/*
 *
 *                This source code is part of
 *
 *                 G   R   O   M   A   C   S
 *
 *          GROningen MAchine for Chemical Simulations
 *
 *                        VERSION 3.3.2
 * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
 * Copyright (c) 2001-2007, The GROMACS development team,
 * check out http://www.gromacs.org for more information.

 * 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.
 *
 * If you want to redistribute modifications, please consider that
 * scientific software is very special. Version control is crucial -
 * bugs must be traceable. We will be happy to consider code for
 * inclusion in the official distribution, but derived work must not
 * be called official GROMACS. Details are found in the README & COPYING
 * files - if they are missing, get the official version at www.gromacs.org.
 *
 * To help us fund GROMACS development, we humbly ask that you cite
 * the papers on the package - you can find them in the top README file.
 *
 * For more info, check our website at http://www.gromacs.org
 *
 * And Hey:
 * Groningen Machine for Chemical Simulation
 *
 * ------------------------------------------------------
 * Modified by Rajendra Kumar for g_mmpbsa
 * ------------------------------------------------------
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <stdarg.h>
/* Modified DvdS */
#include "gromacs/pbc.h"
#include "gromacs/macros.h"
#include "gromacs/vec.h"
#include "gromacs/smalloc.h"
#include "g_mmpbsa.h"

#define TEST_NSC 0

#define TEST_ARC 0
#define TEST_DOD 0
#define TEST_CUBE 0

#define UNSP_ICO_DOD      9
#define UNSP_ICO_ARC     10

real   *xpunsp=NULL;
real   del_cube;
int    *ico_wk=NULL, *ico_pt=NULL;
int    n_dot, ico_cube, last_n_dot=0, last_densit=0, last_unsp=0;
int    last_cubus=0;

#define FOURPI (4.*M_PI)
#define TORAD(A)     ((A)*0.017453293)
#define DP_TOL     0.001

#define UPDATE_FL  __file__=__FILE__,__line__=__LINE__
const char * __file__;   /* declared versions of macros */
int  __line__;           /* __FILE__  and __LINE__ */

#ifdef ERROR
#undef ERROR
#endif
#define ERROR UPDATE_FL,error
void error(const char *fmt, ...) {
  va_list args;
  fprintf(stderr,
	  "\n---> ERROR when executing line %i in file %s !\n",
	  __line__,__file__);
  va_start(args,fmt);
  vfprintf(stderr, fmt, args);
  va_end(args);
  fprintf(stderr, "\n---> Execution stopped !\n\n");
}

#define WARNING UPDATE_FL,warning2
void warning2(const char *fmt, ...) {
  va_list args;
  fprintf(stderr,
	  "\n---> WARNING : line %i in file %s\n",
	  __line__,__file__);
  va_start(args,fmt);
  vfprintf(stderr, fmt, args);
  va_end(args);
  fprintf(stderr, " ...!\n\n");
  fflush(stderr);
  fflush(stdout);
}

#define ASIN safe_asin
real safe_asin(real f) {
  if ( (fabs(f) < 1.00) ) return( asin(f) );
  if ( (fabs(f) - 1.00)  <= DP_TOL )
    ERROR("ASIN : invalid argument %f", f);
  return(M_PI_2);
}




/* routines for dot distributions on the surface of the unit sphere */
real rg, rh;

void icosaeder_vertices(real *xus) {
  rh = sqrt(1.-2.*cos(TORAD(72.)))/(1.-cos(TORAD(72.)));
  rg = cos(TORAD(72.))/(1.-cos(TORAD(72.)));
  /* icosaeder vertices */
  xus[ 0] = 0.;                  xus[ 1] = 0.;                  xus[ 2] = 1.;
  xus[ 3] = rh*cos(TORAD(72.));  xus[ 4] = rh*sin(TORAD(72.));  xus[ 5] = rg;
  xus[ 6] = rh*cos(TORAD(144.)); xus[ 7] = rh*sin(TORAD(144.)); xus[ 8] = rg;
  xus[ 9] = rh*cos(TORAD(216.)); xus[10] = rh*sin(TORAD(216.)); xus[11] = rg;
  xus[12] = rh*cos(TORAD(288.)); xus[13] = rh*sin(TORAD(288.)); xus[14] = rg;
  xus[15] = rh;                  xus[16] = 0;                   xus[17] = rg;
  xus[18] = rh*cos(TORAD(36.));  xus[19] = rh*sin(TORAD(36.));  xus[20] = -rg;
  xus[21] = rh*cos(TORAD(108.)); xus[22] = rh*sin(TORAD(108.)); xus[23] = -rg;
  xus[24] = -rh;                 xus[25] = 0;                   xus[26] = -rg;
  xus[27] = rh*cos(TORAD(252.)); xus[28] = rh*sin(TORAD(252.)); xus[29] = -rg;
  xus[30] = rh*cos(TORAD(324.)); xus[31] = rh*sin(TORAD(324.)); xus[32] = -rg;
  xus[33] = 0.;                  xus[34] = 0.;                  xus[35] = -1.;
}


void divarc(real x1, real y1, real z1,
            real x2, real y2, real z2,
            int div1, int div2, real *xr, real *yr, real *zr) {

  real xd, yd, zd, dd, d1, d2, s, x, y, z;
  real phi, sphi, cphi;

