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min_cg_fr.cpp
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Wed, Jul 17, 13:47

min_cg_fr.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
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.
------------------------------------------------------------------------- */
#include "math.h"
#include "mpi.h"
#include "min_cg_fr.h"
#include "atom.h"
#include "update.h"
#include "output.h"
#include "timer.h"
using namespace LAMMPS_NS;
#define MIN(A,B) ((A) < (B)) ? (A) : (B)
#define MAX(A,B) ((A) > (B)) ? (A) : (B)
#define EPS 1.0e-6
/* ---------------------------------------------------------------------- */
MinCGFR::MinCGFR(LAMMPS *lmp) : MinCG(lmp) {}
/* ----------------------------------------------------------------------
minimization via conjugate gradient iterations
Fletcher-Reeves formulation
------------------------------------------------------------------------- */
void MinCGFR::iterate(int n)
{
int i,gradsearch,fail;
double alpha,beta,gg,dot,dotall;
double *f;
f = atom->f[0];
for (int i = 0; i < ndof; i++) h[i] = g[i] = f[i];
dot = 0.0;
for (i = 0; i < ndof; i++) dot += f[i]*f[i];
MPI_Allreduce(&dot,&gg,1,MPI_DOUBLE,MPI_SUM,world);
neval = 0;
gradsearch = 1;
for (niter = 0; niter < n; niter++) {
update->ntimestep++;
// line minimization along direction h from current atom->x
eprevious = ecurrent;
fail = (this->*linemin)(ndof,atom->x[0],h,ecurrent,dmin,dmax,alpha,neval);
// if max_eval exceeded, all done
// if linemin failed or energy did not decrease sufficiently:
// all done if searched in grad direction
// else force next search to be in grad direction (CG restart)
if (neval >= update->max_eval) break;
if (fail || fabs(ecurrent-eprevious) <=
update->tolerance * 0.5*(fabs(ecurrent) + fabs(eprevious) + EPS)) {
if (gradsearch == 1) break;
gradsearch = -1;
}
// update h from new f = -Grad(x) and old g
// old g,h must have migrated with atoms to do this correctly
// done if size sq of grad vector < EPS
// force new search dir to be grad dir if need to restart CG
// set gradsesarch to 1 if will search in grad dir on next iteration
f = atom->f[0];
dot = 0.0;
for (i = 0; i < ndof; i++) dot += f[i]*f[i];
MPI_Allreduce(&dot,&dotall,1,MPI_DOUBLE,MPI_SUM,world);
beta = dotall/gg;
gg = dotall;
if (gg < EPS) break;
if (gradsearch == -1) beta = 0.0;
if (beta == 0.0) gradsearch = 1;
else gradsearch = 0;
for (i = 0; i < ndof; i++) {
g[i] = f[i];
h[i] = g[i] + beta*h[i];
}
// output for thermo, dump, restart files
if (output->next == update->ntimestep) {
timer->stamp();
output->write(update->ntimestep);
timer->stamp(TIME_OUTPUT);
}
}
}

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