/*----------------------------------------------------------------------
  PuReMD - Purdue ReaxFF Molecular Dynamics Program

  Copyright (2010) Purdue University
  Hasan Metin Aktulga, hmaktulga@lbl.gov
  Joseph Fogarty, jcfogart@mail.usf.edu
  Sagar Pandit, pandit@usf.edu
  Ananth Y Grama, ayg@cs.purdue.edu

  Please cite the related publication:
  H. M. Aktulga, J. C. Fogarty, S. A. Pandit, A. Y. Grama,
  "Parallel Reactive Molecular Dynamics: Numerical Methods and
  Algorithmic Techniques", Parallel Computing, in press.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program 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.
  See the GNU General Public License for more details:
  <http://www.gnu.org/licenses/>.
  ----------------------------------------------------------------------*/

#include "pair_reaxc.h"
#include "reaxc_traj.h"
#include "reaxc_list.h"
#include "reaxc_tool_box.h"

int Reallocate_Output_Buffer( output_controls *out_control, int req_space,
                              MPI_Comm comm )
{
  if( out_control->buffer_len > 0 )
    free( out_control->buffer );

  out_control->buffer_len = (int)(req_space*SAFE_ZONE);
  out_control->buffer = (char*) malloc(out_control->buffer_len*sizeof(char));
  if( out_control->buffer == NULL ) {
    fprintf( stderr,
             "insufficient memory for required buffer size %d. terminating!\n",
             (int) (req_space*SAFE_ZONE) );
    MPI_Abort( comm, INSUFFICIENT_MEMORY );
  }

  return SUCCESS;
}


void Write_Skip_Line( output_controls *out_control, mpi_datatypes *mpi_data,
                      int my_rank, int skip, int num_section )
{
  if( my_rank == MASTER_NODE )
    fprintf( out_control->strj, INT2_LINE,
             "chars_to_skip_section:", skip, num_section );
}


int Write_Header( reax_system *system, control_params *control,
                  output_controls *out_control, mpi_datatypes *mpi_data )
{
  int  num_hdr_lines, my_hdr_lines, buffer_req;
  char ensembles[ens_N][25] =  { "NVE", "NVT", "fully flexible NPT",
                                 "semi isotropic NPT", "isotropic NPT" };
  char reposition[3][25] = { "fit to periodic box", "CoM to center of box",
                             "CoM to origin" };
  char t_regime[3][25] = { "T-coupling only", "step-wise", "constant slope" };

  char traj_methods[TF_N][10] = { "custom", "xyz" };
  char atom_formats[8][40] =  { "none", "invalid", "invalid", "invalid",
                                "xyz_q",
                                "xyz_q_fxfyfz",
                                "xyz_q_vxvyvz",
                                "detailed_atom_info" };
  char bond_formats[3][30] = { "none",
                               "basic_bond_info",
                               "detailed_bond_info" };
  char angle_formats[2][30] = { "none", "basic_angle_info" };

  /* set header lengths */
  num_hdr_lines = NUM_HEADER_LINES;
  my_hdr_lines = num_hdr_lines * ( system->my_rank == MASTER_NODE );
  buffer_req = my_hdr_lines * HEADER_LINE_LEN;
  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  /* only the master node writes into trajectory header */
  if( system->my_rank == MASTER_NODE ) {
    /* clear the contents of line & buffer */
    out_control->line[0] = 0;
    out_control->buffer[0] = 0;

    /* to skip the header */
    sprintf( out_control->line, INT_LINE, "chars_to_skip_header:",
             (num_hdr_lines-1) * HEADER_LINE_LEN );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* general simulation info */
    sprintf( out_control->line, STR_LINE, "simulation_name:",
             out_control->traj_title );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, BIGINT_LINE, "number_of_atoms:", system->bigN );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "ensemble_type:",
             ensembles[ control->ensemble ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "number_of_steps:",
             control->nsteps );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "timestep_length_(in_fs):",
             control->dt * 1000 );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* restart info */
    sprintf( out_control->line, STR_LINE, "is_this_a_restart?:",
             (control->restart ? "yes" : "no") );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "write_restart_files?:",
             ((out_control->restart_freq > 0) ? "yes" : "no") );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "frequency_to_write_restarts:",
             out_control->restart_freq );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* preferences */
    sprintf( out_control->line, STR_LINE, "tabulate_long_range_intrs?:",
             (control->tabulate ? "yes" : "no") );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "table_size:", control->tabulate );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "restrict_bonds?:",
             (control->restrict_bonds ? "yes" : "no") );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "bond_restriction_length:",
             control->restrict_bonds );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "reposition_atoms?:",
             reposition[control->reposition_atoms] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "remove_CoM_velocity?:",
             (control->ensemble==NVE) ? 0 : control->remove_CoM_vel);
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );


