// Wild Magic Source Code
// David Eberly
// http://www.geometrictools.com
// Copyright (c) 1998-2008
//
// This library 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 2.1 of the License, or (at
// your option) any later version.  The license is available for reading at
// either of the locations:
//     http://www.gnu.org/copyleft/lgpl.html
//     http://www.geometrictools.com/License/WildMagicLicense.pdf
//
// Version: 4.0.0 (2006/06/28)

#ifndef WM4ODEIMPLICITEULER_H
#define WM4ODEIMPLICITEULER_H

#include "Wm4FoundationLIB.h"
#include "Wm4OdeSolver.h"
#include "Wm4GMatrix.h"

namespace Wm4
{

template <class Real>
class WM4_FOUNDATION_ITEM OdeImplicitEuler : public OdeSolver<Real>
{
public:
    // The function F(t,x) has input t, a scalar, and input x, an n-vector.
    // The first derivative matrix with respect to x is DF(t,x), an
    // n-by-n matrix.  Entry DF[r][c] is the derivative of F[r] with
    // respect to x[c].
    typedef void (*DerivativeFunction)(
        Real,             // t
        const Real*,      // x
        void*,            // user-specified data
        GMatrix<Real>&);  // DF(t,x)

    OdeImplicitEuler (int iDim, Real fStep,
        typename OdeSolver<Real>::Function oFunction,
        DerivativeFunction oDFunction, void* pvData = 0);

    virtual ~OdeImplicitEuler ();

    virtual void Update (Real fTIn, Real* afXIn, Real& rfTOut,
        Real* afXOut);

    virtual void SetStepSize (Real fStep);

protected:
    using OdeSolver<Real>::m_iDim;
    using OdeSolver<Real>::m_fStep;
    using OdeSolver<Real>::m_pvData;

    DerivativeFunction m_oDFunction;
    GMatrix<Real> m_kDF;
    GVector<Real> m_kF;
    GMatrix<Real> m_kIdentity;
};

typedef OdeImplicitEuler<float> OdeImplicitEulerf;
typedef OdeImplicitEuler<double> OdeImplicitEulerd;

}

#endif
