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fix_gravity.cpp
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Wed, Sep 4, 04:04

fix_gravity.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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "fix_gravity.h"
#include "atom.h"
#include "update.h"
#include "domain.h"
#include "respa.h"
#include "modify.h"
#include "input.h"
#include "variable.h"
#include "math_const.h"
#include "error.h"
#include "force.h"
using namespace LAMMPS_NS;
using namespace FixConst;
using namespace MathConst;
enum{CHUTE,SPHERICAL,VECTOR};
enum{CONSTANT,EQUAL};
/* ---------------------------------------------------------------------- */
FixGravity::FixGravity(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg),
mstr(NULL), vstr(NULL), pstr(NULL), tstr(NULL), xstr(NULL), ystr(NULL), zstr(NULL)
{
if (narg < 5) error->all(FLERR,"Illegal fix gravity command");
dynamic_group_allow = 1;
scalar_flag = 1;
global_freq = 1;
extscalar = 1;
respa_level_support = 1;
ilevel_respa = 0;
mstr = vstr = pstr = tstr = xstr = ystr = zstr = NULL;
mstyle = vstyle = pstyle = tstyle = xstyle = ystyle = zstyle = CONSTANT;
if (strstr(arg[3],"v_") == arg[3]) {
int n = strlen(&arg[3][2]) + 1;
mstr = new char[n];
strcpy(mstr,&arg[3][2]);
mstyle = EQUAL;
} else {
magnitude = force->numeric(FLERR,arg[3]);
mstyle = CONSTANT;
}
if (strcmp(arg[4],"chute") == 0) {
if (narg != 6) error->all(FLERR,"Illegal fix gravity command");
style = CHUTE;
if (strstr(arg[5],"v_") == arg[5]) {
int n = strlen(&arg[5][2]) + 1;
vstr = new char[n];
strcpy(vstr,&arg[5][2]);
vstyle = EQUAL;
} else {
vert = force->numeric(FLERR,arg[5]);
vstyle = CONSTANT;
}
} else if (strcmp(arg[4],"spherical") == 0) {
if (narg != 7) error->all(FLERR,"Illegal fix gravity command");
style = SPHERICAL;
if (strstr(arg[5],"v_") == arg[5]) {
int n = strlen(&arg[5][2]) + 1;
pstr = new char[n];
strcpy(pstr,&arg[5][2]);
pstyle = EQUAL;
} else {
phi = force->numeric(FLERR,arg[5]);
pstyle = CONSTANT;
}
if (strstr(arg[6],"v_") == arg[6]) {
int n = strlen(&arg[6][2]) + 1;
tstr = new char[n];
strcpy(tstr,&arg[6][2]);
tstyle = EQUAL;
} else {
theta = force->numeric(FLERR,arg[6]);
tstyle = CONSTANT;
}
} else if (strcmp(arg[4],"vector") == 0) {
if (narg != 8) error->all(FLERR,"Illegal fix gravity command");
style = VECTOR;
if (strstr(arg[5],"v_") == arg[5]) {
int n = strlen(&arg[5][2]) + 1;
xstr = new char[n];
strcpy(xstr,&arg[5][2]);
xstyle = EQUAL;
} else {
xdir = force->numeric(FLERR,arg[5]);
xstyle = CONSTANT;
}
if (strstr(arg[6],"v_") == arg[6]) {
int n = strlen(&arg[6][2]) + 1;
ystr = new char[n];
strcpy(ystr,&arg[6][2]);
ystyle = EQUAL;
} else {
ydir = force->numeric(FLERR,arg[6]);
ystyle = CONSTANT;
}
if (strstr(arg[7],"v_") == arg[7]) {
int n = strlen(&arg[7][2]) + 1;
zstr = new char[n];
strcpy(zstr,&arg[7][2]);
zstyle = EQUAL;
} else {
zdir = force->numeric(FLERR,arg[7]);
zstyle = CONSTANT;
}
} else error->all(FLERR,"Illegal fix gravity command");
degree2rad = MY_PI/180.0;
time_origin = update->ntimestep;
eflag = 0;
egrav = 0.0;
}
/* ---------------------------------------------------------------------- */
FixGravity::~FixGravity()
{
delete [] mstr;
delete [] vstr;
delete [] pstr;
delete [] tstr;
delete [] xstr;
delete [] ystr;
delete [] zstr;
}
/* ---------------------------------------------------------------------- */
int FixGravity::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= THERMO_ENERGY;
mask |= POST_FORCE_RESPA;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixGravity::init()
{
if (strstr(update->integrate_style,"respa")) {
ilevel_respa = ((Respa *) update->integrate)->nlevels-1;
if (respa_level >= 0) ilevel_respa = MIN(respa_level,ilevel_respa);
}
// check variables
if (mstr) {
mvar = input->variable->find(mstr);
if (mvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(mvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (vstr) {
vvar = input->variable->find(vstr);
if (vvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(vvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (pstr) {