  xd = y1*z2-y2*z1;
  yd = z1*x2-z2*x1;
  zd = x1*y2-x2*y1;
  dd = sqrt(xd*xd+yd*yd+zd*zd);
  if (dd < DP_TOL) ERROR("divarc: rotation axis of length %f", dd);

  d1 = x1*x1+y1*y1+z1*z1;
  if (d1 < 0.5) ERROR("divarc: vector 1 of sq.length %f", d1);
  d2 = x2*x2+y2*y2+z2*z2;
  if (d2 < 0.5) ERROR("divarc: vector 2 of sq.length %f", d2);

  phi = ASIN(dd/sqrt(d1*d2));
  phi = phi*((real)div1)/((real)div2);
  sphi = sin(phi); cphi = cos(phi);
  s  = (x1*xd+y1*yd+z1*zd)/dd;

  x = xd*s*(1.-cphi)/dd + x1 * cphi + (yd*z1-y1*zd)*sphi/dd;
  y = yd*s*(1.-cphi)/dd + y1 * cphi + (zd*x1-z1*xd)*sphi/dd;
  z = zd*s*(1.-cphi)/dd + z1 * cphi + (xd*y1-x1*yd)*sphi/dd;
  dd = sqrt(x*x+y*y+z*z);
  *xr = x/dd; *yr = y/dd; *zr = z/dd;
}

int ico_dot_arc(int densit) { /* densit...required dots per unit sphere */
  /* dot distribution on a unit sphere based on an icosaeder *
   * great circle average refining of icosahedral face       */

  int i, j, k, tl, tl2, tn, tess;
  real a, d, x, y, z, x2, y2, z2, x3, y3, z3;
  real xij, yij, zij, xji, yji, zji, xik, yik, zik, xki, yki, zki,
    xjk, yjk, zjk, xkj, ykj, zkj;
  real *xus=NULL;

  /* calculate tessalation level */
  a = sqrt((((real) densit)-2.)/10.);
  tess = (int) ceil(a);
  n_dot = 10*tess*tess+2;
  if (n_dot < densit) {
    ERROR("ico_dot_arc: error in formula for tessalation level (%d->%d, %d)",
	  tess, n_dot, densit);
  }

  snew(xus,3*n_dot);
  xpunsp = xus;
  icosaeder_vertices(xus);

  if (tess > 1) {
    tn = 12;
    a = rh*rh*2.*(1.-cos(TORAD(72.)));
    /* calculate tessalation of icosaeder edges */
    for (i=0; i<11; i++) {
      for (j=i+1; j<12; j++) {
        x = xus[3*i]-xus[3*j];
        y = xus[1+3*i]-xus[1+3*j]; z = xus[2+3*i]-xus[2+3*j];
        d = x*x+y*y+z*z;
        if (fabs(a-d) > DP_TOL) continue;
        for (tl=1; tl<tess; tl++) {
          if (tn >= n_dot) { ERROR("ico_dot: tn exceeds dimension of xus"); }
          divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                 xus[3*j], xus[1+3*j], xus[2+3*j],
		 tl, tess, &xus[3*tn], &xus[1+3*tn], &xus[2+3*tn]);
          tn++;
	}
      }
    }
    /* calculate tessalation of icosaeder faces */
    for (i=0; i<10; i++) {
      for (j=i+1; j<11; j++) {
        x = xus[3*i]-xus[3*j];
        y = xus[1+3*i]-xus[1+3*j]; z = xus[2+3*i]-xus[2+3*j];
        d = x*x+y*y+z*z;
        if (fabs(a-d) > DP_TOL) continue;

        for (k=j+1; k<12; k++) {
          x = xus[3*i]-xus[3*k];
          y = xus[1+3*i]-xus[1+3*k]; z = xus[2+3*i]-xus[2+3*k];
          d = x*x+y*y+z*z;
          if (fabs(a-d) > DP_TOL) continue;
          x = xus[3*j]-xus[3*k];
          y = xus[1+3*j]-xus[1+3*k]; z = xus[2+3*j]-xus[2+3*k];
          d = x*x+y*y+z*z;
          if (fabs(a-d) > DP_TOL) continue;
          for (tl=1; tl<tess-1; tl++) {
            divarc(xus[3*j], xus[1+3*j], xus[2+3*j],
                   xus[3*i], xus[1+3*i], xus[2+3*i],
		   tl, tess, &xji, &yji, &zji);
            divarc(xus[3*k], xus[1+3*k], xus[2+3*k],
                   xus[3*i], xus[1+3*i], xus[2+3*i],
		   tl, tess, &xki, &yki, &zki);

