proof-of-concept implementation for neighbor list based balancing with yet unsolved problems

#include "error.h"

#include "comm.h"

#include "force.h"

#include "neighbor.h"

#include "neigh_request.h"

#include "neigh_list.h"

using namespace LAMMPS_NS;

void ImbalanceNeigh::compute(double *weight)

{

  const int nlocal = _lmp->atom->nlocal;

  MPI_Comm world = _lmp->world;

  // find suitable existing neighbor list

  Error *error = _lmp->error;

  Neighbor *neighbor = _lmp->neighbor;

  int req;

  // we can only make use of certain (conventional) neighbor lists.

  for (req = 0; req < neighbor->old_nrequest; ++req) {

    if ((neighbor->old_requests[req]->half ||

         neighbor->old_requests[req]->gran ||

         neighbor->old_requests[req]->respaouter ||

         neighbor->old_requests[req]->half_from_full) &&

        neighbor->old_requests[req]->skip == 0 &&

        neighbor->lists[req] && neighbor->lists[req]->numneigh) break;

  }

  if (req >= neighbor->old_nrequest) {

    if (_lmp->comm->me == 0)

      error->warning(FLERR,"No suitable neighbor list for balancing found");

    return;

  }

  if (_factor > 0.0) {

    MPI_Comm world = _lmp->world;

    NeighList *list = neighbor->lists[req];

    bigint neighsum = 0;

    const int inum = list->inum;

    const int * const ilist = list->ilist;

    const int * const numneigh = list->numneigh;

    // first pass: get local number of neighbors.

    for (int i = 0; i < inum; ++i) neighsum += numneigh[ilist[i]];

    double allavg, myavg = ((double) neighsum)/((double) _lmp->atom->natoms);

    MPI_Allreduce(&myavg,&allavg,1,MPI_DOUBLE,MPI_SUM,world);

    double scale = 1.0/allavg;

    // second pass: compute and apply weights

    for (int ii = 0; ii < inum; ++ii) {

      const int i = ilist[ii];

      weight[i] *= (1.0-_factor) + _factor*scale*numneigh[i];

    }

  }

}

#include "imbalance_var.h"

#include "atom.h"

#include "error.h"

#include "force.h"

#include "group.h"

#include "input.h"

#include "variable.h"

int ImbalanceVar::options(int narg, char **arg)

{

  Error *error = _lmp->error;

  Force *force = _lmp->force;

  if (narg < 1) error->all(FLERR,"Illegal balance weight command");

  int len = strlen(arg[0])+1;