/***************************************************************************
                          enefuncvdw.c  -  description
                             -------------------
    begin                : Fri Mar 18 12:25:31 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


//xxsn
void energy_xxsn_d(const int * first,
		   const int * second,
		   const int * boundarry,
		   const int natoms,
		   const double * coor,
		   const double  c2,
		   const double c_on2,
		   const int * type_code,
		   const int type_size,
		   const double * vdw_data,
		   double * ene_vdw,  double *ene_cul){

  int f;
  int fpos;
  int s;
  int spos;
  double dx,dy,dz;
  double ix,iy,iz;
  double jx,jy,jz;
  double d2;
  double d6;
  double d2inv;
  double d6inv;
  double d12inv;
  double shiftf;
  double A,B;
  int tc1,tc2;
  int data_pos;
  double nb6;
  double nb12;
  double evdw =0;

  const double c2inv = 1.0/c2;
  const double c6inv = c2inv*c2inv*c2inv;
  const double c12inv = c6inv*c6inv;
  const double one = 1.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    fpos = COOR_DIM*f;
    int b1 = boundarry[2*i];
    int b2 = boundarry[2*i+1];
    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) continue;
      //	  if(d2>c2){ cout<<"AHHHHHHHHHH"<<endl;}
      {
	//compute energy
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	//now energy
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	d6 = d2*d2*d2;
	shiftf = one - d6*c6inv;
	nb12 = A*(d12inv - c12inv*(one + shiftf+shiftf));
	nb6 = B*(d6inv -c6inv*(one + shiftf));
	evdw  = evdw +
	  nb12 - nb6;
      }
    }
  }
      
  *ene_vdw = *ene_vdw + evdw;
}


void energy_xxsn_f(const int * first,
		   const int * second,
		   const int * boundarry,
		   const int natoms,
		   const float * coor,
		   const float  c2,
		   const float  c2_on,
		   const int * type_code,
		   const int type_size,
		   const float * vdw_data,
		   float * ene_vdw, float *ene_cul){

  int f;
  int fpos;
  int s;
  int spos;
  float dx,dy,dz;
  float ix,iy,iz;
  float jx,jy,jz;
  float d2;
  float d6;
  float d2inv;
  float d6inv;
  float d12inv;
  float shiftf;
  float A,B;
  int tc1,tc2;
  int data_pos;
  float nb6;
  float nb12;
  float evdw =0;

  const float c2inv = 1.0/c2;
  const float c6inv = c2inv*c2inv*c2inv;
  const float c12inv = c6inv*c6inv;
  const float one = 1.0;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    fpos = COOR_DIM*f;
    int b1 = boundarry[2*i];
    int b2 = boundarry[2*i+1];
    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) continue;
      //	  if(d2>c2){ cout<<"AHHHHHHHHHH"<<endl;}
      {
	//compute energy
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	//now energy
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	d6 = d2*d2*d2;
	shiftf = one - d6*c6inv;
	nb12 = A*(d12inv - c12inv*(one + shiftf+shiftf));
	nb6 = B*(d6inv -c6inv*(one + shiftf));
	evdw  = evdw +
	  nb12 - nb6;
      }
    }
  }
      
  *ene_vdw = *ene_vdw + evdw;
}


//xxswn
void 
energy_xxswn_d(const int * first,
	       const int * second,
	       const int * boundarry,
	       const int natoms,
	       const double * coor,
	       const double  c2,
	       const double  c_on2,
	       const int * type_code,
	       const int type_size,
	       const double * vdw_data,
	       double *ene_vdw, double * ene_cul){
  int f;
  int fpos;
  int s;
  int spos;
  double dx,dy,dz;
  double ix,iy,iz;
  double jx,jy,jz;
  double d2;
  double d2inv;
  double d6inv;
  double d12inv;
  double switchf;
  double A,B;
  int tc1,tc2;
  int data_pos;
  double nb6;
  double nb12;
  double evdw =0;

  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;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    fpos = COOR_DIM*f;
    int b1 = boundarry[2*i];
    int b2 = boundarry[2*i+1];
    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) continue;
      {
	//compute energy
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	//now energy
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	nb12 = A*(d12inv);
	nb6 = B*(d6inv);
	if(d2>c_on2){
	  switchf = c2diffinv*(c2-d2)*(c2-d2)*(c2+two*d2-three*c_on2);
	  evdw  = evdw +
	    (nb12 - nb6)*switchf;	  
	}
	else {
	  evdw  = evdw + (nb12 - nb6);
	}
      }
    }
  }
      
  *ene_vdw = *ene_vdw + evdw;
}


void 
energy_xxswn_f(const int * first,
	       const int * second,
	       const int * boundarry,
	       const int natoms,
	       const float * coor,
	       const float  c2,
	       const float  c_on2,
	       const int * type_code,
	       const int type_size,
	       const float * vdw_data,	       
	       float * ene_vdw,
	       float * ene_cul){
  int f;
  int fpos;
  int s;
  int spos;
  float dx,dy,dz;
  float ix,iy,iz;
  float jx,jy,jz;
  float d2;
  float d2inv;
  float d6inv;
  float d12inv;
  float switchf;
  float A,B;
  int tc1,tc2;
  int data_pos;
  float nb6;
  float nb12;
  float evdw =0;

  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;
  int i,j;
  for(i = 0;i<natoms;i++){
    f = first[i];
    fpos = COOR_DIM*f;
    int b1 = boundarry[2*i];
    int b2 = boundarry[2*i+1];
    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) continue;
      {
	//compute energy
	tc2 = type_code[s];
	data_pos = 4*(type_size*tc1+tc2);
	A = vdw_data[data_pos];
	B = vdw_data[data_pos+1];
	//now energy
	d2inv = one/d2;
	d6inv = d2inv*d2inv*d2inv;
	d12inv = d6inv*d6inv;
	nb12 = A*(d12inv);
	nb6 = B*(d6inv);
	if(d2>c_on2){
	  switchf = c2diffinv*(c2-d2)*(c2-d2)*(c2+two*d2-three*c_on2);
	  evdw  = evdw +
	    (nb12 - nb6)*switchf;	  
	}
	else {
	  evdw  = evdw + (nb12 - nb6);
	}
      }
    }
  }
      
  *ene_vdw = *ene_vdw + evdw;
}