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Lightning user doc contents
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SPMD parallel job example using MPI-standard message passing
This example uses MPI SPMD (Message Passing Interface-standard
Single Processor Multiple Data structures) to sum a set of 1,000,000
exponentials. The Message Passing Interface is a standardized
programming paradigm for parallel computers designed to allow
separate processes to efficiently communicate with each other
via messages.
Note that this example starts two identical processes (process 1
and process 0) that have different execution paths (tasks). The
execution path in process 1 performs the calculation and sends that
sum to process 0. Process 0 waits until it receives the sum from
process 1, then prints the sum. The code for both processes is
identical, and the execution path is determined by testing the value
of the process id. This is noted by the comments in the code.
This example consists of four parts:
- A script for the LSF batch subsystem that submits the job
to lightning
- Fortran code that runs the example
- C code that runs the same example
- C++ code that runs the same example
To run this example, you have two choices:
In the /usr/local/examples/lsf/batch/ directory on lightning:
cp mpi.* $PWD
Submit the example codes to the LSF batch subsystem by entering:
bsub < mpi.lsf Copy the codes on this page and paste them into your own
files:
- Copy the
LSF batch job script below and paste it into
a file named mpi.lsf
in your working directory on lightning.
- Copy the
Fortran code below and paste it into a file named
mpi.f in your working directory on lightning.
- Copy the
C code below and paste it into a file named
mpi.c in your working directory on lightning.
- Copy the
C++ code below and paste it into a file named
mpi.cc in your working directory on lightning.
- Submit the example codes to the LSF batch subsystem by
entering:
bsub < mpi.lsf
Studying this example will help you prepare your own SPMD jobs
for submittal to lightning via LSF.
#!/bin/ksh
#
# LSF batch script to run an SPMD/MPI code
#
#BSUB -a mpich_gm # select the mpich-gm elim
#BSUB -x # exlusive use of node (not_shared)
#BSUB -n 2 # number of total tasks
#BSUB -R "span[ptile=1]" # run 1 task per node
#BSUB -o mpilsf.out # output filename (%J to add job id)
#BSUB -e mpilsf.err # error filename
#BSUB -J mpilsf.test # job name
#BSUB -q regular # queue
# Run this executable in SPMD mode:
# Fortran example
mpif90 -Mextend -o mpif mpi.f
mpirun.lsf ./mpif
rm mpif
# C example
mpicc -o mpic mpi.c
mpirun.lsf ./mpic
rm mpic
# C++ example
mpicxx --no_auto_instantiation -o mpicc mpi.cc
mpirun.lsf ./mpicc
rm .mpicc
program main
implicit none
include 'mpif.h'
character (len=MPI_MAX_PROCESSOR_NAME) nodename
integer name_len, ierr
! Establish the number of the process being run with the variable "rank"
integer i
integer rank,error,tag,length,status(MPI_STATUS_SIZE)
integer hz, clock0, clock1, t
real(kind=8):: sum, buf(2), elapsed
call mpi_init(error)
! Assign the process number to the current process with "rank"
call mpi_comm_rank(MPI_COMM_WORLD,rank,error)
length=2
tag=999
! Test for the process being run, then calculate sum (process 1) or
! print sum (process 0)
call system_clock(count_rate = hz)
call system_clock(count = clock0)
if (rank .eq. 1) then
sum=0.0
do i=1,1000000
sum=sum+exp(.00000001*i)
end do
call system_clock(count = clock1)
elapsed = real(clock1 - clock0) / hz
buf(1)=sum
buf(2)=elapsed/1000.0
call mpi_send(buf,length,MPI_REAL8,0,tag,MPI_COMM_WORLD,error)
call MPI_GET_PROCESSOR_NAME(nodename, name_len, ierr)
