////////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2011 The Regents of the University of California
//
// This file is part of Qbox
//
// Qbox is distributed under the terms of the GNU General Public License
// as published by the Free Software Foundation, either version 2 of
// the License, or (at your option) any later version.
// See the file COPYING in the root directory of this distribution
// or <http://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////////////
//
// LineMinimizer.h
//
////////////////////////////////////////////////////////////////////////////////

#ifndef LINEMINIMIZER_H
#define LINEMINIMIZER_H

class LineMinimizer
{
  private:

  double f0,fp0,fm,fpm,f_low,fp_low,f_high,fp_high,
         alpha_m,alpha_low,alpha_high;
  bool first_use, done_, fail_, bracketing, use_psi;
  bool debug_print;
  double alpha_start_, alpha_max_, sigma1_, sigma2_;
  int nstep_, nstep_max_;

  double psi(double alpha, double f) { return f - f0 - alpha * fp0 * sigma1_; }
  double psip(double fp) { return fp - fp0 * sigma1_; }
  double interpolate(void);

  public:

  LineMinimizer(void) : sigma1_(0.1), sigma2_(0.5), alpha_start_(0.1),
   alpha_max_(1.0), first_use(true), done_(false), fail_(false),
   bracketing(false), use_psi(true), nstep_(0), nstep_max_(5),
   debug_print(false) {}
  void reset(void) { first_use = true; done_ = false; fail_ = false;
    bracketing = false; nstep_ = 0; }
  double sigma1(void) const { return sigma1_; }
  double sigma2(void) const { return sigma2_; }
  double alpha_start(void) const { return alpha_start_; }
  double alpha_max(void) const { return alpha_max_; }
  bool done(void) const { return done_; }
  bool fail(void) const { return fail_; }

  void set_sigma1(double s) { sigma1_ = s; }
  void set_sigma2(double s) { sigma2_ = s; }
  void set_alpha_start(double a) { alpha_start_ = a; }
  void set_alpha_max(double a) { alpha_max_ = a; }
  void set_debug_print(void) { debug_print = true; }

  double next_alpha(double alpha, double f, double fp);
};
#endif