/* ----------------------------------------------------------------------
    This is the

    ██╗     ██╗ ██████╗  ██████╗  ██████╗ ██╗  ██╗████████╗███████╗
    ██║     ██║██╔════╝ ██╔════╝ ██╔════╝ ██║  ██║╚══██╔══╝██╔════╝
    ██║     ██║██║  ███╗██║  ███╗██║  ███╗███████║   ██║   ███████╗
    ██║     ██║██║   ██║██║   ██║██║   ██║██╔══██║   ██║   ╚════██║
    ███████╗██║╚██████╔╝╚██████╔╝╚██████╔╝██║  ██║   ██║   ███████║
    ╚══════╝╚═╝ ╚═════╝  ╚═════╝  ╚═════╝ ╚═╝  ╚═╝   ╚═╝   ╚══════╝®

    DEM simulation engine, released by
    DCS Computing Gmbh, Linz, Austria
    http://www.dcs-computing.com, office@dcs-computing.com

    LIGGGHTS® is part of CFDEM®project:
    http://www.liggghts.com | http://www.cfdem.com

    Core developer and main author:
    Christoph Kloss, christoph.kloss@dcs-computing.com

    LIGGGHTS® is open-source, distributed under the terms of the GNU Public
    License, version 2 or later. It is distributed in the hope that it will
    be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. You should have
    received a copy of the GNU General Public License along with LIGGGHTS®.
    If not, see http://www.gnu.org/licenses . See also top-level README
    and LICENSE files.

    LIGGGHTS® and CFDEM® are registered trade marks of DCS Computing GmbH,
    the producer of the LIGGGHTS® software and the CFDEM®coupling software
    See http://www.cfdem.com/terms-trademark-policy for details.

-------------------------------------------------------------------------
    Contributing author and copyright for this file:
    This file is from LAMMPS
    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.
------------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
Contributing authors for SPH:
Andreas Eitzlmayr (Institute for Process and Particle Engineering, TU Graz)
andreas.eitzlmayr@tugraz.at
Christoph Kloss (DCS)
------------------------------------------------------------------------- */

#include <string.h>
#include <stdlib.h>
#include "compute_reduce.h"
#include "atom.h"
#include "update.h"
#include "domain.h"
#include "modify.h"
#include "fix.h"
#include "force.h"
#include "comm.h"
#include "group.h"
#include "input.h"
#include "variable.h"
#include "memory.h"
#include "error.h"

using namespace LAMMPS_NS;

enum{SUM,MINN,MAXX,AVE};
enum{X,V,F,COMPUTE,FIX,VARIABLE,RHO,P}; 
enum{PERATOM,LOCAL};

#define BIG 1.0e20

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

ComputeReduce::ComputeReduce(LAMMPS *lmp, int &iarg, int narg, char **arg) :
  Compute(lmp, iarg, narg, arg)
{
  if (strcmp(style,"reduce") == 0) {
    if (narg < iarg+2) error->all(FLERR,"Illegal compute reduce command");
    idregion = NULL;
  } else if (strcmp(style,"reduce/region") == 0) {
    if (narg < iarg+3) error->all(FLERR,"Illegal compute reduce/region command");
    iregion = domain->find_region(arg[iarg]);
    if (iregion == -1)
      error->all(FLERR,"Region ID for compute reduce/region does not exist");
    int n = strlen(arg[iarg]) + 1;
    idregion = new char[n];
    strcpy(idregion,arg[iarg]);
    iarg++;
  } else error->all(FLERR,"Illegal compute reduce command: invalid style");

  if (strcmp(arg[iarg],"sum") == 0) mode = SUM;
  else if (strcmp(arg[iarg],"min") == 0) mode = MINN;
  else if (strcmp(arg[iarg],"max") == 0) mode = MAXX;
  else if (strcmp(arg[iarg],"ave") == 0) mode = AVE;
  else error->all(FLERR,"Illegal compute reduce command");
  iarg++;

  MPI_Comm_rank(world,&me);