            for (tl2=1; tl2<tess-tl; tl2++) {
              divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                     xus[3*j], xus[1+3*j], xus[2+3*j],
		     tl2, tess, &xij, &yij, &zij);
              divarc(xus[3*k], xus[1+3*k], xus[2+3*k],
                     xus[3*j], xus[1+3*j], xus[2+3*j],
		     tl2, tess, &xkj, &ykj, &zkj);
              divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                     xus[3*k], xus[1+3*k], xus[2+3*k],
		     tess-tl-tl2, tess, &xik, &yik, &zik);
              divarc(xus[3*j], xus[1+3*j], xus[2+3*j],
                     xus[3*k], xus[1+3*k], xus[2+3*k],
		     tess-tl-tl2, tess, &xjk, &yjk, &zjk);
              if (tn >= n_dot) ERROR("ico_dot: tn exceeds dimension of xus");
              divarc(xki, yki, zki, xji, yji, zji, tl2, tess-tl,
		     &x, &y, &z);
              divarc(xkj, ykj, zkj, xij, yij, zij, tl, tess-tl2,
		     &x2, &y2, &z2);
              divarc(xjk, yjk, zjk, xik, yik, zik, tl, tl+tl2,
		     &x3, &y3, &z3);
              x = x+x2+x3; y = y+y2+y3; z = z+z2+z3;
              d = sqrt(x*x+y*y+z*z);
              xus[3*tn] = x/d;
              xus[1+3*tn] = y/d;
              xus[2+3*tn] = z/d;
              tn++;
	    }		/* cycle tl2 */
	  }		/* cycle tl */
	}		/* cycle k */
      }		/* cycle j */
    }			/* cycle i */
    if (n_dot != tn) {
      ERROR("ico_dot: n_dot(%d) and tn(%d) differ", n_dot, tn);
    }
  }		/* end of if (tess > 1) */

  return n_dot;
}		/* end of routine ico_dot_arc */

int ico_dot_dod(int densit) { /* densit...required dots per unit sphere */
  /* dot distribution on a unit sphere based on an icosaeder *
   * great circle average refining of icosahedral face       */

  int i, j, k, tl, tl2, tn, tess, j1, j2;
  real a, d, x, y, z, x2, y2, z2, x3, y3, z3, ai_d, adod;
  real xij, yij, zij, xji, yji, zji, xik, yik, zik, xki, yki, zki,
    xjk, yjk, zjk, xkj, ykj, zkj;
  real *xus=NULL;
  /* calculate tesselation level */
  a = sqrt((((real) densit)-2.)/30.);
  tess = max((int) ceil(a), 1);
  n_dot = 30*tess*tess+2;
  if (n_dot < densit) {
    ERROR("ico_dot_dod: error in formula for tessalation level (%d->%d, %d)",
	  tess, n_dot, densit);
  }

  snew(xus,3*n_dot);
  xpunsp = xus;
  icosaeder_vertices(xus);

  tn=12;
  /* square of the edge of an icosaeder */
  a = rh*rh*2.*(1.-cos(TORAD(72.)));
  /* dodecaeder vertices */
  for (i=0; i<10; i++) {
    for (j=i+1; j<11; j++) {
      x = xus[3*i]-xus[3*j];
      y = xus[1+3*i]-xus[1+3*j]; z = xus[2+3*i]-xus[2+3*j];
      d = x*x+y*y+z*z;
      if (fabs(a-d) > DP_TOL) continue;
      for (k=j+1; k<12; k++) {
        x = xus[3*i]-xus[3*k];
        y = xus[1+3*i]-xus[1+3*k]; z = xus[2+3*i]-xus[2+3*k];
        d = x*x+y*y+z*z;
        if (fabs(a-d) > DP_TOL) continue;
        x = xus[3*j]-xus[3*k];
        y = xus[1+3*j]-xus[1+3*k]; z = xus[2+3*j]-xus[2+3*k];
        d = x*x+y*y+z*z;
        if (fabs(a-d) > DP_TOL) continue;
        x = xus[  3*i]+xus[  3*j]+xus[  3*k];
        y = xus[1+3*i]+xus[1+3*j]+xus[1+3*k];
        z = xus[2+3*i]+xus[2+3*j]+xus[2+3*k];
        d = sqrt(x*x+y*y+z*z);
        xus[3*tn]=x/d; xus[1+3*tn]=y/d; xus[2+3*tn]=z/d;
        tn++;
      }
    }
  }

  if (tess > 1) {
    tn = 32;
    /* square of the edge of an dodecaeder */
    adod = 4.*(cos(TORAD(108.))-cos(TORAD(120.)))/(1.-cos(TORAD(120.)));
    /* square of the distance of two adjacent vertices of ico- and dodecaeder */
    ai_d = 2.*(1.-sqrt(1.-a/3.));

    /* calculate tessalation of mixed edges */
    for (i=0; i<31; i++) {
      j1 = 12; j2 = 32; a = ai_d;
      if (i>=12) { j1=i+1; a = adod; }
      for (j=j1; j<j2; j++) {
        x = xus[3*i]-xus[3*j];
        y = xus[1+3*i]-xus[1+3*j]; z = xus[2+3*i]-xus[2+3*j];
        d = x*x+y*y+z*z;
        if (fabs(a-d) > DP_TOL) continue;
        for (tl=1; tl<tess; tl++) {
          if (tn >= n_dot) {
            ERROR("ico_dot: tn exceeds dimension of xus");
	  }
          divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                 xus[3*j], xus[1+3*j], xus[2+3*j],
		 tl, tess, &xus[3*tn], &xus[1+3*tn], &xus[2+3*tn]);
          tn++;
	}
      }
    }
    /* calculate tessalation of pentakisdodecahedron faces */
    for (i=0; i<12; i++) {
      for (j=12; j<31; j++) {
        x = xus[3*i]-xus[3*j];
        y = xus[1+3*i]-xus[1+3*j]; z = xus[2+3*i]-xus[2+3*j];
        d = x*x+y*y+z*z;
        if (fabs(ai_d-d) > DP_TOL) continue;

