Dist. y Paralelos: Message Passing Interface (MPI) [Contribution]

Message Passing Interface (MPI) is a standardized and portable message-passing system designed by a group of researchers from academia and industry to function on a wide variety of parallel computers. The standard defines the syntax and semantics of a core of library routines useful to a wide range of users writing portable message-passing programs in Fortran 77 or the C programming language. Several well-tested and efficient implementations of MPI include some that are free and in the public domain. These fostered the development of a parallel software industry, and there encouraged development of portable and scalable large-scale parallel applications.

To start your first code with MPI, you must include the library

#include <mpi.h> /*para C/C++*/

Install MPI

// sudo aptitude install mpich-bin libmpich1.0-dev ssh

// sudo /etc/init.d/ssh start

Configure SSH

$ ssh-keygen -t dsa
$ cd ~/.ssh
$ cat id_dsa.pub >> authorized_keys

Going to do a hello world as an example:

Hello World C

/* C Example */
#include <stdio.h>
#include <mpi.h>

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

  MPI_Init (&argc, &argv);   /* starts MPI */
  MPI_Comm_rank (MPI_COMM_WORLD, &rank);        /* get current process id */
  MPI_Comm_size (MPI_COMM_WORLD, &size);        /* get number of processes */
  printf( "Hello world from process %d of %d\n", rank, size );
  MPI_Finalize();
  return 0;
}

 //  mpicc hello.c -o hellompi

//  mpiexec -n 5 hellompi

 Where the four numbers is the process

Hello world C ++

/* C++ Example */
#include <mpi.h>
#include <iostream>
#include <stdio.h>

using namespace std;

int main (int argc,char *argv[])
{int rank,size;
 MPI_Init(&argc,&argv);
 MPI_Comm_size(MPI_COMM_WORLD, &size);
 MPI_Comm_rank(MPI_COMM_WORLD, &rank);
 printf("Hola Mundo desde procesador %d\n",rank);
 MPI_Finalize();
 return 0;
}

mpic++ -o Hola HolaMundo.cpp
mpirun -np 4 Hola

have to generate something like this

user@user ~$ mpirun -np 4 ./hellompi 
Hello world from process 0 of 4
Hello world from process 2 of 4
Hello world from process 1 of 4
Hello world from process 3 of 4

http://www.open-mpi.org/
http://www.mancera.org/2010/12/08/montar-un-cluster-en-linux-ubuntu/
http://www.cs.ucsb.edu/~hnielsen/cs140/openmpi-install.html