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dihedral_fourier.cpp
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Mon, Jun 10, 11:37

dihedral_fourier.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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Loukas D. Peristeras (Scienomics SARL)
[ based on dihedral_charmm.cpp Paul Crozier (SNL) ]
------------------------------------------------------------------------- */
#include <mpi.h>
#include <math.h>
#include <stdlib.h>
#include "dihedral_fourier.h"
#include "atom.h"
#include "comm.h"
#include "neighbor.h"
#include "domain.h"
#include "force.h"
#include "pair.h"
#include "update.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
using namespace MathConst;
#define TOLERANCE 0.05
/* ---------------------------------------------------------------------- */
DihedralFourier::DihedralFourier(LAMMPS *lmp) : Dihedral(lmp)
{
writedata = 1;
}
/* ---------------------------------------------------------------------- */
DihedralFourier::~DihedralFourier()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(nterms);
for (int i=1; i<= atom->ndihedraltypes; i++) {
if ( k[i] ) delete [] k[i];
if ( multiplicity[i] ) delete [] multiplicity[i];
if ( shift[i] ) delete [] shift[i];
if ( cos_shift[i] ) delete [] cos_shift[i];
if ( sin_shift[i] ) delete [] sin_shift[i];
}
delete [] k;
delete [] multiplicity;
delete [] shift;
delete [] cos_shift;
delete [] sin_shift;
}
}
/* ---------------------------------------------------------------------- */
void DihedralFourier::compute(int eflag, int vflag)
{
int i1,i2,i3,i4,i,j,m,n,type;
double vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,vb2xm,vb2ym,vb2zm;
double edihedral,f1[3],f2[3],f3[3],f4[3];
double ax,ay,az,bx,by,bz,rasq,rbsq,rgsq,rg,rginv,ra2inv,rb2inv,rabinv;
double df,df1_,ddf1_,fg,hg,fga,hgb,gaa,gbb;
double dtfx,dtfy,dtfz,dtgx,dtgy,dtgz,dthx,dthy,dthz;
double c,s,p_,sx2,sy2,sz2;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = 0;
double **x = atom->x;
double **f = atom->f;
int **dihedrallist = neighbor->dihedrallist;
int ndihedrallist = neighbor->ndihedrallist;
int nlocal = atom->nlocal;
int newton_bond = force->newton_bond;
for (n = 0; n < ndihedrallist; n++) {
i1 = dihedrallist[n][0];
i2 = dihedrallist[n][1];
i3 = dihedrallist[n][2];
i4 = dihedrallist[n][3];
type = dihedrallist[n][4];
// 1st bond
vb1x = x[i1][0] - x[i2][0];
vb1y = x[i1][1] - x[i2][1];
vb1z = x[i1][2] - x[i2][2];
// 2nd bond
vb2x = x[i3][0] - x[i2][0];
vb2y = x[i3][1] - x[i2][1];
vb2z = x[i3][2] - x[i2][2];
vb2xm = -vb2x;
vb2ym = -vb2y;
vb2zm = -vb2z;
// 3rd bond
vb3x = x[i4][0] - x[i3][0];
vb3y = x[i4][1] - x[i3][1];
vb3z = x[i4][2] - x[i3][2];
ax = vb1y*vb2zm - vb1z*vb2ym;
ay = vb1z*vb2xm - vb1x*vb2zm;
az = vb1x*vb2ym - vb1y*vb2xm;
bx = vb3y*vb2zm - vb3z*vb2ym;
by = vb3z*vb2xm - vb3x*vb2zm;
bz = vb3x*vb2ym - vb3y*vb2xm;
rasq = ax*ax + ay*ay + az*az;
rbsq = bx*bx + by*by + bz*bz;
rgsq = vb2xm*vb2xm + vb2ym*vb2ym + vb2zm*vb2zm;
rg = sqrt(rgsq);
rginv = ra2inv = rb2inv = 0.0;
if (rg > 0) rginv = 1.0/rg;
if (rasq > 0) ra2inv = 1.0/rasq;
if (rbsq > 0) rb2inv = 1.0/rbsq;
rabinv = sqrt(ra2inv*rb2inv);
c = (ax*bx + ay*by + az*bz)*rabinv;
s = rg*rabinv*(ax*vb3x + ay*vb3y + az*vb3z);
// error check
if (c > 1.0 + TOLERANCE || c < (-1.0 - TOLERANCE)) {
int me;
MPI_Comm_rank(world,&me);
if (screen) {
