Rosenbrock34.H

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License
    This file is part of OpenFOAM.
 
    OpenFOAM 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 3 of the License, or
    (at your option) any later version.
 
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Class
    Foam::Rosenbrock34
 
Description
    L-stable embedded Rosenbrock ODE solver of order (3)4.
 
    \verbatim
        "Solving Ordinary Differential Equations II: Stiff
         and Differential-Algebraic Problems, second edition",
        Hairer, E.,
        Nørsett, S.,
        Wanner, G.,
        Springer-Verlag, Berlin. 1996.
    \endverbatim
 
    The default constants are from:
    \verbatim
        "Implementation of Rosenbrock Methods"
        Shampine, L. F.,
        ACM Transactions on Mathematical Software, vol. 8, 1982, pp. 93–113.
    \endverbatim
    with which the scheme is more accurate than with the L-Stable coefficients
    for small step-size but less stable for large step-size.
 
    The L-Stable scheme constants are provided commented-out in Rosenbrock34.C
 
SourceFiles
    Rosenbrock34.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef Rosenbrock34_H
#define Rosenbrock34_H
 
#include "ODESolver.H"
#include "adaptiveSolver.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                           Class Rosenbrock34 Declaration
\*---------------------------------------------------------------------------*/
 
class Rosenbrock34
:
    public ODESolver,
    public adaptiveSolver
{
    // Private data
 
        mutable scalarField k1_;
        mutable scalarField k2_;
        mutable scalarField k3_;
        mutable scalarField k4_;
        mutable scalarField err_;
        mutable scalarField dydx_;
        mutable scalarField dfdx_;
        mutable scalarSquareMatrix dfdy_;
        mutable scalarSquareMatrix a_;
        mutable labelList pivotIndices_;
 
        static const scalar
            a21, a31, a32,
            c21, c31, c32,
            c41, c42, c43,
            b1, b2, b3, b4,
            e1, e2, e3, e4,
            gamma,
            c2, c3,
            d1, d2, d3, d4;
 
 
public:
 
    //- Runtime type information
    TypeName("Rosenbrock34");
 
 
    // Constructors
 
        //- Construct from ODE
        Rosenbrock34(const ODESystem& ode, const dictionary& dict);
 
 
    // Member Functions
 
        //- Inherit solve from ODESolver
        using ODESolver::solve;
 
        //- Solve a single step dx and return the error
        scalar solve
        (
            const scalar x0,
            const scalarField& y0,
            const scalarField& dydx0,
            const scalar dx,
            scalarField& y
        ) const;
 
        //- Solve the ODE system and the update the state
        void solve
        (
            scalar& x,
            scalarField& y,
            scalar& dxTry
        ) const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //