FGRungeKutta.h

/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 Header:       FGRungeKutta.h
 Author:       Thomas Kreitler
 Date started: 04/9/2010
 
 ------------- Copyright (C)  -------------
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU Lesser General Public License as published by the Free Software
 Foundation; either version 2 of the License, or (at your option) any later
 version.
 
 This program 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 Lesser General Public License for more
 details.
 
 You should have received a copy of the GNU Lesser General Public License along with
 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 Place - Suite 330, Boston, MA  02111-1307, USA.
 
 Further information about the GNU Lesser General Public License can also be found on
 the world wide web at http://www.gnu.org.
 
HISTORY
--------------------------------------------------------------------------------
 
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
SENTRY
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
#ifndef FGRUNGEKUTTA_H
#define FGRUNGEKUTTA_H
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
namespace JSBSim {
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS DOCUMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DECLARATION: FGRungeKuttaProblem
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
class FGRungeKuttaProblem {
  public:
    virtual double pFunc(double x, double y) = 0;
};
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DECLARATION: FGRungeKutta
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
class FGRungeKutta {
 
  public:
 
    enum eStates { eNoError=0, eMathError=1, eFaultyInit=2, eEvolve=4, eUnknown=8} ;
 
    int init(double x_start, double x_end, int intervals = 4);
 
    double evolve(double y_0, FGRungeKuttaProblem *pf);
 
    double getXEnd()      { return x_end; }
    double getError()     { return err; }
 
    int  getStatus()      { return status; }
    int  getIterations()  { return iterations; }
    void clearStatus()    { status = eNoError; }
    void setTrace(bool t) { trace_values = t; }
 
  protected:
    // avoid accidents
    FGRungeKutta():  status(eNoError), trace_values(false), iterations(0) {};
    virtual ~FGRungeKutta();
 
    FGRungeKuttaProblem *pfo;
 
    double h;
    double h05;  // h*0.5, halfwidth
    double err;
 
  private:
 
    virtual double approximate(double x, double y) = 0;
 
    bool sane_val(double x);
 
    static const double RealLimit;
 
    double x0, x1;
    double safer_x1;
    double x_end;
 
    int status;
    bool trace_values;
    int iterations;
 
};
 
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DECLARATION: FGRK4
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
class FGRK4 : public FGRungeKutta {
    virtual ~FGRK4();
  private:
    double approximate(double x, double y);
};
 
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DECLARATION: FGRKFehlberg
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
class FGRKFehlberg : public FGRungeKutta {
 
  public:
    FGRKFehlberg() : shrink_avail(4), epsilon(1e-12) { };
    virtual ~FGRKFehlberg();
    double getEpsilon()          { return epsilon; }
    int    getShrinkAvail()      { return shrink_avail; }
    void   setEpsilon(double e)  { epsilon = e; }
    void   setShrinkAvail(int s) { shrink_avail = s; }
 
  private:
 
    double approximate(double x, double y);
 
    int    shrink_avail;
    double epsilon;
 
    static const double A2[], A3[], A4[], A5[], A6[];
    static const double B[],  Bs[], C[];
 
};
 
 
} // namespace JSBSim
 
#endif