double SwitchingFunction::calculate(double distance,double&dfunc)const{
plumed_massert(init,"you are trying to use an unset SwitchingFunction");
if(distance>dmax){
dfunc=0.0;
return 0.0;
}
const double rdist = (distance-d0)*invr0;
double result;
if(rdist<=0.){
result=1.;
dfunc=0.0;
}else{
if(type==smap){
double sx=c*pow( rdist, a );
result=pow( 1.0 + sx, d );
dfunc=-b*sx/rdist*result/(1.0+sx);
} else if(type==rational){
result=do_rational(rdist,dfunc,nn,mm);
}else if(type==exponential){
result=exp(-rdist);
dfunc=-result;
}else if(type==nativeq){
double rdist2 = beta*(distance - lambda * ref);
double exprdist=exp(rdist2);
result=1./(1.+exprdist);
dfunc=-exprdist/(1.+exprdist)/(1.+exprdist);
}else if(type==gaussian){
result=exp(-0.5*rdist*rdist);
dfunc=-rdist*result;
}else if(type==cubic){
double tmp1=rdist-1, tmp2=(1+2*rdist);
result=tmp1*tmp1*tmp2;
dfunc=2*tmp1*tmp2 + 2*tmp1*tmp1;
}else if(type==tanh){
double tmp1=std::tanh(rdist);
result = 1.0 - tmp1;
dfunc=-(1-tmp1*tmp1);
#ifdef __PLUMED_HAS_MATHEVAL
}else if(type==matheval){
result=evaluator_evaluate_x(evaluator,rdist);
dfunc=evaluator_evaluate_x(evaluator_deriv,rdist);
#endif
}else plumed_merror("Unknown switching function type");
// this is for the chain rule:
dfunc*=invr0;
// this is because calculate() sets dfunc to the derivative divided times the distance.
// (I think this is misleading and I would like to modify it - GB)
dfunc/=distance;
}
result=result*stretch+shift;
dfunc*=stretch;
return result;
}
double SwitchingFunction::calculateSqr(double distance2,double&dfunc)const{
if(type==rational && nn%2==0 && mm%2==0 && d0==0.0){
if(distance2>dmax_2){
dfunc=0.0;
return 0.0;
}
const double rdist_2 = distance2*invr0_2;
double result=do_rational(rdist_2,dfunc,nn/2,mm/2);
// chain rule:
dfunc*=2*invr0_2;
// stretch:
result=result*stretch+shift;
dfunc*=stretch;
return result;
} else {
double distance=std::sqrt(distance2);
return calculate(distance,dfunc);
}
}
double SwitchingFunction::calculate(double distance,double&dfunc)const{
plumed_massert(init,"you are trying to use an unset SwitchingFunction");
if(distance>dmax){
dfunc=0.0;
return 0.0;
}
const double rdist = (distance-d0)*invr0;
double result;
if(rdist<=0.){
result=1.;
dfunc=0.0;
}else{
if(type==smap){
double sx=c*pow( rdist, a );
result=pow( 1.0 + sx, d );
dfunc=-b*sx/rdist*result/(1.0+sx);
} else if(type==rational){
result=do_rational(rdist,dfunc,nn,mm);
}else if(type==exponential){
result=exp(-rdist);
dfunc=-result;
}else if(type==gaussian){
result=exp(-0.5*rdist*rdist);
dfunc=-rdist*result;
}else plumed_merror("Unknown switching function type");
// this is for the chain rule:
dfunc*=invr0;
// this is because calculate() sets dfunc to the derivative divided times the distance.
// (I think this is misleading and I would like to modify it - GB)
dfunc/=distance;
}
result=result*stretch+shift;
dfunc*=stretch;
return result;
}