pvar = input->variable->find(pstr);
if (pvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(pvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (tstr) {
tvar = input->variable->find(tstr);
if (tvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(tvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (xstr) {
xvar = input->variable->find(xstr);
if (xvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(xvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (ystr) {
yvar = input->variable->find(ystr);
if (yvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(yvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
if (zstr) {
zvar = input->variable->find(zstr);
if (zvar < 0)
error->all(FLERR,"Variable name for fix gravity does not exist");
if (!input->variable->equalstyle(zvar))
error->all(FLERR,"Variable for fix gravity is invalid style");
}
varflag = CONSTANT;
if (mstyle != CONSTANT || vstyle != CONSTANT || pstyle != CONSTANT ||
tstyle != CONSTANT || xstyle != CONSTANT || ystyle != CONSTANT ||
zstyle != CONSTANT) varflag = EQUAL;
// set gravity components once and for all
if (varflag == CONSTANT) set_acceleration();
}
/* ---------------------------------------------------------------------- */
void FixGravity::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 FixGravity::post_force(int vflag)
{
// update gravity due to variables
if (varflag != CONSTANT) {
modify->clearstep_compute();
if (mstyle == EQUAL) magnitude = input->variable->compute_equal(mvar);
if (vstyle == EQUAL) vert = input->variable->compute_equal(vvar);
if (pstyle == EQUAL) phi = input->variable->compute_equal(pvar);
if (tstyle == EQUAL) theta = input->variable->compute_equal(tvar);
if (xstyle == EQUAL) xdir = input->variable->compute_equal(xvar);
if (ystyle == EQUAL) ydir = input->variable->compute_equal(yvar);
if (zstyle == EQUAL) zdir = input->variable->compute_equal(zvar);
modify->addstep_compute(update->ntimestep + 1);
set_acceleration();
}
double **x = atom->x;
double **f = atom->f;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *mask = atom->mask;
int *type = atom->type;
int nlocal = atom->nlocal;
double massone;
eflag = 0;
egrav = 0.0;
if (rmass) {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
massone = rmass[i];
f[i][0] += massone*xacc;
f[i][1] += massone*yacc;
f[i][2] += massone*zacc;
egrav -= massone * (xacc*x[i][0] + yacc*x[i][1] + zacc*x[i][2]);
}
} else {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
massone = mass[type[i]];
f[i][0] += massone*xacc;
f[i][1] += massone*yacc;
f[i][2] += massone*zacc;
egrav -= massone * (xacc*x[i][0] + yacc*x[i][1] + zacc*x[i][2]);
}
}
}
/* ---------------------------------------------------------------------- */
void FixGravity::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == ilevel_respa) post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixGravity::set_acceleration()
{
if (style == CHUTE || style == SPHERICAL) {
if (style == CHUTE) {
phi = 0.0;
theta = 180.0 - vert;
}
if (domain->dimension == 3) {
xgrav = sin(degree2rad * theta) * cos(degree2rad * phi);
ygrav = sin(degree2rad * theta) * sin(degree2rad * phi);
zgrav = cos(degree2rad * theta);
} else {
xgrav = sin(degree2rad * theta);
ygrav = cos(degree2rad * theta);
zgrav = 0.0;
}
} else if (style == VECTOR) {
if (domain->dimension == 3) {
double length = sqrt(xdir*xdir + ydir*ydir + zdir*zdir);
xgrav = xdir/length;
ygrav = ydir/length;
zgrav = zdir/length;
} else {
double length = sqrt(xdir*xdir + ydir*ydir);
xgrav = xdir/length;
ygrav = ydir/length;
zgrav = 0.0;
}
}
xacc = magnitude*xgrav;
yacc = magnitude*ygrav;
zacc = magnitude*zgrav;
}
/* ----------------------------------------------------------------------
potential energy in gravity field
------------------------------------------------------------------------- */
double FixGravity::compute_scalar()
{
// only sum across procs one time
if (eflag == 0) {
MPI_Allreduce(&egrav,&egrav_all,1,MPI_DOUBLE,MPI_SUM,world);
eflag = 1;
}
return egrav_all;
}

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