        for (k=j+1; k<32; k++) {
          x = xus[3*i]-xus[3*k];
          y = xus[1+3*i]-xus[1+3*k]; z = xus[2+3*i]-xus[2+3*k];
          d = x*x+y*y+z*z;
          if (fabs(ai_d-d) > DP_TOL) continue;
          x = xus[3*j]-xus[3*k];
          y = xus[1+3*j]-xus[1+3*k]; z = xus[2+3*j]-xus[2+3*k];
          d = x*x+y*y+z*z;
          if (fabs(adod-d) > DP_TOL) continue;
          for (tl=1; tl<tess-1; tl++) {
            divarc(xus[3*j], xus[1+3*j], xus[2+3*j],
                   xus[3*i], xus[1+3*i], xus[2+3*i],
		   tl, tess, &xji, &yji, &zji);
            divarc(xus[3*k], xus[1+3*k], xus[2+3*k],
                   xus[3*i], xus[1+3*i], xus[2+3*i],
		   tl, tess, &xki, &yki, &zki);

            for (tl2=1; tl2<tess-tl; tl2++) {
              divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                     xus[3*j], xus[1+3*j], xus[2+3*j],
		     tl2, tess, &xij, &yij, &zij);
              divarc(xus[3*k], xus[1+3*k], xus[2+3*k],
                     xus[3*j], xus[1+3*j], xus[2+3*j],
		     tl2, tess, &xkj, &ykj, &zkj);
              divarc(xus[3*i], xus[1+3*i], xus[2+3*i],
                     xus[3*k], xus[1+3*k], xus[2+3*k],
		     tess-tl-tl2, tess, &xik, &yik, &zik);
              divarc(xus[3*j], xus[1+3*j], xus[2+3*j],
                     xus[3*k], xus[1+3*k], xus[2+3*k],
		     tess-tl-tl2, tess, &xjk, &yjk, &zjk);
              if (tn >= n_dot) {
                ERROR("ico_dot: tn exceeds dimension of xus");
	      }
              divarc(xki, yki, zki, xji, yji, zji, tl2, tess-tl,
		     &x, &y, &z);
              divarc(xkj, ykj, zkj, xij, yij, zij, tl, tess-tl2,
		     &x2, &y2, &z2);
              divarc(xjk, yjk, zjk, xik, yik, zik, tl, tl+tl2,
		     &x3, &y3, &z3);
              x = x+x2+x3; y = y+y2+y3; z = z+z2+z3;
              d = sqrt(x*x+y*y+z*z);
              xus[3*tn] = x/d;
              xus[1+3*tn] = y/d;
              xus[2+3*tn] = z/d;
              tn++;
	    }		/* cycle tl2 */
	  }		/* cycle tl */
	}		/* cycle k */
      }		/* cycle j */
    }			/* cycle i */
    if (n_dot != tn) {
      ERROR("ico_dot: n_dot(%d) and tn(%d) differ", n_dot, tn);
    }
  }		/* end of if (tess > 1) */

    return n_dot;
}		/* end of routine ico_dot_dod */

int unsp_type(int densit) {
  int i1, i2;
  i1 = 1;
  while (10*i1*i1+2 < densit) i1++;
  i2 = 1;
  while (30*i2*i2+2 < densit) i2++;
  if (10*i1*i1-2 < 30*i2*i2-2) return UNSP_ICO_ARC;
  else return UNSP_ICO_DOD;
}

int make_unsp(int densit, int mode, int * num_dot, int cubus) {
  int ndot, ico_cube_cb, i, j, k, l, ijk, tn, tl, tl2;
  real *xus;
  int  *work;
  real x, y, z;

  if (xpunsp) free(xpunsp); if (ico_wk) free(ico_wk);

  k=1; if (mode < 0) { k=0; mode = -mode; }
  if (mode == UNSP_ICO_ARC)      { ndot = ico_dot_arc(densit); }
  else if (mode == UNSP_ICO_DOD)      { ndot = ico_dot_dod(densit); }
  else {
    WARNING("make_unsp: mode %c%d not allowed", (k) ? '+':'-',mode);
    return 1;
  }

  last_n_dot = ndot; last_densit = densit; last_unsp = mode;
  *num_dot=ndot; if (k) return 0;

  /* in the following the dots of the unit sphere may be resorted */
  last_unsp = -last_unsp;

  /* determine distribution of points in elementary cubes */
  if (cubus) {
    ico_cube = cubus;
  }
  else {
    last_cubus = 0;
    i=1;
    while (i*i*i*2 < ndot) i++;
    ico_cube = max(i-1, 0);
  }
  ico_cube_cb = ico_cube*ico_cube*ico_cube;
  del_cube=2./((real)ico_cube);
  snew(work,ndot);
  xus = xpunsp;
  for (l=0; l<ndot; l++) {
    i = max((int) floor((1.+xus[3*l])/del_cube), 0);
    if (i>=ico_cube) i = ico_cube-1;
    j = max((int) floor((1.+xus[1+3*l])/del_cube), 0);
    if (j>=ico_cube) j = ico_cube-1;
    k = max((int) floor((1.+xus[2+3*l])/del_cube), 0);
    if (k>=ico_cube) k = ico_cube-1;
    ijk = i+j*ico_cube+k*ico_cube*ico_cube;
    work[l] = ijk;
  }

  snew(ico_wk,2*ico_cube_cb+1);

  ico_pt = ico_wk+ico_cube_cb;
  for (l=0; l<ndot; l++) {
    ico_wk[work[l]]++;   /* dots per elementary cube */
  }

  /* reordering of the coordinate array in accordance with box number */
  tn=0;
  for (i=0; i<ico_cube; i++) {
    for (j=0; j<ico_cube; j++) {
      for (k=0; k<ico_cube; k++) {
        tl=0;
        tl2 = tn;
        ijk = i+ico_cube*j+ico_cube*ico_cube*k;
        *(ico_pt+ijk) = tn;
        for (l=tl2; l<ndot; l++) {
          if (ijk == work[l]) {
            x = xus[3*l]; y = xus[1+3*l]; z = xus[2+3*l];
            xus[3*l] = xus[3*tn];
            xus[1+3*l] = xus[1+3*tn]; xus[2+3*l] = xus[2+3*tn];
            xus[3*tn] = x; xus[1+3*tn] = y; xus[2+3*tn] = z;
            ijk = work[l]; work[l]=work[tn]; work[tn]=ijk;
            tn++; tl++;
	  }
	}
        *(ico_wk+ijk) = tl;
      }		/* cycle k */
    }			/* cycle j */
  }			/* cycle i */
  free(work);

  return 0;
}


typedef struct _stwknb {
  real x;
  real y;
  real z;
  real dot;
} Neighb;

int Mod_nsc_dclm_pbc(rvec *coords, real *radius, int nat,
		 int  densit, int mode,
		 real *value_of_area, double **at_area,
		 real *value_of_vol,
		 double ** at_vol,
		 real **lidots, int *nu_dots,
		 atom_id index[],int ePBC,matrix box)
{
  int iat, i, ii, iii, ix, iy, iz, ixe, ixs, iye, iys, ize, izs, i_ac;
  int jat, j, jj, jjj, jx, jy, jz;
  int distribution;
  int l;
  int maxnei, nnei, last, maxdots=0;
  int *wkdot=NULL, *wkbox=NULL, *wkat1=NULL, *wkatm=NULL;
  Neighb  *wknb, *ctnb;
  int iii1, iii2, iiat, lfnr=0, i_at, j_at;
  real dx, dy, dz, dd, ai, aisq, ajsq, aj, as, a;
  real xi, yi, zi, xs=0., ys=0., zs=0.;
  real dotarea, area, vol=0.;
  real *xus, *dots=NULL;
  double *atom_area=NULL;
  int  nxbox, nybox, nzbox, nxy, nxyz;
  real xmin=0, ymin=0, zmin=0, xmax, ymax, zmax, ra2max, d, *pco;
  /* Added DvdS 2006-07-19 */
  t_pbc pbc;
  rvec  ddx,*x=NULL;
  int   iat_xx,jat_xx;

 ////////ADDED FOR SOLVENT ACCESSIBLE VOLUME OF EACH ATOM/////
  double *atom_vol=NULL;
  if (mode & FLAG_VOLUME)	{
	  if(atom_vol == NULL)
		  snew(atom_vol,nat);
	  else
		  srenew(atom_vol,nat);
  }
////////////////////////////////////////////////////////////////

  distribution = unsp_type(densit);
  if (distribution != -last_unsp || last_cubus != 4 ||
      (densit != last_densit && densit != last_n_dot)) {
    if (make_unsp(densit, (-distribution), &n_dot, 4))
      return 1;
  }
  xus = xpunsp;

  dotarea = FOURPI/(real) n_dot;
  area = 0.;

  if (debug)
    fprintf(debug,"nsc_dclm: n_dot=%5d %9.3f\n", n_dot, dotarea);

  /* start with neighbour list */
  /* calculate neighbour list with the box algorithm */
  if (nat==0) {
    WARNING("nsc_dclm: no surface atoms selected");
    return 1;
  }
  if (mode & FLAG_VOLUME)
    vol=0.;
  if (mode & FLAG_DOTS) {
    maxdots = (3*n_dot*nat)/10;
    /* should be set to NULL on first user call */
      if(dots==NULL)
      {
          snew(dots,maxdots);
      }
      else
      {
          srenew(dots,maxdots);
      }

    lfnr=0;
  }
  if (mode & FLAG_ATOM_AREA)
  {
      /* should be set to NULL on first user call */
      if(atom_area==NULL)
      {
          snew(atom_area,nat);
      }
      else
      {
          srenew(atom_area,nat);
      }
  }

  /* Compute minimum size for grid cells */
  ra2max = radius[index[0]];
  for (iat_xx=1; (iat_xx<nat); iat_xx++) {
    iat = index[iat_xx];
    ra2max = max(ra2max, radius[iat]);
  }
  ra2max = 2*ra2max;

