lammps/src/MISC/fix_srp.cpp

// clang-format off
/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, 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 authors: Timothy Sirk (ARL), Pieter in't Veld (BASF)
------------------------------------------------------------------------- */

#include "fix_srp.h"

#include "atom.h"
#include "atom_vec.h"
#include "comm.h"
#include "domain.h"
#include "error.h"
#include "force.h"
#include "memory.h"
#include "modify.h"
#include "neighbor.h"

#include <cmath>
#include <cstring>

using namespace LAMMPS_NS;
using namespace FixConst;

/* ---------------------------------------------------------------------- */

FixSRP::FixSRP(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
{
  // settings
  nevery=1;
  peratom_freq = 1;
  time_integrate = 0;
  create_attribute = 0;
  comm_border = 2;

  // restart settings
  restart_global = 1;
  restart_peratom = 1;
  restart_pbc = 1;

  // per-atom array width 2
  peratom_flag = 1;
  size_peratom_cols = 2;

  // initial allocation of atom-based array
  // register with Atom class
  array = nullptr;
  grow_arrays(atom->nmax);

  // extends pack_exchange()
  atom->add_callback(Atom::GROW);
  atom->add_callback(Atom::RESTART); // restart
  atom->add_callback(Atom::BORDER);

  // initialize to illegal values so we capture
  btype = -1;
  bptype = -1;

  // zero
  for (int i = 0; i < atom->nmax; i++)
    for (int m = 0; m < 2; m++)
      array[i][m] = 0.0;
}

/* ---------------------------------------------------------------------- */

FixSRP::~FixSRP()
{
  // unregister callbacks to this fix from Atom class
  atom->delete_callback(id,Atom::GROW);
  atom->delete_callback(id,Atom::RESTART);
  atom->delete_callback(id,Atom::BORDER);
  memory->destroy(array);
}

/* ---------------------------------------------------------------------- */

int FixSRP::setmask()
{
  int mask = 0;
  mask |= PRE_FORCE;
  mask |= PRE_EXCHANGE;
  mask |= POST_RUN;

  return mask;
}

/* ---------------------------------------------------------------------- */

void FixSRP::init()
{
  if (force->pair_match("hybrid",1) == nullptr && force->pair_match("hybrid/overlay",1) == nullptr)
    error->all(FLERR,"Cannot use pair srp without pair_style hybrid");

  int has_rigid = 0;
  for (int i = 0; i < modify->nfix; i++)
    if (strncmp(modify->fix[i]->style,"rigid",5) == 0) ++has_rigid;

  if (has_rigid > 0)
    error->all(FLERR,"Pair srp is not compatible with rigid fixes.");

  if ((bptype < 1) || (bptype > atom->ntypes))
    error->all(FLERR,"Illegal bond particle type");

  // this fix must come before any fix which migrates atoms in its pre_exchange()
  // because this fix's pre_exchange() creates per-atom data structure
  // that data must be current for atom migration to carry it along

  for (int i = 0; i < modify->nfix; i++) {
    if (modify->fix[i] == this) break;
    if (modify->fix[i]->pre_exchange_migrate)
      error->all(FLERR,"Fix SRP comes after a fix which "
                 "migrates atoms in pre_exchange");
  }

  // setup neigh exclusions for diff atom types
  // bond particles do not interact with other types
  // type bptype only interacts with itself

  for (int z = 1; z < atom->ntypes; z++) {
    if (z == bptype)
      continue;
    neighbor->modify_params(fmt::format("exclude type {} {}",z,bptype));
  }
}

/* ----------------------------------------------------------------------
   insert bond particles
------------------------------------------------------------------------- */

void FixSRP::setup_pre_force(int /*zz*/)
{
  double **x = atom->x;
  double **xold;
  tagint *tag = atom->tag;
  tagint *tagold;
  int *type = atom->type;
  int* dlist;
  AtomVec *avec = atom->avec;
  int **bondlist = neighbor->bondlist;

  int nlocal, nlocal_old;
  nlocal = nlocal_old = atom->nlocal;
  bigint nall = atom->nlocal + atom->nghost;
  int nbondlist = neighbor->nbondlist;
  int i,j,n;

  // make a copy of all coordinates and tags
  // that is consistent with the bond list as
  // atom->x will be affected by creating/deleting atoms.
  // also compile list of local atoms to be deleted.

  memory->create(xold,nall,3,"fix_srp:xold");
  memory->create(tagold,nall,"fix_srp:tagold");
  memory->create(dlist,nall,"fix_srp:dlist");

  for (i = 0; i < nall; i++) {
    xold[i][0] = x[i][0];
    xold[i][1] = x[i][1];
    xold[i][2] = x[i][2];
    tagold[i]=tag[i];
    dlist[i] = (type[i] == bptype) ? 1 : 0;
    for (n = 0; n < 2; n++)
      array[i][n] = 0.0;
  }