    /* cut-off values */
    sprintf( out_control->line, REAL_LINE, "bonded_intr_dist_cutoff:",
             control->bond_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "nonbonded_intr_dist_cutoff:",
             control->nonb_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "hbond_dist_cutoff:",
             control->hbond_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "reax_bond_threshold:",
             control->bo_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "physical_bond_threshold:",
             control->bg_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "valence_angle_threshold:",
             control->thb_cut );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, SCI_LINE, "QEq_tolerance:", control->q_err );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* temperature controls */
    sprintf( out_control->line, REAL_LINE, "initial_temperature:",
             control->T_init );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "target_temperature:",
             control->T_final );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "thermal_inertia:",
             control->Tau_T );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "temperature_regime:",
             t_regime[ control->T_mode ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "temperature_change_rate_(K/ps):",
             control->T_rate / control->T_freq );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* pressure controls */
    sprintf( out_control->line, REAL3_LINE, "target_pressure_(GPa):",
             control->P[0], control->P[1], control->P[2] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL3_LINE, "virial_inertia:",
             control->Tau_P[0], control->Tau_P[1], control->Tau_P[2] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* trajectory */
    sprintf( out_control->line, INT_LINE, "energy_dumping_freq:",
             out_control->energy_update_freq );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "trajectory_dumping_freq:",
             out_control->write_steps );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "compress_trajectory_output?:",
             (out_control->traj_compress ? "yes" : "no") );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "trajectory_format:",
             traj_methods[ out_control->traj_method ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "atom_info:",
             atom_formats[ out_control->atom_info ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "bond_info:",
             bond_formats[ out_control->bond_info ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, STR_LINE, "angle_info:",
             angle_formats[ out_control->angle_info ] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* analysis */
    //sprintf( out_control->line, STR_LINE, "molecular_analysis:",
    //     (control->molec_anal ? "yes" : "no") );
    //strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, INT_LINE, "molecular_analysis_frequency:",
             control->molecular_analysis );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );
  }

  /* dump out the buffer */
  if( system->my_rank == MASTER_NODE )
    fprintf( out_control->strj, "%s", out_control->buffer );

  return SUCCESS;
}


int Write_Init_Desc( reax_system *system, control_params *control,
                     output_controls *out_control, mpi_datatypes *mpi_data )
{
  int i, me, np, cnt, buffer_len, buffer_req;
  reax_atom *p_atom;
  MPI_Status status;

  me = system->my_rank;
  np = system->wsize;

  /* skip info */
  Write_Skip_Line( out_control, mpi_data, me,
                   system->bigN * INIT_DESC_LEN, system->bigN );

  if( out_control->traj_method == REG_TRAJ && me == MASTER_NODE )
    buffer_req = system->bigN * INIT_DESC_LEN + 1;
  else buffer_req = system->n * INIT_DESC_LEN + 1;

  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  out_control->line[0] = 0;
  out_control->buffer[0] = 0;
  for( i = 0; i < system->n; ++i ) {
    p_atom = &( system->my_atoms[i] );
    sprintf( out_control->line, INIT_DESC,
             p_atom->orig_id, p_atom->type, p_atom->name,
             system->reax_param.sbp[ p_atom->type ].mass );
    strncpy( out_control->buffer + i*INIT_DESC_LEN,
             out_control->line, INIT_DESC_LEN+1 );
  }

  if( me != MASTER_NODE )
    MPI_Send( out_control->buffer, buffer_req-1, MPI_CHAR, MASTER_NODE,
              np * INIT_DESCS + me, mpi_data->world );
  else{
    buffer_len = system->n * INIT_DESC_LEN;
    for( i = 0; i < np; ++i )
      if( i != MASTER_NODE ) {
        MPI_Recv( out_control->buffer + buffer_len, buffer_req - buffer_len,
                  MPI_CHAR, i, np*INIT_DESCS+i, mpi_data->world, &status );
        MPI_Get_count( &status, MPI_CHAR, &cnt );
        buffer_len += cnt;
      }
    out_control->buffer[buffer_len] = 0;
    fprintf( out_control->strj, "%s", out_control->buffer );
  }