  // parse remaining values until one isn't recognized

  which = new int[narg-iarg];
  argindex = new int[narg-iarg];
  flavor = new int[narg-iarg];
  ids = new char*[narg-iarg];
  value2index = new int[narg-iarg];
  nvalues = 0;

  while (iarg < narg) {
    ids[nvalues] = NULL;

    if (strcmp(arg[iarg],"x") == 0) {
      which[nvalues] = X;
      argindex[nvalues++] = 0;
    } else if (strcmp(arg[iarg],"y") == 0) {
      which[nvalues] = X;
      argindex[nvalues++] = 1;
    } else if (strcmp(arg[iarg],"z") == 0) {
      which[nvalues] = X;
      argindex[nvalues++] = 2;

    } else if (strcmp(arg[iarg],"vx") == 0) {
      which[nvalues] = V;
      argindex[nvalues++] = 0;
    } else if (strcmp(arg[iarg],"vy") == 0) {
      which[nvalues] = V;
      argindex[nvalues++] = 1;
    } else if (strcmp(arg[iarg],"vz") == 0) {
      which[nvalues] = V;
      argindex[nvalues++] = 2;

    } else if (strcmp(arg[iarg],"fx") == 0) {
      which[nvalues] = F;
      argindex[nvalues++] = 0;
    } else if (strcmp(arg[iarg],"fy") == 0) {
      which[nvalues] = F;
      argindex[nvalues++] = 1;
    } else if (strcmp(arg[iarg],"fz") == 0) {
      which[nvalues] = F;
      argindex[nvalues++] = 2;

    } else if (strcmp(arg[iarg],"rho") == 0) { 
      which[nvalues] = RHO;
      argindex[nvalues++] = 0;
    } else if (strcmp(arg[iarg],"p") == 0) {
      which[nvalues] = P;
      argindex[nvalues++] = 0;

    } else if (strncmp(arg[iarg],"c_",2) == 0 ||
               strncmp(arg[iarg],"f_",2) == 0 ||
               strncmp(arg[iarg],"v_",2) == 0) {
      if (arg[iarg][0] == 'c') which[nvalues] = COMPUTE;
      else if (arg[iarg][0] == 'f') which[nvalues] = FIX;
      else if (arg[iarg][0] == 'v') which[nvalues] = VARIABLE;

      int n = strlen(arg[iarg]);
      char *suffix = new char[n];
      strcpy(suffix,&arg[iarg][2]);

      char *ptr = strchr(suffix,'[');
      if (ptr) {
        if (suffix[strlen(suffix)-1] != ']')
          error->all(FLERR,"Illegal compute reduce command");
        argindex[nvalues] = atoi(ptr+1);
        *ptr = '\0';
      } else argindex[nvalues] = 0;

      n = strlen(suffix) + 1;
      ids[nvalues] = new char[n];
      strcpy(ids[nvalues],suffix);
      nvalues++;
      delete [] suffix;

    } else break;

    iarg++;
  }

  // optional args

  replace = new int[nvalues];
  for (int i = 0; i < nvalues; i++) replace[i] = -1;

  while (iarg < narg) {
    if (strcmp(arg[iarg],"replace") == 0) {
      if (iarg+3 > narg) error->all(FLERR,"Illegal compute reduce command");
      if (mode != MINN && mode != MAXX)
        error->all(FLERR,"Compute reduce replace requires min or max mode");
      int col1 = atoi(arg[iarg+1]) - 1;
      int col2 = atoi(arg[iarg+2]) - 1;
      if (col1 < 0 || col1 >= nvalues || col2 < 0 || col2 >= nvalues)
        error->all(FLERR,"Illegal compute reduce command");
      if (col1 == col2) error->all(FLERR,"Illegal compute reduce command");
      if (replace[col1] >= 0 || replace[col2] >= 0)
        error->all(FLERR,"Invalid replace values in compute reduce");
      replace[col1] = col2;
      iarg += 3;
    } else error->all(FLERR,"Illegal compute reduce command");
  }

  // delete replace if not set

  int flag = 0;
  for (int i = 0; i < nvalues; i++)
    if (replace[i] >= 0) flag = 1;
  if (!flag) {
    delete [] replace;
    replace = NULL;
  }