  // delete local atoms flagged in dlist
  i = 0;
  int ndel = 0;
  while (i < nlocal) {
    if (dlist[i]) {
      avec->copy(nlocal-1,i,1);
      dlist[i] = dlist[nlocal-1];
      nlocal--;
      ndel++;
    } else i++;
  }

  atom->nlocal = nlocal;
  memory->destroy(dlist);

  int nadd = 0;
  double rsqold = 0.0;
  double delx, dely, delz, rmax, rsq, rsqmax;
  double xone[3];

  for (n = 0; n < nbondlist; n++) {

    // consider only the user defined bond type
    // btype of zero considers all bonds
    if (btype > 0 && bondlist[n][2] != btype)
      continue;

    i = bondlist[n][0];
    j = bondlist[n][1];

    // position of bond i
    xone[0] = (xold[i][0] + xold[j][0])*0.5;
    xone[1] = (xold[i][1] + xold[j][1])*0.5;
    xone[2] = (xold[i][2] + xold[j][2])*0.5;

    // record longest bond
    // this used to set ghost cutoff
    delx = xold[j][0] - xold[i][0];
    dely = xold[j][1] - xold[i][1];
    delz = xold[j][2] - xold[i][2];
    rsq = delx*delx + dely*dely + delz*delz;
    if (rsq > rsqold) rsqold = rsq;

    // make one particle for each bond
    // i is local
    // if newton bond, always make particle
    // if j is local, always make particle
    // if j is ghost, decide from tag

    if ((force->newton_bond) || (j < nlocal_old) || (tagold[i] > tagold[j])) {
      atom->natoms++;
      avec->create_atom(bptype,xone);
      // pack tag i/j into buffer for comm
      array[atom->nlocal-1][0] = static_cast<double>(tagold[i]);
      array[atom->nlocal-1][1] = static_cast<double>(tagold[j]);
      nadd++;
    }
  }

  bigint nblocal = atom->nlocal;
  MPI_Allreduce(&nblocal,&atom->natoms,1,MPI_LMP_BIGINT,MPI_SUM,world);

  // free temporary storage
  memory->destroy(xold);
  memory->destroy(tagold);

  char str[128];
  int nadd_all = 0, ndel_all = 0;
  MPI_Allreduce(&ndel,&ndel_all,1,MPI_INT,MPI_SUM,world);
  MPI_Allreduce(&nadd,&nadd_all,1,MPI_INT,MPI_SUM,world);
  if (comm->me == 0)
    error->message(FLERR,"Removed/inserted {}/{} bond particles.", ndel_all,nadd_all);

  // check ghost comm distances
  // warn and change if shorter from estimate
  // ghost atoms must be present for bonds on edge of neighbor cutoff
  // extend cutghost slightly more than half of the longest bond
  MPI_Allreduce(&rsqold,&rsqmax,1,MPI_DOUBLE,MPI_MAX,world);
  rmax = sqrt(rsqmax);
  double cutneighmax_srp = neighbor->cutneighmax + 0.51*rmax;

  double length0,length1,length2;
  if (domain->triclinic) {
    double *h_inv = domain->h_inv;
    length0 = sqrt(h_inv[0]*h_inv[0] + h_inv[5]*h_inv[5] + h_inv[4]*h_inv[4]);
    length1 = sqrt(h_inv[1]*h_inv[1] + h_inv[3]*h_inv[3]);
    length2 = h_inv[2];
  } else length0 = length1 = length2 = 1.0;

  // find smallest cutghost.
  // comm->cutghost is stored in fractional coordinates for triclinic
  double cutghostmin = comm->cutghost[0]/length0;
  if (cutghostmin > comm->cutghost[1]/length1)
    cutghostmin = comm->cutghost[1]/length1;
  if (cutghostmin > comm->cutghost[2]/length2)
    cutghostmin = comm->cutghost[2]/length2;

  // stop if cutghost is insufficient
  if (cutneighmax_srp > cutghostmin)
    error->all(FLERR,"Communication cutoff too small for fix srp. "
            "Need {:.8}, current {:.8}", cutneighmax_srp, cutghostmin);

  // assign tags for new atoms, update map
  atom->tag_extend();
  if (atom->map_style != Atom::MAP_NONE) {
    atom->nghost = 0;
    atom->map_init();
    atom->map_set();
  }

  // put new particles in the box before exchange
  // move owned to new procs
  // get ghosts
  // build neigh lists again