  return SUCCESS;
}


int Init_Traj( reax_system *system, control_params *control,
               output_controls *out_control, mpi_datatypes *mpi_data,
               char *msg )
{
  char fname[MAX_STR];
  int  atom_line_len[ NR_OPT_ATOM ] = { 0, 0, 0, 0,
                                        ATOM_BASIC_LEN, ATOM_wV_LEN,
                                        ATOM_wF_LEN, ATOM_FULL_LEN };
  int  bond_line_len[ NR_OPT_BOND ] = { 0, BOND_BASIC_LEN, BOND_FULL_LEN };
  int  angle_line_len[ NR_OPT_ANGLE ] = { 0, ANGLE_BASIC_LEN };

  /* generate trajectory name */
  sprintf( fname, "%s.trj", control->sim_name );

  /* how should I write atoms? */
  out_control->atom_line_len = atom_line_len[ out_control->atom_info ];
  out_control->write_atoms = ( out_control->atom_line_len ? 1 : 0 );
  /* bonds? */
  out_control->bond_line_len = bond_line_len[ out_control->bond_info ];
  out_control->write_bonds = ( out_control->bond_line_len ? 1 : 0 );
  /* angles? */
  out_control->angle_line_len = angle_line_len[ out_control->angle_info ];
  out_control->write_angles = ( out_control->angle_line_len ? 1 : 0 );

  /* allocate line & buffer space */
  out_control->line = (char*) calloc( MAX_TRJ_LINE_LEN + 1, sizeof(char) );
  out_control->buffer_len = 0;
  out_control->buffer = NULL;

  /* write trajectory header and atom info, if applicable */
  if( out_control->traj_method == REG_TRAJ) {
    if( system->my_rank == MASTER_NODE )
      out_control->strj = fopen( fname, "w" );
  }
  else {
    strcpy( msg, "init_traj: unknown trajectory option" );
    return FAILURE;
  }
  Write_Header( system, control, out_control, mpi_data );
  Write_Init_Desc( system, control, out_control, mpi_data );

  return SUCCESS;
}


int Write_Frame_Header( reax_system *system, control_params *control,
                        simulation_data *data, output_controls *out_control,
                        mpi_datatypes *mpi_data )
{
  int me, num_frm_hdr_lines, my_frm_hdr_lines, buffer_req;

  me = system->my_rank;
  /* frame header lengths */
  num_frm_hdr_lines = 22;
  my_frm_hdr_lines = num_frm_hdr_lines * ( me == MASTER_NODE );
  buffer_req = my_frm_hdr_lines * HEADER_LINE_LEN;
  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  /* only the master node writes into trajectory header */
  if( me == MASTER_NODE ) {
    /* clear the contents of line & buffer */
    out_control->line[0] = 0;
    out_control->buffer[0] = 0;

    /* skip info */
    sprintf( out_control->line, INT_LINE, "chars_to_skip_frame_header:",
             (num_frm_hdr_lines - 1) * HEADER_LINE_LEN );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    /* step & time */
    sprintf( out_control->line, INT_LINE, "step:", data->step );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "time_in_ps:",
             data->step * control->dt );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );


    /* box info */
    sprintf( out_control->line, REAL_LINE, "volume:", system->big_box.V );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL3_LINE, "box_dimensions:",
             system->big_box.box_norms[0],
             system->big_box.box_norms[1],
             system->big_box.box_norms[2] );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL3_LINE,
             "coordinate_angles:", 90.0, 90.0, 90.0 );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );


    /* system T and P */
    sprintf( out_control->line, REAL_LINE, "temperature:", data->therm.T );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "pressure:",
             (control->ensemble==iNPT) ?
             data->iso_bar.P : data->flex_bar.P_scalar );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );


    /* energies */
    sprintf( out_control->line, REAL_LINE, "total_energy:",
             data->sys_en.e_tot );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "total_kinetic:",
             data->sys_en.e_kin );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "total_potential:",
             data->sys_en.e_pot );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "bond_energy:",
             data->sys_en.e_bond );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "atom_energy:",
             data->sys_en.e_ov + data->sys_en.e_un  );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "lone_pair_energy:",
             data->sys_en.e_lp  );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "valence_angle_energy:",
             data->sys_en.e_ang + data->sys_en.e_pen );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "3-body_conjugation:",
             data->sys_en.e_coa );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "hydrogen_bond_energy:",
             data->sys_en.e_hb );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "torsion_angle_energy:",
             data->sys_en.e_tor );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "4-body_conjugation:",
             data->sys_en.e_con );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "vdWaals_energy:",
             data->sys_en.e_vdW );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "electrostatics_energy:",
             data->sys_en.e_ele );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );

    sprintf( out_control->line, REAL_LINE, "polarization_energy:",
             data->sys_en.e_pol );
    strncat( out_control->buffer, out_control->line, HEADER_LINE_LEN+1 );
  }

  /* dump out the buffer */
  if( system->my_rank == MASTER_NODE )
    fprintf( out_control->strj, "%s", out_control->buffer );

  return SUCCESS;
}



int Write_Atoms( reax_system *system, control_params *control,
                 output_controls *out_control, mpi_datatypes *mpi_data )
{
  int i, me, np, line_len, buffer_len, buffer_req, cnt;
  MPI_Status  status;
  reax_atom  *p_atom;

  me = system->my_rank;
  np = system->wsize;
  line_len = out_control->atom_line_len;

  Write_Skip_Line( out_control, mpi_data, me,
                   system->bigN*line_len, system->bigN );

  if( out_control->traj_method == REG_TRAJ && me == MASTER_NODE )
    buffer_req = system->bigN * line_len + 1;
  else buffer_req = system->n * line_len + 1;

  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  /* fill in buffer */
  out_control->line[0] = 0;
  out_control->buffer[0] = 0;
  for( i = 0; i < system->n; ++i ) {
    p_atom = &( system->my_atoms[i] );

    switch( out_control->atom_info ) {
    case OPT_ATOM_BASIC:
      sprintf( out_control->line, ATOM_BASIC,
               p_atom->orig_id, p_atom->x[0], p_atom->x[1], p_atom->x[2],
               p_atom->q );
      break;
    case OPT_ATOM_wF:
      sprintf( out_control->line, ATOM_wF,
               p_atom->orig_id, p_atom->x[0], p_atom->x[1], p_atom->x[2],
               p_atom->f[0], p_atom->f[1], p_atom->f[2], p_atom->q );
      break;
    case OPT_ATOM_wV:
      sprintf( out_control->line, ATOM_wV,
               p_atom->orig_id, p_atom->x[0], p_atom->x[1], p_atom->x[2],
               p_atom->v[0], p_atom->v[1], p_atom->v[2], p_atom->q );
      break;
    case OPT_ATOM_FULL:
      sprintf( out_control->line, ATOM_FULL,
               p_atom->orig_id, p_atom->x[0], p_atom->x[1], p_atom->x[2],
               p_atom->v[0], p_atom->v[1], p_atom->v[2],
               p_atom->f[0], p_atom->f[1], p_atom->f[2], p_atom->q );
      break;
    default:
      fprintf( stderr,
               "write_traj_atoms: unknown atom trajectroy format!\n");
      MPI_Abort( mpi_data->world, UNKNOWN_OPTION );
    }

    strncpy( out_control->buffer + i*line_len, out_control->line, line_len+1 );
  }

  if( me != MASTER_NODE )
    MPI_Send( out_control->buffer, buffer_req-1, MPI_CHAR, MASTER_NODE,
              np*ATOM_LINES+me, mpi_data->world );
  else{
    buffer_len = system->n * line_len;
    for( i = 0; i < np; ++i )
      if( i != MASTER_NODE ) {
        MPI_Recv( out_control->buffer + buffer_len, buffer_req - buffer_len,
                  MPI_CHAR, i, np*ATOM_LINES+i, mpi_data->world, &status );
        MPI_Get_count( &status, MPI_CHAR, &cnt );
        buffer_len += cnt;
      }
    out_control->buffer[buffer_len] = 0;
    fprintf( out_control->strj, "%s", out_control->buffer );
  }

  return SUCCESS;
}


int Write_Bonds(reax_system *system, control_params *control, reax_list *bonds,
                output_controls *out_control, mpi_datatypes *mpi_data)
{
  int i, j, pj, me, np;
  int my_bonds, num_bonds;
  int line_len, buffer_len, buffer_req, cnt;
  MPI_Status  status;
  bond_data  *bo_ij;

  me = system->my_rank;
  np = system->wsize;
  line_len = out_control->bond_line_len;

