/* ----------------------------------------------------------------------
   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 authors: German Samolyuk (ORNL) and
                         Mario Pinto (Computational Research Lab, Pune, India)
------------------------------------------------------------------------- */

#include "math.h"
#include "string.h"
#include "compute_charge_flux.h"
#include "atom.h"
#include "update.h"
#include "modify.h"
#include "velocity.h"
#include "group.h"
#include "error.h"

using namespace LAMMPS_NS;


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

ComputeChargeFlux::ComputeChargeFlux(LAMMPS *lmp, int narg, char **arg) :
  Compute(lmp, narg, arg)
{
  if (narg < 3) error->all(FLERR,"Illegal compute charge/flux command");

  vector_flag = 1;
  size_vector = 3;
  extvector = 1;

 
  vector = new double[3];
}

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

ComputeChargeFlux::~ComputeChargeFlux()
{
   delete [] vector;
}

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

void ComputeChargeFlux::init()
{
  
}

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

void ComputeChargeFlux::compute_vector()
{
  invoked_vector = update->ntimestep;
  
  double **v = atom->v;
  double *q = atom->q;
  int *mask = atom->mask;
  int nlocal = atom->nlocal;

  double qi,vx,vy,vz;
  double je[3];
  je[0] = je[1] = je[2]=0.0;

  for (int i = 0; i < nlocal; i++) {
    if (mask[i] & groupbit) {
      qi = q[i]; 
      vx = v[i][0];
      vy = v[i][1];
      vz = v[i][2];
      je[0] += qi * vx;
      je[1] += qi * vy;
      je[2] += qi * vz;
    }
  }

 
  // sum across all procs
  // 1st 3 terms are total charge flux
 

  
  MPI_Allreduce(je,vector,3,MPI_DOUBLE,MPI_SUM,world);
}