  // if triclinic, lambda coords needed for pbc, exchange, borders
  if (domain->triclinic) domain->x2lamda(atom->nlocal);
  domain->pbc();
  comm->setup();
  if (neighbor->style) neighbor->setup_bins();
  comm->exchange();
  if (atom->sortfreq > 0) atom->sort();
  comm->borders();
  // back to box coords
  if (domain->triclinic) domain->lamda2x(atom->nlocal+atom->nghost);
  domain->image_check();
  domain->box_too_small_check();
  modify->setup_pre_neighbor();
  neighbor->build(1);
  neighbor->ncalls = 0;

  // new atom counts

  nlocal = atom->nlocal;
  nall = atom->nlocal + atom->nghost;

  // zero all forces

  for (i = 0; i < nall; i++)
    atom->f[i][0] = atom->f[i][1] = atom->f[i][2] = 0.0;

  // do not include bond particles in thermo output
  // remove them from all groups. set their velocity to zero.

  for (i=0; i< nlocal; i++)
    if (atom->type[i] == bptype) {
      atom->mask[i] = 0;
      atom->v[i][0] = atom->v[i][1] = atom->v[i][2] = 0.0;
    }
}

/* ----------------------------------------------------------------------
   set position of bond particles
------------------------------------------------------------------------- */

void FixSRP::pre_exchange()
{
  // update ghosts
  comm->forward_comm();

  // reassign bond particle coordinates to midpoint of bonds
  // only need to do this before neigh rebuild
  double **x=atom->x;
  int i,j;
  int nlocal = atom->nlocal;

  for (int ii = 0; ii < nlocal; ii++) {
    if (atom->type[ii] != bptype) continue;

    i = atom->map(static_cast<tagint>(array[ii][0]));
    if (i < 0) error->all(FLERR,"Fix SRP failed to map atom");
    i = domain->closest_image(ii,i);

    j = atom->map(static_cast<tagint>(array[ii][1]));
    if (j < 0) error->all(FLERR,"Fix SRP failed to map atom");
    j = domain->closest_image(ii,j);

    // position of bond particle ii
    atom->x[ii][0] = (x[i][0] + x[j][0])*0.5;
    atom->x[ii][1] = (x[i][1] + x[j][1])*0.5;
    atom->x[ii][2] = (x[i][2] + x[j][2])*0.5;
  }
}

/* ----------------------------------------------------------------------
   memory usage of local atom-based array
------------------------------------------------------------------------- */

double FixSRP::memory_usage()
{
  double bytes = (double)atom->nmax*2 * sizeof(double);
  return bytes;
}

/* ----------------------------------------------------------------------
   allocate atom-based array
------------------------------------------------------------------------- */

void FixSRP::grow_arrays(int nmax)
{
  memory->grow(array,nmax,2,"fix_srp:array");
  array_atom = array;
}

/* ----------------------------------------------------------------------
   copy values within local atom-based array
   called when move to new proc
------------------------------------------------------------------------- */

void FixSRP::copy_arrays(int i, int j, int /*delflag*/)
{
  for (int m = 0; m < 2; m++)
    array[j][m] = array[i][m];
}

/* ----------------------------------------------------------------------
   initialize one atom's array values
   called when atom is created
------------------------------------------------------------------------- */

void FixSRP::set_arrays(int i)
{
  array[i][0] = -1;
  array[i][1] = -1;
}

/* ----------------------------------------------------------------------
   pack values in local atom-based array for exchange with another proc
------------------------------------------------------------------------- */

int FixSRP::pack_exchange(int i, double *buf)
{
  for (int m = 0; m < 2; m++) buf[m] = array[i][m];
  return 2;
}

/* ----------------------------------------------------------------------
   unpack values in local atom-based array from exchange with another proc
------------------------------------------------------------------------- */

int FixSRP::unpack_exchange(int nlocal, double *buf)
{
  for (int m = 0; m < 2; m++) array[nlocal][m] = buf[m];
  return 2;
}
/* ----------------------------------------------------------------------
   pack values for border communication at re-neighboring
------------------------------------------------------------------------- */

int FixSRP::pack_border(int n, int *list, double *buf)
{
  // pack buf for border com
  int i,j;
  int m = 0;
    for (i = 0; i < n; i++) {
      j = list[i];
      buf[m++] = array[j][0];
      buf[m++] = array[j][1];
    }
  return m;
}

/* ----------------------------------------------------------------------
   unpack values for border communication at re-neighboring
------------------------------------------------------------------------- */

int FixSRP::unpack_border(int n, int first, double *buf)
{
  // unpack buf into array
  int i,last;
  int m = 0;
  last = first + n;

  for (i = first; i < last; i++) {
    array[i][0] = buf[m++];
    array[i][1] = buf[m++];
  }
  return m;
}