  /* count the number of bonds I will write */
  my_bonds = 0;
  for( i=0; i < system->n; ++i )
    for( pj = Start_Index(i, bonds); pj < End_Index(i, bonds); ++pj ) {
      j = bonds->select.bond_list[pj].nbr;
      if( system->my_atoms[i].orig_id <= system->my_atoms[j].orig_id &&
          bonds->select.bond_list[pj].bo_data.BO >= control->bg_cut )
        ++my_bonds;
    }

  /* allreduce - total number of bonds */
  MPI_Allreduce( &my_bonds, &num_bonds, 1, MPI_INT, MPI_SUM, mpi_data->world );

  Write_Skip_Line( out_control, mpi_data, me, num_bonds*line_len, num_bonds );

  if( out_control->traj_method == REG_TRAJ && me == MASTER_NODE )
    buffer_req = num_bonds * line_len + 1;
  else buffer_req = my_bonds * line_len + 1;

  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  /* fill in the buffer */
  out_control->line[0] = 0;
  out_control->buffer[0] = 0;

  my_bonds = 0;
  for( i=0; i < system->n; ++i ) {
    for( pj = Start_Index(i, bonds); pj < End_Index(i, bonds); ++pj ) {
      bo_ij = &( bonds->select.bond_list[pj] );
      j = bo_ij->nbr;

      if( system->my_atoms[i].orig_id <= system->my_atoms[j].orig_id &&
          bo_ij->bo_data.BO >= control->bg_cut ) {
        switch( out_control->bond_info ) {
        case OPT_BOND_BASIC:
          sprintf( out_control->line, BOND_BASIC,
                   system->my_atoms[i].orig_id, system->my_atoms[j].orig_id,
                   bo_ij->d, bo_ij->bo_data.BO );
          break;
        case OPT_BOND_FULL:
          sprintf( out_control->line, BOND_FULL,
                   system->my_atoms[i].orig_id, system->my_atoms[j].orig_id,
                   bo_ij->d, bo_ij->bo_data.BO, bo_ij->bo_data.BO_s,
                   bo_ij->bo_data.BO_pi, bo_ij->bo_data.BO_pi2 );
          break;
        default:
          fprintf(stderr, "write_traj_bonds: FATAL! invalid bond_info option");
          MPI_Abort( mpi_data->world, UNKNOWN_OPTION );
        }
        strncpy( out_control->buffer + my_bonds*line_len,
                 out_control->line, line_len+1 );
        ++my_bonds;
      }
    }
  }

  if( me != MASTER_NODE )
    MPI_Send( out_control->buffer, buffer_req-1, MPI_CHAR, MASTER_NODE,
              np*BOND_LINES+me, mpi_data->world );
  else{
    buffer_len = my_bonds * line_len;
    for( i = 0; i < np; ++i )
      if( i != MASTER_NODE ) {
        MPI_Recv( out_control->buffer + buffer_len, buffer_req - buffer_len,
                  MPI_CHAR, i, np*BOND_LINES+i, mpi_data->world, &status );
        MPI_Get_count( &status, MPI_CHAR, &cnt );
        buffer_len += cnt;
      }
    out_control->buffer[buffer_len] = 0;
    fprintf( out_control->strj, "%s", out_control->buffer );
  }

  return SUCCESS;
}


int Write_Angles( reax_system *system, control_params *control,
                  reax_list *bonds, reax_list *thb_intrs,
                  output_controls *out_control, mpi_datatypes *mpi_data )
{
  int i, j, k, pi, pk, me, np;
  int my_angles, num_angles;
  int line_len, buffer_len, buffer_req, cnt;
  bond_data  *bo_ij, *bo_jk;
  three_body_interaction_data *angle_ijk;
  MPI_Status  status;

  me = system->my_rank;
  np = system->wsize;
  line_len = out_control->angle_line_len;

