Compiling and Running MPI/C Code on Odyssey

A simple MPI example C code is:

#include <stdio.h>

#include <mpi.h>



#define BUFSIZE 128



main(int argc, char *argv[])

{

        char name[BUFSIZ];

        int length;

        int n;



        MPI_Init(&argc, &argv);

        MPI_Comm_rank(MPI_COMM_WORLD, &n);

        if (n==0)

          {

            length=10.;

          }

        MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);

        MPI_Get_processor_name(name, &length);

        MPI_Barrier(MPI_COMM_WORLD); 

        printf("%s: hello world. n=%dn", name, n);

        MPI_Barrier(MPI_COMM_WORLD); 

        MPI_Finalize();

}

A Makefile to go with this would be:

CC=mpicc

CFLAGS=-O -g

LIBS=-lm

RM=/bin/rm



EXECS = hello

OBJS = hello.o 



all: $(EXECS)



$(EXECS): $(OBJS) Makefile

        $(CC) $(CFLAGS) -o $(EXECS) $(OBJS) $(LIBS)



$(OBJS): Makefile



.c.o:

        $(CC) $(CFLAGS) -o $*.o -c $*.c

clean:

        $(RM) -f $(EXECS) $(OBJS) gmon.out *~ *.o *.oo

A LSF submission script to submit this job could be:

#!/bin/sh

#BSUB -u rchelp@fas.harvard.edu

#BSUB -J hello_world

#BSUB -o hello_lsf.out

#BSUB -e hello_lsf.err

#BSUB -n 16

#BSUB -q short_parallel

#BSUB -a openmpi



mpirun.lsf ./hello 1> hello.out 2> hello.err

To debug your MPI code you should use Totalview. Look at our FAQ on debugging parallel code for more information.


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