/***************************************************************************
                          forcefuncvdw.c  -  description
                             -------------------
    begin                : Fri Mar 18 12:25:42 2005
    copyright            : (C) 2002 by Cavalli Andrea
    email                : cavalli@bioc.unizh.ch
**************************************************************************/
/***************************************************************************
 *                                                                         *
 *   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.                                   *
 *                                                                         *
 ***************************************************************************/

#define COOR_DIM 4


void force_xxsn_d(const int * first,
		  const int * second,
		  const int * boundarry,
		  const int natoms,
		  const double * coor,
		  double * force,
		  const double  c2,
		  const double c_on2,
		  const int * type_code,
		  const int type_size,
		  const double * vdw_data){
  int f;
  int fpos;
  int s;
  int spos;
  int b1,b2;
  double fracX;
  double fracY;
  double fracZ;
  double dx,dy,dz;
  double ix,iy,iz;
  double jx,jy,jz;
  double tx,ty,tz;
  double d2;
  double d6;
  double d2inv;
  double d6inv;
  double d12inv;
  double frac;
  double nb6;
  double nb12;
  double A,B;
  int tc1,tc2;
  int data_pos;
  const double c2inv = 1.0/c2;
  const double c6inv = c2inv*c2inv*c2inv;
  const double c12inv = c6inv*c6inv;
  const double c18inv = c12inv*c6inv;
  const double one = 1.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    b1 = boundarry[2*i];
    b2 = boundarry[2*i+1];
    fracX = 0;
    fracY = 0;
    fracZ = 0;
    fpos = COOR_DIM*f;
    ix = coor[fpos];
    iy = coor[fpos+1];
    iz = coor[fpos+2];
    tc1 = type_code[f];
    for(j= b1;j<b2;j++){
      s = second[j];
      spos = COOR_DIM*s;
      jx = coor[spos];
      jy = coor[spos+1];
      jz = coor[spos+2];
      dx = ix-jx;
      dy = iy-jy;
      dz = iz-jz;
      d2 = dx*dx+dy*dy+dz*dz;
      if(d2<c2){
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	d2inv = one/d2;
	d6 = d2*d2*d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	nb6 = B*(d6inv-d6*c12inv); //mult by B
	nb12= A*(d12inv-d6*c18inv);
	frac = (nb12-nb6)*d2inv;
	tx = frac*dx;
	ty = frac*dy;
	tz = frac*dz;
	fracX = fracX - tx;
	fracY = fracY - ty;
	fracZ = fracZ - tz;
	force[spos] = force[spos] + tx;
	force[spos+1] = force[spos+1] + ty;
	force[spos+2] = force[spos+2] + tz;
      }
    }
    force[fpos] = force[fpos] + fracX;
    force[fpos+1] = force[fpos+1] + fracY;
    force[fpos+2] = force[fpos+2] + fracZ;
  }
}



void force_xxsn_f(const int * first,
		  const int * second,
		  const int * boundarry,
		  const int natoms,
		  const float * coor,
		  float * force,
		  const float  c2,
		  const float  c2_on,
		  const int * type_code,
		  const int type_size,
		  const float * vdw_data){
  int f;
  int fpos;
  int s;
  int spos;
  int b1,b2;
  float fracX;
  float fracY;
  float fracZ;
  float dx,dy,dz;
  float ix,iy,iz;
  float jx,jy,jz;
  float tx,ty,tz;
  float d2;
  float d6;
  float d2inv;
  float d6inv;
  float d12inv;
  float frac;
  float nb6;
  float nb12;
  float A,B;
  int tc1,tc2;
  int data_pos;
  const float c2inv = 1.0/c2;
  const float c6inv = c2inv*c2inv*c2inv;
  const float c12inv = c6inv*c6inv;
  const float c18inv = c12inv*c6inv;
  const float one = 1.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    b1 = boundarry[2*i];
    b2 = boundarry[2*i+1];
    fracX = 0;
    fracY = 0;
    fracZ = 0;
    fpos = COOR_DIM*f;
    ix = coor[fpos];
    iy = coor[fpos+1];
    iz = coor[fpos+2];
    tc1 = type_code[f];
    for(j= b1;j<b2;j++){
      s = second[j];
      spos = COOR_DIM*s;
      jx = coor[spos];
      jy = coor[spos+1];
      jz = coor[spos+2];
      dx = ix-jx;
      dy = iy-jy;
      dz = iz-jz;
      d2 = dx*dx+dy*dy+dz*dz;
      if(d2<c2){
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	d2inv = one/d2;
	d6 = d2*d2*d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	nb6 = B*(d6inv-d6*c12inv); //mult by B
	nb12= A*(d12inv-d6*c18inv);
	frac = (nb12-nb6)*d2inv;
	tx = frac*dx;
	ty = frac*dy;
	tz = frac*dz;
	fracX = fracX - tx;
	fracY = fracY - ty;
	fracZ = fracZ - tz;
	force[spos] = force[spos] + tx;
	force[spos+1] = force[spos+1] + ty;
	force[spos+2] = force[spos+2] + tz;
      }
    }
    force[fpos] = force[fpos] + fracX;
    force[fpos+1] = force[fpos+1] + fracY;
    force[fpos+2] = force[fpos+2] + fracZ;
  }
}