  // setup and error check

  for (int i = 0; i < nvalues; i++) {
    if (which[i] == X || which[i] == V || which[i] == F)
      flavor[i] = PERATOM;

    else if (which[i] == COMPUTE) {
      int icompute = modify->find_compute(ids[i]);
      if (icompute < 0)
        error->all(FLERR,"Compute ID for compute reduce does not exist");
      if (modify->compute[icompute]->peratom_flag) {
        flavor[i] = PERATOM;
        if (argindex[i] == 0 &&
            modify->compute[icompute]->size_peratom_cols != 0)
          error->all(FLERR,"Compute reduce compute does not "
                     "calculate a per-atom vector");
        if (argindex[i] && modify->compute[icompute]->size_peratom_cols == 0)
          error->all(FLERR,"Compute reduce compute does not "
                     "calculate a per-atom array");
        if (argindex[i] &&
            argindex[i] > modify->compute[icompute]->size_peratom_cols)
          error->all(FLERR,
                     "Compute reduce compute array is accessed out-of-range");
      } else if (modify->compute[icompute]->local_flag) {
        flavor[i] = LOCAL;
        if (argindex[i] == 0 &&
            modify->compute[icompute]->size_local_cols != 0)
          error->all(FLERR,"Compute reduce compute does not "
                     "calculate a local vector");
        if (argindex[i] && modify->compute[icompute]->size_local_cols == 0)
          error->all(FLERR,"Compute reduce compute does not "
                     "calculate a local array");
        if (argindex[i] &&
            argindex[i] > modify->compute[icompute]->size_local_cols)
          error->all(FLERR,
                     "Compute reduce compute array is accessed out-of-range");
      } else error->all(FLERR,
                        "Compute reduce compute calculates global values");

    } else if (which[i] == FIX) {
      int ifix = modify->find_fix(ids[i]);
      if (ifix < 0)
        error->all(FLERR,"Fix ID for compute reduce does not exist");
      if (modify->fix[ifix]->peratom_flag) {
        flavor[i] = PERATOM;
        if (argindex[i] == 0 &&
            modify->fix[ifix]->size_peratom_cols != 0)
          error->all(FLERR,"Compute reduce fix does not "
                     "calculate a per-atom vector");
        if (argindex[i] && modify->fix[ifix]->size_peratom_cols == 0)
          error->all(FLERR,"Compute reduce fix does not "
                     "calculate a per-atom array");
        if (argindex[i] &&
            argindex[i] > modify->fix[ifix]->size_peratom_cols)
          error->all(FLERR,"Compute reduce fix array is accessed out-of-range");
      } else if (modify->fix[ifix]->local_flag) {
        flavor[i] = LOCAL;
        if (argindex[i] == 0 &&
            modify->fix[ifix]->size_local_cols != 0)
          error->all(FLERR,"Compute reduce fix does not "
                     "calculate a local vector");
        if (argindex[i] && modify->fix[ifix]->size_local_cols == 0)
          error->all(FLERR,"Compute reduce fix does not "
                     "calculate a local array");
        if (argindex[i] &&
            argindex[i] > modify->fix[ifix]->size_local_cols)
          error->all(FLERR,"Compute reduce fix array is accessed out-of-range");
      } else error->all(FLERR,"Compute reduce fix calculates global values");

    } else if (which[i] == VARIABLE) {
      int ivariable = input->variable->find(ids[i]);
      if (ivariable < 0)
        error->all(FLERR,"Variable name for compute reduce does not exist");
      if (input->variable->atomstyle(ivariable) == 0)
        error->all(FLERR,"Compute reduce variable is not atom-style variable");
      flavor[i] = PERATOM;
    }
  }