char str[128];
sprintf(str,"Dihedral problem: %d " BIGINT_FORMAT " "
TAGINT_FORMAT " " TAGINT_FORMAT " "
TAGINT_FORMAT " " TAGINT_FORMAT,
me,update->ntimestep,
atom->tag[i1],atom->tag[i2],atom->tag[i3],atom->tag[i4]);
error->warning(FLERR,str,0);
fprintf(screen," 1st atom: %d %g %g %g\n",
me,x[i1][0],x[i1][1],x[i1][2]);
fprintf(screen," 2nd atom: %d %g %g %g\n",
me,x[i2][0],x[i2][1],x[i2][2]);
fprintf(screen," 3rd atom: %d %g %g %g\n",
me,x[i3][0],x[i3][1],x[i3][2]);
fprintf(screen," 4th atom: %d %g %g %g\n",
me,x[i4][0],x[i4][1],x[i4][2]);
}
}
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
// force and energy
// p = sum(i=1,nterms) k_i*(1+cos(n_i*phi-d_i)
// dp = dp / dphi
edihedral = 0.0;
df = 0.0;
for (j=0; j<nterms[type]; j++)
{
m = multiplicity[type][j];
p_ = 1.0;
ddf1_ = df1_ = 0.0;
for (i = 0; i < m; i++) {
ddf1_ = p_*c - df1_*s;
df1_ = p_*s + df1_*c;
p_ = ddf1_;
}
p_ = p_*cos_shift[type][j] + df1_*sin_shift[type][j];
df1_ = df1_*cos_shift[type][j] - ddf1_*sin_shift[type][j];
df1_ *= -m;
p_ += 1.0;
if (m == 0) {
p_ = 1.0 + cos_shift[type][j];
df1_ = 0.0;
}
if (eflag) edihedral += k[type][j] * p_;
df += (-k[type][j] * df1_);
}
fg = vb1x*vb2xm + vb1y*vb2ym + vb1z*vb2zm;
hg = vb3x*vb2xm + vb3y*vb2ym + vb3z*vb2zm;
fga = fg*ra2inv*rginv;
hgb = hg*rb2inv*rginv;
gaa = -ra2inv*rg;
gbb = rb2inv*rg;
dtfx = gaa*ax;
dtfy = gaa*ay;
dtfz = gaa*az;
dtgx = fga*ax - hgb*bx;
dtgy = fga*ay - hgb*by;
dtgz = fga*az - hgb*bz;
dthx = gbb*bx;
dthy = gbb*by;
dthz = gbb*bz;
sx2 = df*dtgx;
sy2 = df*dtgy;
sz2 = df*dtgz;
f1[0] = df*dtfx;
f1[1] = df*dtfy;
f1[2] = df*dtfz;
f2[0] = sx2 - f1[0];
f2[1] = sy2 - f1[1];
f2[2] = sz2 - f1[2];
f4[0] = df*dthx;
f4[1] = df*dthy;
f4[2] = df*dthz;
f3[0] = -sx2 - f4[0];
f3[1] = -sy2 - f4[1];
f3[2] = -sz2 - f4[2];
// apply force to each of 4 atoms
if (newton_bond || i1 < nlocal) {
f[i1][0] += f1[0];
f[i1][1] += f1[1];
f[i1][2] += f1[2];
}
if (newton_bond || i2 < nlocal) {
f[i2][0] += f2[0];
f[i2][1] += f2[1];
f[i2][2] += f2[2];
}
if (newton_bond || i3 < nlocal) {
f[i3][0] += f3[0];
f[i3][1] += f3[1];
f[i3][2] += f3[2];
}
if (newton_bond || i4 < nlocal) {
f[i4][0] += f4[0];
f[i4][1] += f4[1];
f[i4][2] += f4[2];
}
if (evflag)
ev_tally(i1,i2,i3,i4,nlocal,newton_bond,edihedral,f1,f3,f4,
vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z);
}
}
/* ---------------------------------------------------------------------- */
void DihedralFourier::allocate()
{
allocated = 1;
int n = atom->ndihedraltypes;
memory->create(nterms,n+1,"dihedral:nterms");
k = new double * [n+1];
multiplicity = new int * [n+1];
shift = new double * [n+1];
cos_shift = new double * [n+1];
sin_shift = new double * [n+1];
for (int i = 1; i <= n; i++) {
k[i] = shift[i] = cos_shift[i] = sin_shift[i] = 0;
multiplicity[i] = 0;
}
memory->create(setflag,n+1,"dihedral:setflag");
for (int i = 1; i <= n; i++) setflag[i] = 0;
}
/* ----------------------------------------------------------------------
set coeffs for one type
------------------------------------------------------------------------- */
void DihedralFourier::coeff(int narg, char **arg)
{
if (narg < 4) error->all(FLERR,"Incorrect args for dihedral coefficients");
if (!allocated) allocate();
int ilo,ihi;
force->bounds(FLERR,arg[0],atom->ndihedraltypes,ilo,ihi);
// require integer values of shift for backwards compatibility
