double Ewald::Adjust(double q0, double q1, double rij) {
t_adjust_.Start();
t_erfc_.Start();
//double erfc = erfc_func(ew_coeff_ * rij);
double erfc = ERFC(ew_coeff_ * rij);
t_erfc_.Stop();
double d0 = (erfc - 1.0) / rij;
t_adjust_.Stop();
return (q0 * q1 * d0);
}
/*
The function <p> from the paper (probability of collision of 2
points for 1 LSH function).
*/
RealT computeFunctionP(RealT w, RealT c){
// Pi:
if ( c < Pi_EPSILON ) // c is close to zero; x->inf; then:
// assume erfc(inf)->0, the second part->0
return 1.; // c->0 means the points should always conflict.
else {
RealT x = w / c;
return 1 - ERFC(x / M_SQRT2) - M_2_SQRTPI / M_SQRT2 / x * (1 - EXP(-SQR(x) / 2));
}
}
/** Calculate direct space energy. This is the slow version that doesn't
* use a pair list; for debug purposes only.
*/
double Ewald::Direct(Matrix_3x3 const& ucell, Topology const& tIn, AtomMask const& mask)
{
t_direct_.Start();
double cut2 = cutoff_ * cutoff_;
double Eelec = 0.0;
Varray const& Image = pairList_.ImageCoords();
Varray const& Frac = pairList_.FracCoords();
unsigned int maxidx = Image.size();
for (unsigned int idx1 = 0; idx1 != maxidx; idx1++)
{
// Set up coord for this atom
Vec3 const& crd1 = Image[idx1];
// Set up exclusion list for this atom
int atom1 = mask[idx1];
Atom::excluded_iterator excluded_atom = tIn[atom1].excludedbegin();
for (unsigned int idx2 = idx1 + 1; idx2 != maxidx; idx2++)
{
int atom2 = mask[idx2];
// If atom is excluded, just increment to next excluded atom.
if (excluded_atom != tIn[atom1].excludedend() && atom2 == *excluded_atom) {
++excluded_atom;
//mprintf("ATOM: Atom %4i to %4i excluded.\n", atom1+1, atom2+1);
} else {
// Only need to check nearest neighbors.
Vec3 const& frac2 = Frac[idx2];
for (Varray::const_iterator ixyz = Cells_.begin(); ixyz != Cells_.end(); ++ixyz)
{
Vec3 dxyz = ucell.TransposeMult(frac2 + *ixyz) - crd1;
double rij2 = dxyz.Magnitude2();
if ( rij2 < cut2 ) {
double rij = sqrt( rij2 );
// Coulomb
double qiqj = Charge_[idx1] * Charge_[idx2];
t_erfc_.Start();
//double erfc = erfc_func(ew_coeff_ * rij);
double erfc = ERFC(ew_coeff_ * rij);
t_erfc_.Stop();
double e_elec = qiqj * erfc / rij;
Eelec += e_elec;
//mprintf("EELEC %4i%4i%12.5f%12.5f%12.5f%3.0f%3.0f%3.0f\n",
// mprintf("EELEC %6i%6i%12.5f%12.5f%12.5f\n", atom1, atom2, rij, erfc, e_elec);
// TODO can we break here?
} //else
//mprintf("ATOM: Atom %4i to %4i outside cut, %6.2f > %6.2f %3.0f%3.0f%3.0f\n",
//mprintf("ATOM: Atom %4i to %4i outside cut, %6.2f > %6.2f\n",
// atom1, atom2,sqrt(rij2),cutoff_);
}
}
}
}
t_direct_.Stop();
return Eelec;
}
/*
The function <p> from the paper (probability of collision of 2
points for 1 LSH function).
*/
RealT computeFunctionP(RealT w, RealT c){ //L2 norm //两个点在一个桶中冲突的可能性 p1 //c为什么设为1
RealT x = w / c;
return 1 - ERFC(x / M_SQRT2) - M_2_SQRTPI / M_SQRT2 / x * (1 - EXP(-SQR(x) / 2)); //ERFC为余误差函数，M_SQRT2为math.h中的函数，值为pi
//M_2_SQRTPI= 2/sqrt(pi) ,exp(x)=e^x 程序公式1
}
/*
The function <p> from the paper (probability of collision of 2
points for 1 LSH function).
*/
RealT computeFunctionP(RealT w, RealT c){
RealT x = w / c;
return 1 - ERFC(x / M_SQRT2) - M_2_SQRTPI / M_SQRT2 / x * (1 - EXP(-SQR(x) / 2));
}
single XERFC( single *arg ) {
//===========================
return( ERFC( *arg ) );
}
double Ewald::Adjust(double q0, double q1, double rij) const {
double erfc = ERFC(ew_coeff_ * rij);
double d0 = (erfc - 1.0) / rij;
return (q0 * q1 * d0);
}