  // this compute produces either a scalar or vector

  if (nvalues == 1) {
    scalar_flag = 1;
    if (mode == SUM) extscalar = 1;
    else extscalar = 0;
    vector = onevec = NULL;
    indices = owner = NULL;
  } else {
    vector_flag = 1;
    size_vector = nvalues;
    if (mode == SUM) extvector = 1;
    else extvector = 0;
    vector = new double[size_vector];
    onevec = new double[size_vector];
    indices = new int[size_vector];
    owner = new int[size_vector];
  }

  maxatom = 0;
  varatom = NULL;
}

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

ComputeReduce::~ComputeReduce()
{
  delete [] which;
  delete [] argindex;
  delete [] flavor;
  for (int m = 0; m < nvalues; m++) delete [] ids[m];
  delete [] ids;
  delete [] value2index;
  delete [] replace;
  delete [] idregion;

  delete [] vector;
  delete [] onevec;
  delete [] indices;
  delete [] owner;

  memory->destroy(varatom);
}

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

void ComputeReduce::init()
{
  // set indices of all computes,fixes,variables

  for (int m = 0; m < nvalues; m++) {
    if (which[m] == COMPUTE) {
      int icompute = modify->find_compute(ids[m]);
      if (icompute < 0)
        error->all(FLERR,"Compute ID for compute reduce does not exist");
      value2index[m] = icompute;

    } else if (which[m] == FIX) {
      int ifix = modify->find_fix(ids[m]);
      if (ifix < 0)
        error->all(FLERR,"Fix ID for compute reduce does not exist");
      value2index[m] = ifix;

    } else if (which[m] == VARIABLE) {
      int ivariable = input->variable->find(ids[m]);
      if (ivariable < 0)
        error->all(FLERR,"Variable name for compute reduce does not exist");
      value2index[m] = ivariable;

    } else value2index[m] = -1;
  }

  // set index and check validity of region

  if (idregion) {
    iregion = domain->find_region(idregion);
    if (iregion == -1)
      error->all(FLERR,"Region ID for compute reduce/region does not exist");
  }
}

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

double ComputeReduce::compute_scalar()
{
  invoked_scalar = update->ntimestep;

  double one = compute_one(0,-1);

  if (mode == SUM) {
    MPI_Allreduce(&one,&scalar,1,MPI_DOUBLE,MPI_SUM,world);
  } else if (mode == MINN) {
    MPI_Allreduce(&one,&scalar,1,MPI_DOUBLE,MPI_MIN,world);
  } else if (mode == MAXX) {
    MPI_Allreduce(&one,&scalar,1,MPI_DOUBLE,MPI_MAX,world);
  } else if (mode == AVE) {
    MPI_Allreduce(&one,&scalar,1,MPI_DOUBLE,MPI_SUM,world);
    bigint n = count(0);
    if (n) scalar /= n;
  }

  return scalar;
}

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

void ComputeReduce::compute_vector()
{
  invoked_vector = update->ntimestep;

  for (int m = 0; m < nvalues; m++)
    if (!replace || replace[m] < 0) {
      onevec[m] = compute_one(m,-1);
      indices[m] = index;
    }

  if (mode == SUM) {
    for (int m = 0; m < nvalues; m++)
      MPI_Allreduce(&onevec[m],&vector[m],1,MPI_DOUBLE,MPI_SUM,world);

  } else if (mode == MINN) {
    if (!replace) {
      for (int m = 0; m < nvalues; m++)
        MPI_Allreduce(&onevec[m],&vector[m],1,MPI_DOUBLE,MPI_MIN,world);

    } else {
      for (int m = 0; m < nvalues; m++)
        if (replace[m] < 0) {
          pairme.value = onevec[m];
          pairme.proc = me;
          MPI_Allreduce(&pairme,&pairall,1,MPI_DOUBLE_INT,MPI_MINLOC,world);
          vector[m] = pairall.value;
          owner[m] = pairall.proc;
        }
      for (int m = 0; m < nvalues; m++)
        if (replace[m] >= 0) {
          if (me == owner[replace[m]])
            vector[m] = compute_one(m,indices[replace[m]]);
          MPI_Bcast(&vector[m],1,MPI_DOUBLE,owner[replace[m]],world);
        }
    }

  } else if (mode == MAXX) {
    if (!replace) {
      for (int m = 0; m < nvalues; m++)
        MPI_Allreduce(&onevec[m],&vector[m],1,MPI_DOUBLE,MPI_MAX,world);

