lineSearch.H

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-------------------------------------------------------------------------------
    Copyright (C) 2007-2023 PCOpt/NTUA
    Copyright (C) 2013-2023 FOSS GP
    Copyright (C) 2019 OpenCFD Ltd.
-------------------------------------------------------------------------------
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.
 
    OpenFOAM 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 General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
 
Class
    Foam::lineSearch
 
Description
    Abstract base class for line search methods
 
SourceFiles
    lineSearch.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef lineSearch_H
#define lineSearch_H
 
#include "runTimeSelectionTables.H"
#include "IOdictionary.H"
#include "scalarField.H"
#include "stepUpdate.H"
#include "updateMethod.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                          Class lineSearch Declaration
\*---------------------------------------------------------------------------*/
 
class lineSearch
{
protected:
 
    // Protected data
 
        //- Subdict within updateMethod
        const dictionary dict_;
 
        //- IOdictionary under time/uniform for continuation
        IOdictionary lineSearchDict_;
 
        //- Directional derivative of the merit function
        scalar directionalDeriv_;
 
        //- Update direction
        scalarField direction_;
 
        //- Old merit value from this opt cycle
        scalar oldMeritValue_;
 
        //- New merit value from this opt cycle
        scalar newMeritValue_;
 
        //- Merit directional deriv from the previous opt cycle
        scalar prevMeritDeriv_;
 
        //- Correction multiplier at the first step of line search
        scalar initialStep_;
 
        //- Minimum allowed correction multiplier
        scalar minStep_;
 
        //- Correction multiplier
        scalar step_;
 
        //- Optimisation cycle
        label iter_;
 
        //- Inner line search iteration
        label innerIter_;
 
        //- Maximum line search iterations
        label maxIters_;
 
        //- Whether to extrapolate the correction multiplier for
        //- this optimisation cycle based on the previous ones.
        //  Useful for non-quasi Newton methods
        bool extrapolateInitialStep_;
 
        //- Mechanism to update method if line search conditions are not set
        autoPtr<stepUpdate> stepUpdate_;
 
        //- Reference to the update method related to the line search
        updateMethod& updateMethod_;
 
 
    // Protected Member Functions
 
        //- Optional coeffs dict
        const dictionary& coeffsDict();
 
 
private:
 
    // Private Member Functions
 
        //- No copy construct
        lineSearch(const lineSearch&) = delete;
 
        //- No copy assignment
        void operator=(const lineSearch&) = delete;
 
 
public:
 
    //- Runtime type information
    TypeName("lineSearch");
 
 
    // Declare run-time constructor selection table
 
        declareRunTimeSelectionTable
        (
            autoPtr,
            lineSearch,
            dictionary,
            (
                const dictionary& dict,
                const Time& time,
                updateMethod& UpdateMethod
            ),
            (dict, time, UpdateMethod)
        );
 
 
    // Constructors
 
        //- Construct from components
        lineSearch
        (
            const dictionary& dict,
            const Time& time,
            updateMethod& UpdateMethod
        );
 
    // Selectors
 
        //- Return a reference to the selected turbulence model
        static autoPtr<lineSearch> New
        (
            const dictionary& dict,
            const Time& time,
            updateMethod& UpdateMethod
        );
 
 
    //- Destructor
    virtual ~lineSearch() = default;
 
 
    // Member Functions
 
        //- Set directional derivative
        virtual void setDeriv(const scalar deriv);
 
        //- Set new directional derivative.
        //  Does nothing in base. Only used by methods that require the
        //  gradient information to be computed at the new point
        virtual void setNewDeriv(const scalar deriv);
 
        //- Set direction
        inline void setDirection(const scalarField& direction)
        {
            direction_ = direction;
        }
 
        //- Set new objective value
        void setNewMeritValue(const scalar value);
 
        //- Set old objective value
        void setOldMeritValue(const scalar value);
 
        //- Reset step to initial value
        virtual void reset();
 
        //- Get inner line search iteration
        inline label innerIter() const
        {
            return innerIter_;
        }
 
        //- Get max number of iterations
        inline label maxIters() const
        {
            return maxIters_;
        }
 
        //- Get current step
        inline scalar step() const
        {
            return step_;
        }
 
        //- Return the correction of the design variables
        virtual bool converged() = 0;
 
        //- Update the line search step based on the specific line search
        //- strategy, e.g. bisection, quadratic fit, etc.
        virtual void updateStep() = 0;
 
        //- Update the step using the supplied value
        virtual void updateStep(const scalar newStep);
 
        //- Update the correction.
        //  Multiplies with step in base
        virtual void updateCorrection(scalarField& correction);
 
        //- Return true if lineSearch should continue and if so increment inner
        //  iteration
        virtual bool loop();
 
        //- Does line search need to update the gradient?
        virtual bool computeGradient() const;
 
        //- Execute steps at the end of the line search iterations
        virtual void postUpdate();
 
 
    // Member operators
 
        //- Increment iteration number and store merit value corresponding to
        //- the previous optimisation cycle
        virtual lineSearch& operator++();
 
        //- Postfix increment. Necessary for compilation
        virtual lineSearch& operator++(int);
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //