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 // @(#)root/mathmore:$Id$
 // Author: L. Moneta Thu Jan 25 11:13:48 2007
 
 /**********************************************************************
  *                                                                    *
  * Copyright (c) 2006  LCG ROOT Math Team, CERN/PH-SFT                *
  *                                                                    *
  * This library 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 2     *
  * of the License, or (at your option) any later version.             *
  *                                                                    *
  * This library 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 library (see file COPYING); if not, write          *
  * to the Free Software Foundation, Inc., 59 Temple Place, Suite      *
  * 330, Boston, MA 02111-1307 USA, or contact the author.             *
  *                                                                    *
  **********************************************************************/
 
 // Header file for class GSLSimAnnealing
 
 #ifndef ROOT_Math_GSLSimAnnealing
 #define ROOT_Math_GSLSimAnnealing
 
 #include "Math/IFunctionfwd.h"
 
 #include <algorithm>
 #include <vector>
 
 namespace ROOT {
 
    namespace Math {
 
       class GSLRandomEngine;
 
 //_____________________________________________________________________________
 /**
    GSLSimAnFunc class description.
    Interface class for the  objetive function to be used in simulated annealing
    If user wants to re-implement some of the methods (like the one defining the metric) which are used by the
    the simulated annealing algorithm must build a user derived class.
    NOTE: Derived classes must re-implement the assignment and copy constructor to call them of the parent class
 
    @ingroup MultiMin
  */
 class GSLSimAnFunc {
 public:
 
    /**
       construct from an interface of a multi-dimensional function
     */
    GSLSimAnFunc(const ROOT::Math::IMultiGenFunction & func, const double * x);
 
    /**
       construct from an interface of a multi-dimensional function
       Use optionally a scale factor (for each coordinate) which can  be used to scale the step sizes
       (this is used for example by the minimization algorithm)
     */
    GSLSimAnFunc(const ROOT::Math::IMultiGenFunction & func, const double * x, const double * scale);
 
 protected:
 
    /**
       derived classes might need to re-define completely the class
     */
    GSLSimAnFunc() :
       fFunc(nullptr)
    {}
 
 public:
 
 
    /// virtual destructor (no operations)
    virtual ~GSLSimAnFunc() { } //
 
 
    /**
       fast copy method called by GSL simulated annealing internally
       copy only the things which have been changed
       must be re-implemented by derived classes if needed
    */
    virtual GSLSimAnFunc & FastCopy(const GSLSimAnFunc & f);
 
 
    /**
       clone method. Needs to be re-implemented by the derived classes for deep  copying
     */
    virtual GSLSimAnFunc * Clone() const {
       return new GSLSimAnFunc(*this);
    }
 
    /**
       evaluate the energy ( objective function value)
       re-implement by derived classes if needed to be modified
     */
    virtual double Energy() const;
 
    /**
       change the x[i] value using a random value urndm generated between [0,1]
       up to a maximum value maxstep
       re-implement by derived classes if needed to be modified
     */
    virtual void Step(const GSLRandomEngine & r, double maxstep);
 
    /**
       calculate the distance (metric) between  this one and another configuration
       Presently a cartesian metric is used.
       re-implement by derived classes if needed to be modified
     */
    virtual double Distance(const GSLSimAnFunc & func) const;
 
    /**
       print the position in the standard output std::ostream
       GSL prints in addition n iteration, n function calls, temperature and energy
       re-implement by derived classes if necessary
     */
    virtual void Print();
 
    /**
        change the x values (used by sim annealing to take a step)
     */
    void SetX(const double * x) {
       std::copy(x, x+ fX.size(), fX.begin() );
    }
 
    template <class IT>
    void SetX(IT begin, IT end) {
       std::copy(begin, end, fX.begin() );
    }
 
    unsigned int NDim() const { return fX.size(); }
 
    double X(unsigned int i) const { return fX[i]; }
 
    const std::vector<double> &  X() const { return fX; }
 
    double Scale(unsigned int i) const { return fScale[i]; }
 
    void SetX(unsigned int i, double x) { fX[i] = x; }
 
    // use compiler generated  copy ctror and assignment operators
 
 private:
 
    std::vector<double>  fX;
    std::vector<double>  fScale;
    const ROOT::Math::IMultiGenFunction * fFunc;
 
 };
 
 //_____________________________________________________
 /**
     structure holding the simulated annealing parameters
 
    @ingroup MultiMin
 */
 struct GSLSimAnParams {
 
    // constructor with some default values
    GSLSimAnParams() {
       n_tries =    200;
       iters_fixed_T =  10;
       step_size =   10;
       // the following parameters are for the Boltzmann distribution */
       k = 1.0;
       t_initial =  0.002;
       mu_t =  1.005;
       t_min = 2.0E-6;
    }
 
 
    int n_tries;            // number of points to try for each step
    int iters_fixed_T;      // number of iterations at each temperature
    double step_size;       // max step size used in random walk
    /// parameters for the Boltzman distribution
    double k;
    double t_initial;
    double mu_t;
    double t_min;
 };
 
 //___________________________________________________________________________
 /**
    GSLSimAnnealing class for performing  a simulated annealing search of
    a multidimensional function
 
    @ingroup MultiMin
 */
 class GSLSimAnnealing {
 
 public:
 
    /**
       Default constructor
    */
    GSLSimAnnealing ();
 
    /**
       Destructor (no operations)
    */
    ~GSLSimAnnealing ()  {}
 
    // usually copying is non trivial, so we delete this
    GSLSimAnnealing(const GSLSimAnnealing &) = delete;
    GSLSimAnnealing & operator = (const GSLSimAnnealing & rhs) = delete;
    GSLSimAnnealing(GSLSimAnnealing &&) = delete;
    GSLSimAnnealing & operator = (GSLSimAnnealing && rhs) = delete;
 
    /**
       solve the simulated annealing given a multi-dim function, the initial vector parameters
       and a vector containing the scaling factors for the parameters
    */
    int Solve(const ROOT::Math::IMultiGenFunction & func, const double * x0, const double * scale, double * xmin, bool debug = false);
 
    /**
       solve the simulated annealing given a GSLSimAnFunc object
       The object will contain the initial state at the beginning and the final minimum state at the end
    */
    int Solve(GSLSimAnFunc & func, bool debug = false);
 
 
    GSLSimAnParams & Params() { return fParams; }
    const GSLSimAnParams & Params() const { return fParams; }
    void SetParams(const GSLSimAnParams & params) { fParams = params; }
 
 private:
 
    GSLSimAnParams fParams; // parameters for GSLSimAnnealig
 
 };
 
    } // end namespace Math
 
 } // end namespace ROOT
 
 
 #endif /* ROOT_Math_GSLSimAnnealing */

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