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multiple.cpp
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Mon, Nov 4, 21:06

multiple.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
www.cs.sandia.gov/~sjplimp/lammps.html
Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
// example of how a calling program can invoke
// multiple instances of LAMMPS, each on a subset of procs,
// and have each of them perform a different run, and collect output info
// Syntax: mpirun -np P multiple N in.lammps T Tdelta
// P = # of total procs to run the driver program on
// N = # of instances of LAMMPS to create, P must be divisible by N
// in.lammps = LAMMPS input script,
// which takes "t" as a temperature variable
// T = baseline temperature
// Tdelta = incremental temperature for each of N runs
// See README for compilation instructions
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "mpi.h"
#include "lammps.h" // these are LAMMPS include files
#include "input.h"
#include "atom.h"
#include "library.h"
using namespace LAMMPS_NS;
int main(int narg, char **arg)
{
// setup MPI and various communicators
// driver runs on all procs in MPI_COMM_WORLD
// comm_lammps only has 1st P procs (could be all or any subset)
MPI_Init(&narg,&arg);
if (narg != 5) {
printf("Syntax: multiple N in.lammps T Tdelta\n");
exit(1);
}
int me,nprocs;
MPI_Comm_rank(MPI_COMM_WORLD,&me);
MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
int ninstance = atoi(arg[1]);
if (nprocs % ninstance) {
if (me == 0)
printf("ERROR: Total procs must be divisble by N\n");
MPI_Abort(MPI_COMM_WORLD,1);
}
char *infile = arg[2];
double temperature = atof(arg[3]);
double tdelta = atof(arg[4]);
// create one communicator per instancem each with P/N procs
int instance = me*ninstance / nprocs;
MPI_Comm comm_lammps;
MPI_Comm_split(MPI_COMM_WORLD,instance,0,&comm_lammps);
// each instance: unique screen file, log file, temperature
char str1[32],str2[32],str3[32];
char **lmparg = new char*[8];
lmparg[0] = NULL; // required placeholder for program name
lmparg[1] = (char *) "-screen";
sprintf(str1,"screen.%d",instance);
lmparg[2] = str1;
lmparg[3] = (char *) "-log";
sprintf(str2,"log.lammps.%d",instance);
lmparg[4] = str2;
lmparg[5] = (char *) "-var";
lmparg[6] = (char *) "t";
sprintf(str3,"%g",temperature + instance*tdelta);
lmparg[7] = str3;
// open N instances of LAMMPS
// either of these methods will work
LAMMPS *lmp = new LAMMPS(8,lmparg,comm_lammps);
//LAMMPS *lmp;
//lammps_open(8,lmparg,comm_lammps,(void **) &lmp);
delete [] lmparg;
// run input script thru all instances of LAMMPS
lammps_file(lmp,infile);
// query final temperature and print result for each instance
double *ptr = (double *)
lammps_extract_compute(lmp,(char *) "thermo_temp",0,0);
double finaltemp = *ptr;
double *temps = new double[ninstance];
for (int i = 0; i < ninstance; i++) temps[i] = 0.0;
int me_lammps;
MPI_Comm_rank(comm_lammps,&me_lammps);
if (me_lammps == 0) temps[instance] = finaltemp;
double *alltemps = new double[ninstance];
MPI_Allreduce(temps,alltemps,ninstance,MPI_DOUBLE,MPI_SUM,MPI_COMM_WORLD);
if (me == 0)
for (int i = 0; i < ninstance; i++)
printf("Instance %d, final temp = %g\n",i+1,alltemps[i]);
delete [] temps;
delete [] alltemps;
// delete LAMMPS instances
delete lmp;
// close down MPI
MPI_Comm_free(&comm_lammps);
MPI_Finalize();
}

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