/* ----------------------------------------------------------------------
   remove particles after run
------------------------------------------------------------------------- */

void FixSRP::post_run()
{
  // all bond particles are removed after each run
  // useful for write_data and write_restart commands
  // since those commands occur between runs

  bigint natoms_previous = atom->natoms;
  int nlocal = atom->nlocal;
  int* dlist;
  memory->create(dlist,nlocal,"fix_srp:dlist");

  for (int i = 0; i < nlocal; i++) {
    if (atom->type[i] == bptype)
      dlist[i] = 1;
    else
      dlist[i] = 0;
  }

  // delete local atoms flagged in dlist
  // reset nlocal

  AtomVec *avec = atom->avec;

  int i = 0;
  while (i < nlocal) {
    if (dlist[i]) {
      avec->copy(nlocal-1,i,1);
      dlist[i] = dlist[nlocal-1];
      nlocal--;
    } else i++;
  }

  atom->nlocal = nlocal;
  memory->destroy(dlist);

  // reset atom->natoms
  // reset atom->map if it exists
  // set nghost to 0 so old ghosts won't be mapped

  bigint nblocal = atom->nlocal;
  MPI_Allreduce(&nblocal,&atom->natoms,1,MPI_LMP_BIGINT,MPI_SUM,world);
  if (atom->map_style != Atom::MAP_NONE) {
    atom->nghost = 0;
    atom->map_init();
    atom->map_set();
  }

  // print before and after atom count

  bigint ndelete = natoms_previous - atom->natoms;

  if (comm->me == 0)
    utils::logmesg(lmp,"Deleted {} atoms, new total = {}\n",ndelete,atom->natoms);

  // verlet calls box_too_small_check() in post_run
  // this check maps all bond partners
  // therefore need ghosts

  // need to convert to lambda coords before apply pbc
  if (domain->triclinic) domain->x2lamda(atom->nlocal);
  domain->pbc();
  comm->setup();
  comm->exchange();
  if (atom->sortfreq > 0) atom->sort();
  comm->borders();
  // change back to box coordinates
  if (domain->triclinic) domain->lamda2x(atom->nlocal+atom->nghost);
}

/* ----------------------------------------------------------------------
   pack values in local atom-based arrays for restart file
------------------------------------------------------------------------- */

int FixSRP::pack_restart(int i, double *buf)
{
  int m = 0;
  // pack buf[0] this way because other fixes unpack it
  buf[m++] = 3;
  buf[m++] = array[i][0];
  buf[m++] = array[i][1];
  return m;
}

/* ----------------------------------------------------------------------
   unpack values from atom->extra array to restart the fix
------------------------------------------------------------------------- */

void FixSRP::unpack_restart(int nlocal, int nth)
{
  double **extra = atom->extra;

  // skip to Nth set of extra values
  // unpack the Nth first values this way because other fixes pack them

  int m = 0;
  for (int i = 0; i < nth; i++) {
    m += static_cast<int> (extra[nlocal][m]);
  }

  m++;
  array[nlocal][0] = extra[nlocal][m++];
  array[nlocal][1] = extra[nlocal][m++];

}
/* ----------------------------------------------------------------------
   maxsize of any atom's restart data
------------------------------------------------------------------------- */

int FixSRP::maxsize_restart()
{
  return 3;
}

/* ----------------------------------------------------------------------
   size of atom nlocal's restart data
------------------------------------------------------------------------- */

int FixSRP::size_restart(int /*nlocal*/)
{
  return 3;
}

/* ----------------------------------------------------------------------
   pack global state of Fix
------------------------------------------------------------------------- */

void FixSRP::write_restart(FILE *fp)
{
  int n = 0;
  double list[3];
  list[n++] = comm->cutghostuser;
  list[n++] = btype;
  list[n++] = bptype;

  if (comm->me == 0) {
    int size = n * sizeof(double);
    fwrite(&size,sizeof(int),1,fp);
    fwrite(list,sizeof(double),n,fp);
  }
}

/* ----------------------------------------------------------------------
   use info from restart file to restart the Fix
------------------------------------------------------------------------- */

void FixSRP::restart(char *buf)
{
  int n = 0;
  double *list = (double *) buf;

  comm->cutghostuser = static_cast<double> (list[n++]);
  btype = static_cast<int> (list[n++]);
  bptype = static_cast<int> (list[n++]);
}

/* ----------------------------------------------------------------------
   interface with pair class
   pair srp sets the bond type in this fix
------------------------------------------------------------------------- */

int FixSRP::modify_param(int /*narg*/, char **arg)
{
  if (strcmp(arg[0],"btype") == 0) {
    btype = utils::inumeric(FLERR,arg[1],false,lmp);
    return 2;
  }
  if (strcmp(arg[0],"bptype") == 0) {
    bptype = utils::inumeric(FLERR,arg[1],false,lmp);
    return 2;
  }
  return 0;
}