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lammps/src/fix_spring_chunk.cpp
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fix_spring_chunk.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 <stdlib.h>
#include <string.h>
#include "fix_spring_chunk.h"
#include "atom.h"
#include "update.h"
#include "force.h"
#include "respa.h"
#include "domain.h"
#include "modify.h"
#include "compute_chunk_atom.h"
#include "compute_com_chunk.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
using namespace FixConst;
#define SMALL 1.0e-10
/* ---------------------------------------------------------------------- */
FixSpringChunk::FixSpringChunk(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg != 6) error->all(FLERR,"Illegal fix spring/chunk command");
scalar_flag = 1;
global_freq = 1;
extscalar = 1;
respa_level_support = 1;
ilevel_respa = 0;
k_spring = force->numeric(FLERR,arg[3]);
int n = strlen(arg[4]) + 1;
idchunk = new char[n];
strcpy(idchunk,arg[4]);
n = strlen(arg[5]) + 1;
idcom = new char[n];
strcpy(idcom,arg[5]);
esprings = 0.0;
com0 = fcom = NULL;
nchunk = 0;
}
/* ---------------------------------------------------------------------- */
FixSpringChunk::~FixSpringChunk()
{
memory->destroy(com0);
memory->destroy(fcom);
// decrement lock counter in compute chunk/atom, it if still exists
int icompute = modify->find_compute(idchunk);
if (icompute >= 0) {
cchunk = (ComputeChunkAtom *) modify->compute[icompute];
cchunk->unlock(this);
cchunk->lockcount--;
}
delete [] idchunk;
delete [] idcom;
}
/* ---------------------------------------------------------------------- */
int FixSpringChunk::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= THERMO_ENERGY;
mask |= POST_FORCE_RESPA;
mask |= MIN_POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::init()
{
// current indices for idchunk and idcom
int icompute = modify->find_compute(idchunk);
if (icompute < 0)
error->all(FLERR,"Chunk/atom compute does not exist for fix spring/chunk");
cchunk = (ComputeChunkAtom *) modify->compute[icompute];
if (strcmp(cchunk->style,"chunk/atom") != 0)
error->all(FLERR,"Fix spring/chunk does not use chunk/atom compute");
icompute = modify->find_compute(idcom);
if (icompute < 0)
error->all(FLERR,"Com/chunk compute does not exist for fix spring/chunk");
ccom = (ComputeCOMChunk *) modify->compute[icompute];
if (strcmp(ccom->style,"com/chunk") != 0)
error->all(FLERR,"Fix spring/chunk does not use com/chunk compute");
// check that idchunk is consistent with ccom->idchunk
if (strcmp(idchunk,ccom->idchunk) != 0)
error->all(FLERR,"Fix spring chunk chunkID not same as comID chunkID");
if (strstr(update->integrate_style,"respa")) {
ilevel_respa = ((Respa *) update->integrate)->nlevels-1;
if (respa_level >= 0) ilevel_respa = MIN(respa_level,ilevel_respa);
}
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::setup(int vflag)
{
if (strstr(update->integrate_style,"verlet"))
post_force(vflag);
else {
((Respa *) update->integrate)->copy_flevel_f(ilevel_respa);
post_force_respa(vflag,ilevel_respa,0);
((Respa *) update->integrate)->copy_f_flevel(ilevel_respa);
}
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::min_setup(int vflag)
{
post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::post_force(int vflag)
{
int i,m;
double dx,dy,dz,r;
// check if first time cchunk will be queried via ccom
// if so, lock idchunk for as long as this fix is in place
// will be unlocked in destructor
// necessary b/c this fix stores original COM
if (com0 == NULL) cchunk->lock(this,update->ntimestep,-1);
// calculate current centers of mass for each chunk
// extract pointers from idchunk and idcom
ccom->compute_array();
nchunk = cchunk->nchunk;
int *ichunk = cchunk->ichunk;
double *masstotal = ccom->masstotal;
double **com = ccom->array;
// check if first time cchunk was queried via ccom
// if so, allocate com0,fcom and store initial COM
if (com0 == NULL) {
memory->create(com0,nchunk,3,"spring/chunk:com0");
memory->create(fcom,nchunk,3,"spring/chunk:fcom");
for (m = 0; m < nchunk; m++) {
com0[m][0] = com[m][0];
com0[m][1] = com[m][1];
com0[m][2] = com[m][2];
}
}
// calculate fcom = force on each COM, divided by masstotal
esprings = 0.0;
for (m = 0; m < nchunk; m++) {
dx = com[m][0] - com0[m][0];
dy = com[m][1] - com0[m][1];
dz = com[m][2] - com0[m][2];
r = sqrt(dx*dx + dy*dy + dz*dz);
r = MAX(r,SMALL);
if (masstotal[m]) {
fcom[m][0] = k_spring*dx/r / masstotal[m];
fcom[m][1] = k_spring*dy/r / masstotal[m];
fcom[m][2] = k_spring*dz/r / masstotal[m];
esprings += 0.5*k_spring*r*r;
}
}
// apply restoring force to atoms in each chunk
double **f = atom->f;
int *type = atom->type;
double *mass = atom->mass;
double *rmass = atom->rmass;
int nlocal = atom->nlocal;
double massone;
if (rmass) {
for (i = 0; i < nlocal; i++) {
m = ichunk[i]-1;
if (m < 0) continue;
massone = rmass[i];
f[i][0] -= fcom[m][0]*massone;
f[i][1] -= fcom[m][1]*massone;
f[i][2] -= fcom[m][2]*massone;
}
} else {
for (i = 0; i < nlocal; i++) {
m = ichunk[i]-1;
if (m < 0) continue;
massone = mass[type[i]];
f[i][0] -= fcom[m][0]*massone;
f[i][1] -= fcom[m][1]*massone;
f[i][2] -= fcom[m][2]*massone;
}
}
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == ilevel_respa) post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixSpringChunk::min_post_force(int vflag)
{
post_force(vflag);
}
/* ----------------------------------------------------------------------
energy of stretched spring
------------------------------------------------------------------------- */
double FixSpringChunk::compute_scalar()
{
return esprings;
}
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