  /* count the number of valence angles I will output */
  my_angles = 0;
  for( j = 0; j < system->n; ++j )
    for( pi = Start_Index(j, bonds); pi < End_Index(j, bonds); ++pi ) {
      bo_ij = &(bonds->select.bond_list[pi]);
      i     = bo_ij->nbr;

      if( bo_ij->bo_data.BO >= control->bg_cut ) // physical j&i bond
        for( pk = Start_Index( pi, thb_intrs );
             pk < End_Index( pi, thb_intrs ); ++pk ) {
          angle_ijk = &(thb_intrs->select.three_body_list[pk]);
          k       = angle_ijk->thb;
          bo_jk   = &(bonds->select.bond_list[ angle_ijk->pthb ]);

          if( system->my_atoms[i].orig_id < system->my_atoms[k].orig_id &&
              bo_jk->bo_data.BO >= control->bg_cut ) // physical j&k bond
            ++my_angles;
        }
    }
  /* total number of valences */
  MPI_Allreduce(&my_angles, &num_angles, 1, MPI_INT, MPI_SUM,  mpi_data->world);

  Write_Skip_Line( out_control, mpi_data, me, num_angles*line_len, num_angles );

  if( out_control->traj_method == REG_TRAJ && me == MASTER_NODE )
    buffer_req = num_angles * line_len + 1;
  else buffer_req = my_angles * line_len + 1;

  if( buffer_req > out_control->buffer_len * DANGER_ZONE )
    Reallocate_Output_Buffer( out_control, buffer_req, mpi_data->world );

  /* fill in the buffer */
  my_angles = 0;
  out_control->line[0] = 0;
  out_control->buffer[0] = 0;
  for( j = 0; j < system->n; ++j )
    for( pi = Start_Index(j, bonds); pi < End_Index(j, bonds); ++pi ) {
      bo_ij = &(bonds->select.bond_list[pi]);
      i     = bo_ij->nbr;

      if( bo_ij->bo_data.BO >= control->bg_cut ) // physical j&i bond
        for( pk = Start_Index( pi, thb_intrs );
             pk < End_Index( pi, thb_intrs ); ++pk ) {
          angle_ijk = &(thb_intrs->select.three_body_list[pk]);
          k       = angle_ijk->thb;
          bo_jk   = &(bonds->select.bond_list[ angle_ijk->pthb ]);

          if( system->my_atoms[i].orig_id < system->my_atoms[k].orig_id &&
              bo_jk->bo_data.BO >= control->bg_cut ) { // physical j&k bond
            sprintf( out_control->line, ANGLE_BASIC,
                     system->my_atoms[i].orig_id, system->my_atoms[j].orig_id,
                     system->my_atoms[k].orig_id, RAD2DEG( angle_ijk->theta ) );

            strncpy( out_control->buffer + my_angles*line_len,
                     out_control->line, line_len+1 );
            ++my_angles;
          }
        }
    }

  if( me != MASTER_NODE )
    MPI_Send( out_control->buffer, buffer_req-1, MPI_CHAR, MASTER_NODE,
              np*ANGLE_LINES+me, mpi_data->world );
  else{
    buffer_len = my_angles * line_len;
    for( i = 0; i < np; ++i )
      if( i != MASTER_NODE ) {
        MPI_Recv( out_control->buffer + buffer_len, buffer_req - buffer_len,
                  MPI_CHAR, i, np*ANGLE_LINES+i, mpi_data->world, &status );
        MPI_Get_count( &status, MPI_CHAR, &cnt );
        buffer_len += cnt;
      }
    out_control->buffer[buffer_len] = 0;
    fprintf( out_control->strj, "%s", out_control->buffer );
  }

  return SUCCESS;
}


int Append_Frame( reax_system *system, control_params *control,
                  simulation_data *data, reax_list **lists,
                  output_controls *out_control, mpi_datatypes *mpi_data )
{
  Write_Frame_Header( system, control, data, out_control, mpi_data );

  if( out_control->write_atoms )
    Write_Atoms( system, control, out_control, mpi_data );

  if( out_control->write_bonds )
    Write_Bonds( system, control, (*lists + BONDS), out_control, mpi_data );

  if( out_control->write_angles )
    Write_Angles( system, control, (*lists + BONDS), (*lists + THREE_BODIES),
                  out_control, mpi_data );

  return SUCCESS;
}


int End_Traj( int my_rank, output_controls *out_control )
{
  if( my_rank == MASTER_NODE )
    fclose( out_control->strj );

  free( out_control->buffer );
  free( out_control->line );

  return SUCCESS;
}