// arbitrary phase angle shift could be allowed, but would break
// backwards compatibility and is probably not needed
double k_one;
int multiplicity_one;
double shift_one;
int nterms_one = force->inumeric(FLERR,arg[1]);
if (nterms_one < 1)
error->all(FLERR,"Incorrect number of terms arg for dihedral coefficients");
if (2+3*nterms_one < narg)
error->all(FLERR,"Incorrect number of arguments for dihedral coefficients");
int count = 0;
for (int i = ilo; i <= ihi; i++) {
nterms[i] = nterms_one;
k[i] = new double [nterms_one];
multiplicity[i] = new int [nterms_one];
shift[i] = new double [nterms_one];
cos_shift[i] = new double [nterms_one];
sin_shift[i] = new double [nterms_one];
for (int j = 0; j<nterms_one; j++) {
int offset = 1+3*j;
k_one = force->numeric(FLERR,arg[offset+1]);
multiplicity_one = force->inumeric(FLERR,arg[offset+2]);
shift_one = force->numeric(FLERR,arg[offset+3]);
k[i][j] = k_one;
multiplicity[i][j] = multiplicity_one;
shift[i][j] = shift_one;
cos_shift[i][j] = cos(MY_PI*shift_one/180.0);
sin_shift[i][j] = sin(MY_PI*shift_one/180.0);
}
setflag[i] = 1;
count++;
}
if (count == 0) error->all(FLERR,"Incorrect args for dihedral coefficients");
}
/* ----------------------------------------------------------------------
proc 0 writes out coeffs to restart file
------------------------------------------------------------------------- */
void DihedralFourier::write_restart(FILE *fp)
{
fwrite(&nterms[1],sizeof(int),atom->ndihedraltypes,fp);
for(int i = 1; i <= atom->ndihedraltypes; i++) {
fwrite(k[i],sizeof(double),nterms[i],fp);
fwrite(multiplicity[i],sizeof(int),nterms[i],fp);
fwrite(shift[i],sizeof(double),nterms[i],fp);
}
}
/* ----------------------------------------------------------------------
proc 0 reads coeffs from restart file, bcasts them
------------------------------------------------------------------------- */
void DihedralFourier::read_restart(FILE *fp)
{
allocate();
if (comm->me == 0)
fread(&nterms[1],sizeof(int),atom->ndihedraltypes,fp);
MPI_Bcast(&nterms[1],atom->ndihedraltypes,MPI_INT,0,world);
// allocate
for (int i=1; i<=atom->ndihedraltypes; i++) {
k[i] = new double [nterms[i]];
multiplicity[i] = new int [nterms[i]];
shift[i] = new double [nterms[i]];
cos_shift[i] = new double [nterms[i]];
sin_shift[i] = new double [nterms[i]];
}
if (comm->me == 0) {
for (int i=1; i<=atom->ndihedraltypes; i++) {
fread(k[i],sizeof(double),nterms[i],fp);
fread(multiplicity[i],sizeof(int),nterms[i],fp);
fread(shift[i],sizeof(double),nterms[i],fp);
}
}
for (int i=1; i<=atom->ndihedraltypes; i++) {
MPI_Bcast(k[i],nterms[i],MPI_DOUBLE,0,world);
MPI_Bcast(multiplicity[i],nterms[i],MPI_INT,0,world);
MPI_Bcast(shift[i],nterms[i],MPI_DOUBLE,0,world);
}
for (int i=1; i <= atom->ndihedraltypes; i++) {
setflag[i] = 1;
for (int j = 0; j < nterms[i]; j++) {
cos_shift[i][j] = cos(MY_PI*shift[i][j]/180.0);
sin_shift[i][j] = sin(MY_PI*shift[i][j]/180.0);
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to data file
------------------------------------------------------------------------- */
void DihedralFourier::write_data(FILE *fp)
{
for (int i = 1; i <= atom->ndihedraltypes; i++)
{
fprintf(fp,"%d %d",i,nterms[i]);
for(int j = 0; j < nterms[i]; j++)
fprintf(fp," %g %d %g",k[i][j],multiplicity[i][j],shift[i][j]);
fprintf(fp,"\n");
}
}

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