CubicSpline.hpp

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 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
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 * work.  Good starting points are:
 *
 * [1] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
 * [2] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
 * [3] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
 * [4] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
 * [5] Kuang & Gezelter, Mol. Phys., 110, 691-701 (2012).
 * [6] Lamichhane, Gezelter & Newman, J. Chem. Phys. 141, 134109 (2014).
 * [7] Lamichhane, Newman & Gezelter, J. Chem. Phys. 141, 134110 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 */
 
#ifndef MATH_CUBICSPLINE_HPP
#define MATH_CUBICSPLINE_HPP
 
#include <config.h>
 
#include <memory>
#include <utility>
#include <vector>
 
using namespace std;
namespace OpenMD {
 
  class CubicSpline {
  public:
    CubicSpline();
    virtual ~CubicSpline() {}
    void addPoint(const RealType xp, const RealType yp);
    void addPoints(const std::vector<RealType>& xps,
                   const std::vector<RealType>& yps);
    RealType getValueAt(const RealType& t);
    std::pair<RealType, RealType> getLimits();
    void getValueAt(const RealType& t, RealType& v);
    void getValueAndDerivativeAt(const RealType& t, RealType& v, RealType& d);
    RealType getSpacing();
 
  private:
    void generate();
    std::vector<int> sort_permutation(std::vector<RealType>& v);
    std::vector<RealType> apply_permutation(std::vector<RealType> const& v,
                                            std::vector<int> const& p);
 
    bool isUniform;
    bool generated;
    RealType dx, dt;
    int n, j;
    std::vector<RealType> x_;
    std::vector<RealType> y_;
    std::vector<RealType> b;
    std::vector<RealType> c;
    std::vector<RealType> d;
  };
 
  class Comparator {
    std::vector<RealType>& _v;
 
  public:
    Comparator(std::vector<RealType>& v) : _v(v) {}
    bool operator()(size_t i, size_t j) { return _v[i] < _v[j]; }
  };
 
  using CubicSplinePtr = std::shared_ptr<CubicSpline>;
}  // namespace OpenMD
 
#endif