  /* Added DvdS 2006-07-19 */
  /* Updated 2008-10-09 */
  if (box) {
    set_pbc(&pbc,ePBC,box);
    snew(x,nat);
    for(i=0; (i<nat); i++) {
      iat  = index[0];
      copy_rvec(coords[iat],x[i]);
    }
    put_atoms_in_triclinic_unitcell(ecenterTRIC,box,nat,x);
    nxbox = max(1,floor(norm(box[XX])/ra2max));
    nybox = max(1,floor(norm(box[YY])/ra2max));
    nzbox = max(1,floor(norm(box[ZZ])/ra2max));
    if (debug)
      fprintf(debug,"nbox = %d, %d, %d\n",nxbox,nybox,nzbox);
  }
  else {
    /* dimensions of atomic set, cell edge is 2*ra_max */
    iat  = index[0];
    xmin = coords[iat][XX]; xmax = xmin; xs=xmin;
    ymin = coords[iat][YY]; ymax = ymin; ys=ymin;
    zmin = coords[iat][ZZ]; zmax = zmin; zs=zmin;
    ra2max = radius[iat];

    for (iat_xx=1; (iat_xx<nat); iat_xx++) {
      iat = index[iat_xx];
      pco = coords[iat];
      xmin = min(xmin, *pco);     xmax = max(xmax, *pco);
      ymin = min(ymin, *(pco+1)); ymax = max(ymax, *(pco+1));
      zmin = min(zmin, *(pco+2)); zmax = max(zmax, *(pco+2));
      xs= xs+ *pco; ys = ys+ *(pco+1); zs= zs+ *(pco+2);
    }
    xs = xs/ (real) nat;
    ys = ys/ (real) nat;
    zs = zs/ (real) nat;
    if (debug)
      fprintf(debug,"nsc_dclm: n_dot=%5d ra2max=%9.3f %9.3f\n", n_dot, ra2max, dotarea);

    d = xmax-xmin; nxbox = (int) max(ceil(d/ra2max), 1.);
    d = (((real)nxbox)*ra2max-d)/2.;
    xmin = xmin-d; xmax = xmax+d;
    d = ymax-ymin; nybox = (int) max(ceil(d/ra2max), 1.);
    d = (((real)nybox)*ra2max-d)/2.;
    ymin = ymin-d; ymax = ymax+d;
    d = zmax-zmin; nzbox = (int) max(ceil(d/ra2max), 1.);
    d = (((real)nzbox)*ra2max-d)/2.;
    zmin = zmin-d; zmax = zmax+d;
  }
  /* Help variables */
  nxy = nxbox*nybox;
  nxyz = nxy*nzbox;

  /* box number of atoms */
  snew(wkatm,nat);
  snew(wkat1,nat);
  snew(wkdot,n_dot);
  snew(wkbox,nxyz+1);

  if (box) {
    matrix box_1;
    rvec   x_1;
    int    ix,iy,iz,m;
    m_inv(box,box_1);
    for(i=0; (i<nat); i++) {
      mvmul(box_1,x[i],x_1);
      ix = ((int)floor(x_1[XX]*nxbox) + 2*nxbox) % nxbox;
      iy = ((int)floor(x_1[YY]*nybox) + 2*nybox) % nybox;
      iz = ((int)floor(x_1[ZZ]*nzbox) + 2*nzbox) % nzbox;
      j =  ix + iy*nxbox + iz*nxbox*nybox;
      if (debug)
	fprintf(debug,"Atom %d cell index %d. x = (%8.3f,%8.3f,%8.3f) fc = (%8.3f,%8.3f,%8.3f)\n",
		i,j,x[i][XX],x[i][YY],x[i][ZZ],x_1[XX],x_1[YY],x_1[ZZ]);
      range_check(j,0,nxyz);
      wkat1[i] = j;
      wkbox[j]++;
    }
  }
  else {
    /* Put the atoms in their boxes */
    for (iat_xx=0; (iat_xx<nat); iat_xx++) {
      iat = index[iat_xx];
      pco = coords[iat];
      i = (int) max(floor((pco[XX]-xmin)/ra2max), 0);
      i = min(i,nxbox-1);
      j = (int) max(floor((pco[YY]-ymin)/ra2max), 0);
      j = min(j,nybox-1);
      l = (int) max(floor((pco[ZZ]-zmin)/ra2max), 0);
      l = min(l,nzbox-1);
      i = i+j*nxbox+l*nxy;
      wkat1[iat_xx] = i;
      wkbox[i]++;
    }
  }

  /* sorting of atoms in accordance with box numbers */
  j = wkbox[0];
  for (i=1; i<nxyz; i++)
    j= max(wkbox[i], j);
  for (i=1; i<=nxyz; i++)
    wkbox[i] += wkbox[i-1];

  /* maxnei = (int) floor(ra2max*ra2max*ra2max*0.5); */
  maxnei = min(nat, 27*j);
  snew(wknb,maxnei);
  for (iat_xx=0; iat_xx<nat; iat_xx++) {
    iat = index[iat_xx];
    range_check(wkat1[iat_xx],0,nxyz);
    wkatm[--wkbox[wkat1[iat_xx]]] = iat_xx;
    if (debug)
      fprintf(debug,"atom %5d on place %5d\n", iat, wkbox[wkat1[iat_xx]]);
  }

  if (debug) {
    fprintf(debug,"nsc_dclm: n_dot=%5d ra2max=%9.3f %9.3f\n",
	    n_dot, ra2max, dotarea);
    fprintf(debug,"neighbour list calculated/box(xyz):%d %d %d\n",
	    nxbox, nybox, nzbox);

    for (i=0; i<nxyz; i++)
      fprintf(debug,"box %6d : atoms %4d-%4d    %5d\n",
	      i, wkbox[i], wkbox[i+1]-1, wkbox[i+1]-wkbox[i]);
    for (i=0; i<nat; i++) {
      fprintf(debug,"list place %5d by atom %7d\n", i, index[wkatm[i]]);
    }
  }

