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 /*
     SPDX-FileCopyrightText: 2007 Vladimir Kuznetsov <ks.vladimir@gmail.com>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 
 /** \file eulersolver.h
  *  \brief GenericEulerSolver, EulerSolver and AdaptiveEulerSolver classes
  */
 
 #ifndef STEPCORE_EULERSOLVER_H
 #define STEPCORE_EULERSOLVER_H
 
 #include "solver.h"
 #include "object.h"
 
 namespace StepCore {
 
 /** \ingroup solvers
  *  \brief Adaptive and non-adaptive Euler solver with error estimation
  *  
  *  See https://en.wikipedia.org/wiki/Numerical_ordinary_differential_equations#The_Euler_method
  *  and https://en.wikipedia.org/wiki/Adaptive_step_size
  *
  *  \todo tests
  */
 class GenericEulerSolver: public Solver
 {
     STEPCORE_OBJECT(GenericEulerSolver)
 
 public:
     /** Constructs GenericEulerSolver */
     GenericEulerSolver(double stepSize, bool adaptive)
         : Solver(stepSize), _adaptive(adaptive) { init(); }
     /** Constructs GenericEulerSolver */
     GenericEulerSolver(int dimension, Function function,
             void* params, double stepSize, bool adaptive)
         : Solver(dimension, function, params, stepSize),
             _adaptive(adaptive) { init(); }
     /** Copy constructor */
     GenericEulerSolver(const GenericEulerSolver& eulerSolver)
         : Solver(eulerSolver), _adaptive(eulerSolver._adaptive) { init(); }
 
     ~GenericEulerSolver() { fini(); }
 
     void setDimension(int dimension) override { fini(); _dimension = dimension; init(); }
 
     int doCalcFn(double* t, const VectorXd* y, const VectorXd* yvar = nullptr,
                         VectorXd* f = nullptr, VectorXd* fvar = nullptr) override;
     int doEvolve(double* t, double t1, VectorXd* y, VectorXd* yvar) override;
 
 protected:
     int doStep(double t, double stepSize, VectorXd* y, VectorXd* yvar);
     void init();
     void fini();
 
     bool    _adaptive;
     VectorXd _yerr;
     VectorXd _ytemp;
     VectorXd _ydiff;
     VectorXd _ytempvar;
     VectorXd _ydiffvar;
 };
 
 /** \ingroup solvers
  *  \brief Non-adaptive Euler solver
  */
 class EulerSolver: public GenericEulerSolver
 {
     STEPCORE_OBJECT(EulerSolver)
 public:
     EulerSolver(double stepSize = 0.01): GenericEulerSolver(stepSize, false) {}
     EulerSolver(int dimension, Function function, void* params, double stepSize)
                     : GenericEulerSolver(dimension, function, params, stepSize, false) {}
     EulerSolver(const EulerSolver& eulerSolver): GenericEulerSolver(eulerSolver) {}
 };
 
 /** \ingroup solvers
  *  \brief Adaptive Euler solver
  */
 class AdaptiveEulerSolver: public GenericEulerSolver
 {
     STEPCORE_OBJECT(AdaptiveEulerSolver)
 public:
     AdaptiveEulerSolver(): GenericEulerSolver(1, true) {}
     AdaptiveEulerSolver(int dimension, Function function, void* params)
                     : GenericEulerSolver(dimension, function, params, 1, true) {}
     AdaptiveEulerSolver(const AdaptiveEulerSolver& eulerSolver)
                     : GenericEulerSolver(eulerSolver) {}
 };
 
 } // namespace StepCore
 
 #endif