lineSearch.h

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// -*- Mode: C++; tab-width: 2; -*-
// vi: set ts=2:
//
// $Id: lineSearch.h,v 1.20.18.3 2007/08/07 09:12:34 aleru Exp $
//

// Line Search Minimizer: A special class for the line search minimization algorithm

#ifndef BALL_MOLMEC_MINIMIZATION_LINESEARCH_H
#define BALL_MOLMEC_MINIMIZATION_LINESEARCH_H

#ifndef BALL_COMMON_H
# include <BALL/common.h>
#endif

namespace BALL 
{
  class EnergyMinimizer;

  class BALL_EXPORT LineSearch
  {
    public:
      
      
      BALL_CREATE(LineSearch)
      
      
      LineSearch();
      
      LineSearch(EnergyMinimizer& minimizer);
      
      LineSearch(const LineSearch& line_search);
      
      virtual ~LineSearch() ;
      

      
      const LineSearch& operator=(const LineSearch& LineSearch);
      

      
      void setAlpha(double alpha);
      
      void setBeta(double beta);
      
      double getAlpha() const;
      
      double getBeta() const;
      
      Size getMaxSteps() const;
      
      void setMaxSteps(Size steps);
      
      void setLowerBound(double lbound);
      
      double getLowerBound() const;
      
      void setXTol(double xtol);
      
      double getXTol() const;
      
      void setBracketedFlag(bool bracktd);
    
      bool isBracketed() const;
      
    void setMinimizer(EnergyMinimizer& minimizer);
      
      virtual void takeStep(double &st_a, double &f_a, double &g_a, double &st_b, double &f_b, 
                 double &g_b, double &stp, double f, double g, double minstp, double maxstp);
      

      
      virtual bool minimize(double& stp, bool keep_gradient = false);
      
    protected:
      
      /*_ Parameter alpha for line search criterion.
      */
      double alpha_;
      
      /*_ Parameter beta for line search criterion.
      */
      double beta_;
      
      /*_ Parameter for the number of interpolation steps
      */
      Size max_steps_;
      
      /*_ Lower bound for energy values.
      */
      double lower_energy_bound_;
      
      /*_ Nonnegative relative tolerance for an acceptable step.
      */
      double stptol_;
      
      /*_ Specifies whether a minimizer has already been bracketed or not.
      */
      bool is_bracketed_;
      
      /*_ Calling minimizer class which provides the search direction among other things.
      */
      EnergyMinimizer* minimizer_;
    
  };
  
} // namespace BALL

#endif // BALL_MOLMEC_MINIMIZATION/LINESEARCH_H