    } else {
      for (int m = 0; m < nvalues; m++)
        if (replace[m] < 0) {
          pairme.value = onevec[m];
          pairme.proc = me;
          MPI_Allreduce(&pairme,&pairall,1,MPI_DOUBLE_INT,MPI_MAXLOC,world);
          vector[m] = pairall.value;
          owner[m] = pairall.proc;
        }
      for (int m = 0; m < nvalues; m++)
        if (replace[m] >= 0) {
          if (me == owner[replace[m]])
            vector[m] = compute_one(m,indices[replace[m]]);
          MPI_Bcast(&vector[m],1,MPI_DOUBLE,owner[replace[m]],world);
        }
    }

  } else if (mode == AVE) {
    for (int m = 0; m < nvalues; m++) {
      MPI_Allreduce(&onevec[m],&vector[m],1,MPI_DOUBLE,MPI_SUM,world);
      bigint n = count(m);
      if (n) vector[m] /= n;
    }
  }
}

/* ----------------------------------------------------------------------
   calculate reduced value for one input M and return it
   if flag = -1:
     sum/min/max/ave all values in vector
     for per-atom quantities, limit to atoms in group
     if mode = MIN or MAX, also set index to which vector value wins
   if flag >= 0: simply return vector[flag]
------------------------------------------------------------------------- */

double ComputeReduce::compute_one(int m, int flag)
{
  int i;

  // invoke the appropriate attribute,compute,fix,variable
  // for flag = -1, compute scalar quantity by scanning over atom properties
  // only include atoms in group for atom properties and per-atom quantities

  index = -1;
  int vidx = value2index[m];
  int aidx = argindex[m];

  int *mask = atom->mask;
  int nlocal = atom->nlocal;

  double one = 0.0;
  if (mode == SUM) one = 0.0;
  else if (mode == MINN) one = BIG;
  else if (mode == MAXX) one = -BIG;
  else if (mode == AVE) one = 0.0;

  if (which[m] == X) {
    double **x = atom->x;
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,x[i][aidx],i);
    } else one = x[flag][aidx];
  } else if (which[m] == V) {
    double **v = atom->v;
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,v[i][aidx],i);
    } else one = v[flag][aidx];
  } else if (which[m] == F) {
    double **f = atom->f;
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,f[i][aidx],i);
    } else one = f[flag][aidx];
  } else if (which[m] == RHO) { 
    double *rho = atom->rho;
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,rho[i],i);
    } else one = rho[flag];
  } else if (which[m] == P) { 
    double *p = atom->p;
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,p[i],i);
    } else one = p[flag];

  // invoke compute if not previously invoked

  } else if (which[m] == COMPUTE) {
    Compute *compute = modify->compute[vidx];

    if (flavor[m] == PERATOM) {
      if (!(compute->invoked_flag & INVOKED_PERATOM)) {
        compute->compute_peratom();
        compute->invoked_flag |= INVOKED_PERATOM;
      }

      if (aidx == 0) {
        double *comp_vec = compute->vector_atom;
        int n = nlocal;
        if (flag < 0) {
          for (i = 0; i < n; i++)
            if (mask[i] & groupbit) combine(one,comp_vec[i],i);
        } else one = comp_vec[flag];
      } else {
        double **carray_atom = compute->array_atom;
        int n = nlocal;
        int aidxm1 = aidx - 1;
        if (flag < 0) {
          for (i = 0; i < n; i++)
            if (mask[i] & groupbit) combine(one,carray_atom[i][aidxm1],i);
        } else one = carray_atom[flag][aidxm1];
      }

    } else if (flavor[m] == LOCAL) {
      if (!(compute->invoked_flag & INVOKED_LOCAL)) {
        compute->compute_local();
        compute->invoked_flag |= INVOKED_LOCAL;
      }

      if (aidx == 0) {
        double *comp_vec = compute->vector_local;
        int n = compute->size_local_rows;
        if (flag < 0)
          for (i = 0; i < n; i++)
            combine(one,comp_vec[i],i);
        else one = comp_vec[flag];
      } else {
        double **carray_local = compute->array_local;
        int n = compute->size_local_rows;
        int aidxm1 = aidx - 1;
        if (flag < 0)
          for (i = 0; i < n; i++)
            combine(one,carray_local[i][aidxm1],i);
        else one = carray_local[flag][aidxm1];
      }
    }