print *,'f90 MPI task ', rank,' data sent from node ', nodename(1:name_len)
elseif (rank .eq. 0) then
call MPI_GET_PROCESSOR_NAME(nodename, name_len, ierr)
print *,'f90 MPI task ', rank,' data received on node ', nodename(1:name_len)
call mpi_recv(buf,length,MPI_REAL8,1,tag,MPI_COMM_WORLD,status,error)
print 10, buf(1), buf(2)
10 format(' f90 MPI Results: Sum = ',1pe12.6,' Loop time = ', 0pf12.8)
end if
call mpi_finalize(error)
stop
end
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <mpi.h>
/* Establish the number of the process being run with the variable "rank" */
main(int argc,char **argv)
{
MPI_Status status;
int i;
int rank,error,tag=42,length=2;
double buf[2], sum=0.0, elapsed, rtc();
int name_len;
char nodename[MPI_MAX_PROCESSOR_NAME];
error = MPI_Init(&argc,&argv);
/* Assign the process number to the current process with "rank" */
error=MPI_Comm_rank(MPI_COMM_WORLD,&rank);
/* Test for the process being run, then calculate sum (process 1) or */
/* print sum (process 0) */
if(rank==1)
{
elapsed=rtc();
for(i=1; i<1000000; i++)
{
sum += exp( .00000001 * (double)i );
}
elapsed=rtc()-elapsed;
buf[0]=sum;
buf[1]=elapsed;
error = MPI_Send(&buf, length, MPI_DOUBLE,0,tag,MPI_COMM_WORLD);
MPI_Get_processor_name(nodename, &name_len);
printf(" c MPI task %4d data sent from node %s\n", rank, nodename);
}
else
{
error=MPI_Recv(&buf,length,MPI_DOUBLE,1,tag,MPI_COMM_WORLD,&status);
MPI_Get_processor_name(nodename, &name_len);
printf(" c MPI task %4d data received on node %s\n", rank, nodename);
printf( " c MPI Results: Sum = %11e Loop time = %8f \n",buf[0],buf[1] );
}
error=MPI_Finalize();
exit (0);
}
double rtc()
{
static struct timeval time;
gettimeofday(&time,NULL);
return ( (double)(time.tv_sec)+(double)(time.tv_usec)/1000000.0 );
}
#include <iostream>
#include <string>
#include <math.h>
#include <mpi.h>
#include <sys/time.h>
using namespace std;
//---------------Class Defs-----------------------------------------------
class exp_sum {
public:
double elapsed;
double sum();
private:
double summer;
struct timeval time;
double rtc();
};
double exp_sum::sum()
{
int i;
summer=0.0;
elapsed=rtc();
for(i=1; i<1000000; i++)
{
summer += exp( .00000001 * (double)i );
}
elapsed=rtc()-elapsed;
return summer;
};
double exp_sum:: rtc()
{
gettimeofday(&time,NULL);
return ( (double)(time.tv_sec*1000000+time.tv_usec)/1000000 );
};
//----------------------------------------------------------------------- ---
//--------------Main Program--------------------------------------------------
int main(int argc,char **argv)
{
exp_sum total;
MPI_Status status;
int rank,error,tag=99,length=2;
double buf[2];
int name_len;
char nodename[MPI_MAX_PROCESSOR_NAME];
error = MPI_Init(&argc,&argv);
error=MPI_Comm_rank(MPI_COMM_WORLD,&rank);
if(rank==1)
{
buf[0]=total.sum();
buf[1]=total.elapsed;
error = MPI_Send(&buf, length, MPI_DOUBLE,0,tag,MPI_COMM_WORLD);
MPI_Get_processor_name(nodename, &name_len);
cout << " c++ MPI task " << rank << " data sent from node " << \
nodename << endl;
}
else
{
error=MPI_Recv(&buf,length,MPI_DOUBLE,1,tag,MPI_COMM_WORLD,&status);
MPI_Get_processor_name(nodename, &name_len);
cout << " c++ MPI task " << rank << " data received on node " << \
nodename << endl;
cout << " c++ mpi Results: Sum = " << buf[0] << " Loop time = " << buf[1] << '\n';
}
error=MPI_Finalize();
return 0;
}
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© Copyright 2005. University Corporation for Atmospheric
Research (UCAR). All Rights Reserved.
Address of this page:
http://www.scd.ucar.edu/docs/lightning/examples/spmd.jsp
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