  /* calculate surface for all atoms, step cube-wise */
  for (iz=0; iz<nzbox; iz++) {
    iii = iz*nxy;
    if (box) {
      izs = iz-1;
      ize = min(iz+2,izs+nzbox);
    }
    else {
      izs = max(iz-1,0);
      ize = min(iz+2, nzbox);
    }
    for (iy=0; iy<nybox; iy++) {
      ii = iy*nxbox+iii;
      if (box) {
	iys = iy-1;
	iye = min(iy+2,iys+nybox);
      }
      else {
	iys = max(iy-1,0);
	iye = min(iy+2, nybox);
      }
      for (ix=0; ix<nxbox; ix++) {
	i = ii+ix;
	iii1=wkbox[i];
	iii2=wkbox[i+1];
	if (iii1 >= iii2)
	  continue;
	if (box) {
	  ixs = ix-1;
	  ixe = min(ix+2,ixs+nxbox);
	}
	else {
	  ixs = max(ix-1,0);
	  ixe = min(ix+2, nxbox);
	}
	iiat = 0;
	/* make intermediate atom list */
	for (jz=izs; jz<ize; jz++) {
	  jjj = ((jz+nzbox) % nzbox)*nxy;
	  for (jy=iys; jy<iye; jy++) {
	    jj = ((jy+nybox) % nybox)*nxbox+jjj;
	    for (jx=ixs; jx<ixe; jx++) {
	      j = jj+((jx+nxbox) % nxbox);
	      for (jat=wkbox[j]; jat<wkbox[j+1]; jat++) {
		range_check(wkatm[jat],0,nat);
		range_check(iiat,0,nat);
		wkat1[iiat] = wkatm[jat];
		iiat++;
	      }     /* end of cycle "jat" */
	    }       /* end of cycle "jx" */
	  }       /* end of cycle "jy" */
	}       /* end of cycle "jz" */
	for (iat=iii1; iat<iii2; iat++) {
	  i_at = index[wkatm[iat]];
	  ai   = radius[i_at];
	  aisq = ai*ai;
	  pco  = coords[i_at];
	  xi = pco[XX]; yi = pco[YY]; zi = pco[ZZ];
	  for (i=0; i<n_dot; i++)
	    wkdot[i] = 0;

	  ctnb = wknb; nnei = 0;
	  for (j=0; j<iiat; j++) {
	    j_at = index[wkat1[j]];
	    if (j_at == i_at)
	      continue;

	    aj   = radius[j_at];
	    ajsq = aj*aj;
	    pco  = coords[j_at];

	    /* Added DvdS 2006-07-19 */
	    if (box) {
	      /*rvec xxi;

	      xxi[XX] = xi;
	      xxi[YY] = yi;
	      xxi[ZZ] = zi;
	      pbc_dx(&pbc,pco,xxi,ddx);*/
	      pbc_dx(&pbc,coords[j_at],coords[i_at],ddx);
	      dx = ddx[XX];
	      dy = ddx[YY];
	      dz = ddx[ZZ];
	    }
	    else {
	      dx = pco[XX]-xi;
	      dy = pco[YY]-yi;
	      dz = pco[ZZ]-zi;
	    }
	    dd = dx*dx+dy*dy+dz*dz;
	    as = ai+aj;
	    if (dd > as*as) {
	      continue;
	    }
	    nnei++;
	    ctnb->x = dx;
	    ctnb->y = dy;
	    ctnb->z = dz;
	    ctnb->dot = (dd+aisq-ajsq)/(2.*ai); /* reference dot product */
	    ctnb++;
	  }

	  /* check points on accessibility */
	  if (nnei) {
	    last = 0; i_ac = 0;
	    for (l=0; l<n_dot; l++) {
	      if (xus[3*l]*(wknb+last)->x+
		  xus[1+3*l]*(wknb+last)->y+
		  xus[2+3*l]*(wknb+last)->z <= (wknb+last)->dot) {
		for (j=0; j<nnei; j++) {
		  if (xus[3*l]*(wknb+j)->x+xus[1+3*l]*(wknb+j)->y+
		      xus[2+3*l]*(wknb+j)->z > (wknb+j)->dot) {
		    last = j;
		    break;
		  }
		}
		if (j >= nnei) {
		  i_ac++;
		  wkdot[l] = 1;
		}
	      }     /* end of cycle j */
	    }       /* end of cycle l */
	  }
	  else {
	    i_ac  = n_dot;
	    for (l=0; l < n_dot; l++)
	      wkdot[l] = 1;
	  }

	  if (debug)
	    fprintf(debug,"i_ac=%d, dotarea=%8.3f, aisq=%8.3f\n",
		    i_ac, dotarea, aisq);

	  a = aisq*dotarea* (real) i_ac;
	  area = area + a;
	  if (mode & FLAG_ATOM_AREA) {
	    range_check(wkatm[iat],0,nat);
	    atom_area[wkatm[iat]] = a;
	  }
	  if (mode & FLAG_DOTS) {
	    for (l=0; l<n_dot; l++) {
	      if (wkdot[l]) {
		lfnr++;
		if (maxdots <= 3*lfnr+1) {
            maxdots = maxdots+n_dot*3;
            srenew(dots,maxdots);
		}
		dots[3*lfnr-3] = ai*xus[3*l]+xi;
		dots[3*lfnr-2] = ai*xus[1+3*l]+yi;
		dots[3*lfnr-1] = ai*xus[2+3*l]+zi;
	      }
	    }
	  }
	  if (mode & FLAG_VOLUME) {
	    dx=0.; dy=0.; dz=0.;
	    for (l=0; l<n_dot; l++) {
	      if (wkdot[l]) {
		dx=dx+xus[3*l];
		dy=dy+xus[1+3*l];
		dz=dz+xus[2+3*l];
	      }
	    }

//////////////////////////////////////ADDED FOR SOLVENT ACCESSIBLE VOLUME OF EACH ATOM///////////////////////////////////////
	    if (mode & FLAG_VOLUME)
	    	atom_vol[wkatm[iat]] = (aisq*(dx*(xi-xs)+dy*(yi-ys)+dz*(zi-zs)+ai* (real) i_ac) ) * (FOURPI/(3.* (real) n_dot));
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	    vol = vol+aisq*(dx*(xi-xs)+dy*(yi-ys)+dz*(zi-zs)+ai* (real) i_ac);
	  }

	}         /* end of cycle "iat" */
      }           /* end of cycle "ix" */
    }           /* end of cycle "iy" */
  }           /* end of cycle "iz" */

  sfree(wkatm);
  sfree(wkat1);
  sfree(wkdot);
  sfree(wkbox);
  sfree(wknb);
  if (box)
  {
    sfree(x);
  }
  if (mode & FLAG_VOLUME) {
    vol = vol*FOURPI/(3.* (real) n_dot);
    *value_of_vol = vol;
  }

  if (mode & FLAG_DOTS) {
    *nu_dots = lfnr;
    *lidots = dots;
  }
  if (mode & FLAG_ATOM_AREA) {
	////ADDED FOR SOLVENT ACCESSIBLE VOLUME OF EACH ATOM//////
    if(at_area != NULL)
    	*at_area = atom_area;
  }
  if (mode & FLAG_VOLUME) {
    if(at_vol != NULL)
    	*at_vol = atom_vol;
   /////////////////////////////////////////////////////////
  }


  *value_of_area = area;

  if (debug)
    fprintf(debug,"area=%8.3f\n", area);

  return 0;
}


#if TEST_NSC > 0
#define NAT 2
main () {

  int i, j, ndots;
  real co[3*NAT], ra[NAT], area, volume, a, b, c;
  real * dots;
  real * at_area;
  FILE *fp;


  a = 1.; c= 0.1;
  fp = fopen("nsc.txt", "w+");
  for (i=1; i<=NAT; i++) {
    j = i-1;
    co[3*i-3] = j*1*c;
    co[3*i-2] = j*1*c;
    co[3*i-1] = j*1*c;
    /*
      co[3*i-3] = i*1.4;
      co[3*i-2] = 0.;
      co[3*i-1] = 0.;
    */
    /*
      co[3*i-2] = a*0.3;
      a = -a; b=0;
      if (i%3 == 0) b=0.5;
      co[3*i-1] = b;
      ra[i-1] = 2.0;
    */
    ra[i-1] = (1.+j*0.5)*c;
  }
  /*
    if (NSC(co, ra, NAT, 42, NULL, &area,
  */
  if (NSC(co, ra, NAT, 42, NULL, &area,
	  NULL,NULL,NULL,NULL)) ERROR("error in NSC");
  fprintf(fp, "\n");
  fprintf(fp, "area     : %8.3f\n", area);
  fprintf(fp, "\n");
  fprintf(fp, "\n");
  fprintf(fp, "next call\n");
  fprintf(fp, "\n");
  fprintf(fp, "\n");

  if (NSC(co, ra, NAT, 42,FLAG_VOLUME | FLAG_ATOM_AREA | FLAG_DOTS, &area,
	  &at_area, &volume,
	  &dots, &ndots)) ERROR("error in NSC");

  fprintf(fp, "\n");
  fprintf(fp, "area     : %8.3f\n", area);
  printf("area     : %8.3f\n", area);
  fprintf(fp, "volume   : %8.3f\n", volume);
  printf("volume   : %8.3f\n", volume);
  fprintf(fp, "ndots    : %8d\n", ndots);
  printf("ndots    : %8d\n", ndots);
  fprintf(fp, "\n");
  for (i=1; i<=NAT; i++) {
    fprintf(fp, "%4d ATOM %7.2f %7.2f %7.2f  ra=%4.1f  area=%8.3f\n",
	    i, co[3*i-3], co[3*i-2], co[3*i-1], ra[i-1], at_area[i-1]);
  }
  fprintf(fp, "\n");
  fprintf(fp, "DOTS : %8d\n", ndots);
  for (i=1; i<=ndots; i++) {
    fprintf(fp, "%4d DOTS %8.2f %8.2f %8.2f\n",
	    i, dots[3*i-3], dots[3*i-2], dots[3*i-1]);
  }
}
#endif