  // access fix fields, check if fix frequency is a match

  } else if (which[m] == FIX) {
    if (update->ntimestep % modify->fix[vidx]->peratom_freq)
      error->all(FLERR,"Fix used in compute reduce not computed at compatible time");
    Fix *fix = modify->fix[vidx];

    if (flavor[m] == PERATOM) {
      if (aidx == 0) {
        double *fix_vector = fix->vector_atom;
        int n = nlocal;
        if (flag < 0) {
          for (i = 0; i < n; i++)
            if (mask[i] & groupbit) combine(one,fix_vector[i],i);
        } else one = fix_vector[flag];
      } else {
        double **fix_array = fix->array_atom;
        int aidxm1 = aidx - 1;
        if (flag < 0) {
          for (i = 0; i < nlocal; i++)
            if (mask[i] & groupbit) combine(one,fix_array[i][aidxm1],i);
        } else one = fix_array[flag][aidxm1];
      }

    } else if (flavor[m] == LOCAL) {
      if (aidx == 0) {
        double *fix_vector = fix->vector_local;
        int n = fix->size_local_rows;
        if (flag < 0)
          for (i = 0; i < n; i++)
            combine(one,fix_vector[i],i);
        else one = fix_vector[flag];
      } else {
        double **fix_array = fix->array_local;
        int n = fix->size_local_rows;
        int aidxm1 = aidx - 1;
        if (flag < 0)
          for (i = 0; i < n; i++)
            combine(one,fix_array[i][aidxm1],i);
        else one = fix_array[flag][aidxm1];
      }
    }

  // evaluate atom-style variable

  } else if (which[m] == VARIABLE) {
    if (nlocal > maxatom) {
      maxatom = atom->nmax;
      memory->destroy(varatom);
      memory->create(varatom,maxatom,"reduce:varatom");
    }

    input->variable->compute_atom(vidx,igroup,varatom,1,0);
    if (flag < 0) {
      for (i = 0; i < nlocal; i++)
        if (mask[i] & groupbit) combine(one,varatom[i],i);
    } else one = varatom[flag];
  }

  return one;
}

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

bigint ComputeReduce::count(int m)
{
  int vidx = value2index[m];

  if (which[m] == X || which[m] == V || which[m] == F)
    return group->count(igroup);
  else if (which[m] == COMPUTE) {
    Compute *compute = modify->compute[vidx];
    if (flavor[m] == PERATOM) {
      return group->count(igroup);
    } else if (flavor[m] == LOCAL) {
      bigint ncount = compute->size_local_rows;
      bigint ncountall;
      MPI_Allreduce(&ncount,&ncountall,1,MPI_LMP_BIGINT,MPI_SUM,world);
      return ncountall;
    }
  } else if (which[m] == FIX) {
    Fix *fix = modify->fix[vidx];
    if (flavor[m] == PERATOM) {
      return group->count(igroup);
    } else if (flavor[m] == LOCAL) {
      bigint ncount = fix->size_local_rows;
      bigint ncountall;
      MPI_Allreduce(&ncount,&ncountall,1,MPI_LMP_BIGINT,MPI_SUM,world);
      return ncountall;
    }
  } else if (which[m] == VARIABLE)
    return group->count(igroup);

  bigint dummy = 0;
  return dummy;
}

/* ----------------------------------------------------------------------
   combine two values according to reduction mode
   for MIN/MAX, also update index with winner
------------------------------------------------------------------------- */

void ComputeReduce::combine(double &one, double two, int i)
{
  if (mode == SUM || mode == AVE) one += two;
  else if (mode == MINN) {
    if (two < one) {
      one = two;
      index = i;
    }
  } else if (mode == MAXX) {
    if (two > one) {
      one = two;
      index = i;
    }
  }
}

/* ----------------------------------------------------------------------
   memory usage of varatom
------------------------------------------------------------------------- */

double ComputeReduce::memory_usage()
{
  double bytes = maxatom * sizeof(double);
  return bytes;
}