/* ----------------------------------------------------------------------
   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: Andres Jaramillo-Botero
------------------------------------------------------------------------- */

#include "mpi.h"
#include "math.h"
#include "compute_ke_eff.h"
#include "atom.h"
#include "update.h"
#include "force.h"
#include "domain.h"
#include "group.h"
#include "error.h"

using namespace LAMMPS_NS;

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

ComputeKEEff::ComputeKEEff(LAMMPS *lmp, int narg, char **arg) :
  Compute(lmp, narg, arg)
{
  if (narg != 3) error->all("Illegal compute ke/eff command");

  scalar_flag = 1;
  extscalar = 1;

  // error check

  if (!atom->ervel_flag) 
    error->all("Compute ke/eff requires atom attribute ervel");
}

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

void ComputeKEEff::init()
{
  pfactor = 0.5 * force->mvv2e;
}

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

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

  double **v = atom->v;
  double *ervel = atom->ervel;
  double *mass = atom->mass;
  int *spin = atom->spin;
  int *mask = atom->mask;
  int *type = atom->type;
  int nlocal = atom->nlocal;

  double ke = 0.0;

  if (mass) {
    for (int i = 0; i < nlocal; i++)
      if (mask[i] & groupbit) {
        ke += mass[type[i]]*(v[i][0]*v[i][0] + v[i][1]*v[i][1] + 
                             v[i][2]*v[i][2]);
        if (fabs(spin[i])==1) ke += 0.75*mass[type[i]]*ervel[i]*ervel[i];
      }
  }

  MPI_Allreduce(&ke,&scalar,1,MPI_DOUBLE,MPI_SUM,world);
  scalar *= pfactor;
  return scalar;
}