G4INCLRootFinder.hh

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//
// INCL++ intra-nuclear cascade model
// Pekka Kaitaniemi, CEA and Helsinki Institute of Physics
// Davide Mancusi, CEA
// Alain Boudard, CEA
// Sylvie Leray, CEA
// Joseph Cugnon, University of Liege
//
// INCL++ revision: v5.1.8
//
#define INCLXX_IN_GEANT4_MODE 1
 
#include "globals.hh"
 
/** \file G4INCLRootFinder.hh
 * \brief Static root-finder algorithm.
 *
 * Provides a (nearly) stateless root-finder algorithm.
 *
 * \date 2nd March 2011
 * \author Davide Mancusi
 */
 
#ifndef G4INCLROOTFINDER_HH_
#define G4INCLROOTFINDER_HH_
 
#include <utility>
#include "G4INCLIFunction1D.hh"
 
namespace G4INCL {
 
  class RootFunctor : public IFunction1D {
  public:
    virtual void cleanUp(const G4bool success) const = 0;
    virtual ~RootFunctor() {};
  protected:
    RootFunctor(const G4double x0, const G4double x1) :
      IFunction1D(x0, x1)
    {};
  };
 
  class RootFinder {
  public:
    /** \brief Numerically solve a one-dimensional equation.
     *
     * Numerically solves the equation f(x)==0. This implementation uses the
     * false-position method.
     *
     * If a root is found, it can be retrieved using the getSolution() method,
     *
     * \param f pointer to a RootFunctor
     * \param x0 initial value of the function argument
     * \return true if a root was found
     */
    static G4bool solve(RootFunctor const * const f, const G4double x0);
 
    /** \brief Get the solution of the last call to solve().
     *
     * \return the solution, as an (x,y) pair
     */
    static std::pair<G4double,G4double> const &getSolution() { return RootFinder::solution; }
 
  private:
    /// \brief The solution obtained in the last call to solve().
    static std::pair<G4double,G4double> solution;
 
    /** \brief Bracket the root of the function f.
     *
     * Tries to find a bracketing value for the function root.
     *
     * \param f pointer to a RootFunctor
     * \param x0 starting value
     * \return if the root could be bracketed, returns two values of x
     *   bracketing the root, as a pair. If the bracketing failed, returns a
     *   pair with first > second.
     */
    static std::pair<G4double,G4double> bracketRoot(RootFunctor const * const f, const G4double x0);
 
    /// \brief Maximum number of iterations for convergence
    static const G4int maxIterations=50;
 
    /// \brief Tolerance on the y value
    static const G4double toleranceY;
 
  protected:
    RootFinder() {};
    ~RootFinder() {};
    
  };
}
#endif /* G4INCLROOTFINDER_HH_ */