CompactFunction.h

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// n2p2 - A neural network potential package
// Copyright (C) 2018 Andreas Singraber (University of Vienna)
// Copyright (C) 2020 Martin P. Bircher
//
// 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 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
#ifndef COMPACTFUNCTION_H
#define COMPACTFUNCTION_H
 
#include "CoreFunction.h"
 
namespace nnp
{

class CompactFunction
{
public:
    CompactFunction();
    void               setCoreFunction(CoreFunction::Type const type);
    void               setCenterWidth(double center, double width);
    void               setLeftRight(double left, double right);
    CoreFunction::Type getCoreFunctionType() const;
#ifndef N2P2_NO_ASYM_POLY
    void               setAsymmetric(bool asymmetric);
    bool               getAsymmetric() const;
#endif
    double             getCenter() const;
    double             getWidth() const;
    double             getLeft() const;
    double             getRight() const;
    double             f(double a) const;
    double             df(double a) const;
    void               fdf(double a, double& fa, double& dfa) const;
 
private:
    double       center;
    double       width;
    double       left;
    double       right;
    double       scale;
    CoreFunction core;
 
};

// Inlined function definitions //
 
inline void CompactFunction::setCoreFunction(CoreFunction::Type const type)
{
    core.setType(type);
 
    return;
}
 
inline CoreFunction::Type CompactFunction::getCoreFunctionType() const
{
    return core.getType();
}
 
inline double CompactFunction::getCenter() const { return center; }
inline double CompactFunction::getWidth() const { return width; }
inline double CompactFunction::getLeft() const { return left; }
inline double CompactFunction::getRight() const { return right; }
 
inline double CompactFunction::f(double a) const
{
    a = (a - center) * scale;
    return core.f(std::abs(a));
}
 
inline double CompactFunction::df(double a) const
{
    a = (a - center) * scale;
    return copysign(scale * core.df(std::abs(a)), a);
}
 
inline void CompactFunction::fdf(double a, double& fa, double& dfa) const
{
    a = (a - center) * scale;
    core.fdf(std::abs(a), fa, dfa);
    dfa *= copysign(scale, a);
 
    return;
}
 
 
}
 
#endif