//
// diis.h
//
// Copyright (C) 1996 Limit Point Systems, Inc.
//
// Author: Curtis Janssen <cljanss@limitpt.com>
// Maintainer: LPS
//
// This file is part of the SC Toolkit.
//
// The SC Toolkit is free software; you can redistribute it and/or modify
// it under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// The SC Toolkit 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 Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with the SC Toolkit; see the file COPYING.LIB.  If not, write to
// the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
//
// The U.S. Government is granted a limited license as per AL 91-7.
//

#ifndef _math_optimize_diis_h
#define _math_optimize_diis_h

#ifdef __GNUC__
#pragma interface
#endif

#include <math/optimize/scextrap.h>

namespace sc {

/** The DIIS class provides DIIS extrapolation. */
class DIIS: public SelfConsistentExtrapolation {
  protected:
    int start;
    int ndiis;
    int iter;
    int ngroup;
    int ngroupdiis;
    double damping_factor;

    double * btemp;
    double ** bold;
    double ** bmat;

    Ref<SCExtrapData> dtemp_data;
    Ref<SCExtrapError> dtemp_error;

    Ref<SCExtrapData> Ldata;

    Ref<SCExtrapData> *diism_data;
    Ref<SCExtrapError> *diism_error;

    void init();
  public:
    DIIS(int strt=1, int ndi=5, double dmp =0, int ngr=1, int ngrdiis=1);
    DIIS(StateIn&);
    /** The DIIS KeyVal constructor recognizes the following keywords:

        <dl>

        <dt><tt>n</tt><dd> This integer maximum number of data sets to
        retain.  The default is 5.

        <dt><tt>start</tt><dd> The DIIS extrapolation will begin on the
        iteration given by this integer.  The default is 1.

        <dt><tt>damping_factor</tt><dd> This nonnegative floating point
        number is used to dampen the DIIS extrapolation.  The default is
        0.0.

        <dt><tt>ngroup</tt><dd> The number of iterations in a DIIS group.
        DIIS extrapolation is only used for the first ngroupdiis of these
        interations.  The default is 1.  If ngroup is 1 and ngroupdiis is
        greater than 0, then DIIS will be used on all iterations after and
        including the start iteration.

        <dt><tt>ngroupdiis</tt><dd> The number of DIIS extrapolations to do
        at the beginning of an iteration group.  See the documentation for
        ngroup.

        </dl> */
    DIIS(const Ref<KeyVal>&);
    ~DIIS();

    void save_data_state(StateOut&);
    
    int extrapolate(const Ref<SCExtrapData>& data,
                    const Ref<SCExtrapError>& error);

    void start_extrapolation();

    void reinitialize();

    /// Override DescribedClass::print.
    void print(std::ostream& = ExEnv::out0()) const;
};

}

#endif

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