void force_xxswn_d(const int * first,
		   const int * second,
		   const int * boundarry,
		   const int natoms,
		   const double * coor,
		   double * force,
		   const double  c2,
		   const double  c_on2,
		   const int * type_code,
		   const int type_size,
		   const double * vdw_data){
  int f;
  int fpos;
  int s;
  int spos;
  int b1,b2;
  double fracX;
  double fracY;
  double fracZ;
  double dx,dy,dz;
  double ix,iy,iz;
  double jx,jy,jz;
  double tx,ty,tz;
  double d2;
  double d6;
  double d2inv;
  double d6inv;
  double d12inv;
  double sh1;
  double sh2;
  double sw;
  double sw1;
  double frac;
  double nbvdw;
  double A,B;
  int tc1,tc2;
  int data_pos;
  const double c2diffinv = 1.0/((c2-c_on2)*(c2-c_on2)*(c2-c_on2));
  const double one = 1.0;
  const double two = 2.0;
  const double three = 3.0;
  const double four = 4.0;
  const double six_inv = 1.0/6.0; 
  const double twelve_inv = 1.0/12.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    b1 = boundarry[2*i];
    b2 = boundarry[2*i+1];
    fracX = 0;
    fracY = 0;
    fracZ = 0;
    fpos = COOR_DIM*f;
    ix = coor[fpos];
    iy = coor[fpos+1];
    iz = coor[fpos+2];
    tc1 = type_code[f];
    for(j= b1;j<b2;j++){
      s = second[j];
      spos = COOR_DIM*s;
      jx = coor[spos];
      jy = coor[spos+1];
      jz = coor[spos+2];
      dx = ix-jx;
      dy = iy-jy;
      dz = iz-jz;
      d2 = dx*dx+dy*dy+dz*dz;
      if(d2<c2){
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	d6 = d2*d2*d2;
	nbvdw = A*d12inv - B*d6inv;
	if(d2>c_on2){
	  sh1 = c2-d2;
	  sh2 = (c2+two*d2-three*c_on2);
	  sw = sh1*sh2;
	  sw1= four*(sh1-sh2);
	  frac = nbvdw*sw*d2inv-(twelve_inv*A*d12inv-six_inv*B*d6inv)*sw1;
	  frac = frac*c2diffinv*sh1;
	}
	else frac = nbvdw*d2inv;
	tx = frac*dx;
	ty = frac*dy;
	tz = frac*dz;
	fracX = fracX - tx;
	fracY = fracY - ty;
	fracZ = fracZ - tz;
	force[spos] = force[spos] + tx;
	force[spos+1] = force[spos+1] + ty;
	force[spos+2] = force[spos+2] + tz;
      }
    }
    force[fpos] = force[fpos] + fracX;
    force[fpos+1] = force[fpos+1] + fracY;
    force[fpos+2] = force[fpos+2] + fracZ;
  }
}

void force_xxswn_f(const int * first,
		   const int * second,
		   const int * boundarry,
		   const int natoms,
		   const float * coor,
		   float * force,
		   const float  c2,
		   const float  c_on2,
		   const int * type_code,
		   const int type_size,
		   const float * vdw_data){
  int f;
  int fpos;
  int s;
  int spos;
  int b1,b2;
  float fracX;
  float fracY;
  float fracZ;
  float dx,dy,dz;
  float ix,iy,iz;
  float jx,jy,jz;
  float tx,ty,tz;
  float d2;
  float d6;
  float d2inv;
  float d6inv;
  float d12inv;
  float sh1;
  float sh2;
  float sw;
  float sw1;
  float frac;
  float nbvdw;
  float A,B;
  int tc1,tc2;
  int data_pos;
  const float c2diffinv = 1.0/((c2-c_on2)*(c2-c_on2)*(c2-c_on2));
  const float one = 1.0;
  const float two = 2.0;
  const float three = 3.0;
  const float four = 4.0;
  const float six_inv = 1.0/6.0; 
  const float twelve_inv = 1.0/12.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    b1 = boundarry[2*i];
    b2 = boundarry[2*i+1];
    fracX = 0;
    fracY = 0;
    fracZ = 0;
    fpos = COOR_DIM*f;
    ix = coor[fpos];
    iy = coor[fpos+1];
    iz = coor[fpos+2];
    tc1 = type_code[f];
    for(j= b1;j<b2;j++){
      s = second[j];
      spos = COOR_DIM*s;
      jx = coor[spos];
      jy = coor[spos+1];
      jz = coor[spos+2];
      dx = ix-jx;
      dy = iy-jy;
      dz = iz-jz;
      d2 = dx*dx+dy*dy+dz*dz;
      if(d2<c2){
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	//	d2inv = one/d2;
	//	dinv = sqrt(d2inv);
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	d6 = d2*d2*d2;
	nbvdw = A*d12inv - B*d6inv;
	if(d2>c_on2){
	  sh1 = c2-d2;
	  sh2 = (c2+two*d2-three*c_on2);
	  sw = sh1*sh2;
	  sw1= four*(sh1-sh2);
	  frac = nbvdw*sw*d2inv-(twelve_inv*A*d12inv-six_inv*B*d6inv)*sw1;
	  frac = frac*c2diffinv*sh1;
	}
	else frac = nbvdw*d2inv;
	tx = frac*dx;
	ty = frac*dy;
	tz = frac*dz;
	fracX = fracX - tx;
	fracY = fracY - ty;
	fracZ = fracZ - tz;
	force[spos] = force[spos] + tx;
	force[spos+1] = force[spos+1] + ty;
	force[spos+2] = force[spos+2] + tz;
      }
    }
    force[fpos] = force[fpos] + fracX;
    force[fpos+1] = force[fpos+1] + fracY;
    force[fpos+2] = force[fpos+2] + fracZ;
  }
}