/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2016 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
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/>.

\*---------------------------------------------------------------------------*/

#include "PBiCGStab.H"

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
    defineTypeNameAndDebug(PBiCGStab, 0);

    lduMatrix::solver::addasymMatrixConstructorToTable<PBiCGStab>
        addPBiCGStabAsymMatrixConstructorToTable_;
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

Foam::PBiCGStab::PBiCGStab
(
    const word& fieldName,
    const lduMatrix& matrix,
    const FieldField<Field, scalar>& interfaceBouCoeffs,
    const FieldField<Field, scalar>& interfaceIntCoeffs,
    const lduInterfaceFieldPtrsList& interfaces,
    const dictionary& solverControls
)
:
    lduMatrix::solver
    (
        fieldName,
        matrix,
        interfaceBouCoeffs,
        interfaceIntCoeffs,
        interfaces,
        solverControls
    )
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

Foam::solverPerformance Foam::PBiCGStab::solve
(
    scalarField& psi,
    const scalarField& source,
    const direction cmpt
) const
{
    // --- Setup class containing solver performance data
    solverPerformance solverPerf
    (
        lduMatrix::preconditioner::getName(controlDict_) + typeName,
        fieldName_
    );

    const label nCells = psi.size();

    scalar* __restrict__ psiPtr = psi.begin();

    scalarField pA(nCells);
    scalar* __restrict__ pAPtr = pA.begin();

    scalarField yA(nCells);
    scalar* __restrict__ yAPtr = yA.begin();

    // --- Calculate A.psi
    matrix_.Amul(yA, psi, interfaceBouCoeffs_, interfaces_, cmpt);

    // --- Calculate initial residual field
    scalarField rA(source - yA);
    scalar* __restrict__ rAPtr = rA.begin();

    // --- Calculate normalisation factor
    const scalar normFactor = this->normFactor(psi, source, yA, pA);

    if (lduMatrix::debug >= 2)
    {
        Info<< "   Normalisation factor = " << normFactor << endl;
    }

    // --- Calculate normalised residual norm
    solverPerf.initialResidual() =
        gSumMag(rA, matrix().mesh().comm())
       /normFactor;
    solverPerf.finalResidual() = solverPerf.initialResidual();

    // --- Check convergence, solve if not converged
    if
    (
        minIter_ > 0
     || !solverPerf.checkConvergence(tolerance_, relTol_)
    )
    {
        scalarField AyA(nCells);
        scalar* __restrict__ AyAPtr = AyA.begin();

        scalarField sA(nCells);
        scalar* __restrict__ sAPtr = sA.begin();

        scalarField zA(nCells);
        scalar* __restrict__ zAPtr = zA.begin();

        scalarField tA(nCells);
        scalar* __restrict__ tAPtr = tA.begin();

        // --- Store initial residual
        const scalarField rA0(rA);

        // --- Initial values not used
        scalar rA0rA = 0;
        scalar alpha = 0;
        scalar omega = 0;

        // --- Select and construct the preconditioner
        autoPtr<lduMatrix::preconditioner> preconPtr =
        lduMatrix::preconditioner::New
        (
            *this,
            controlDict_
        );

        // --- Solver iteration
        do
        {
            // --- Store previous rA0rA
            const scalar rA0rAold = rA0rA;

            rA0rA = gSumProd(rA0, rA, matrix().mesh().comm());

            // --- Test for singularity
            if (solverPerf.checkSingularity(mag(rA0rA)))
            {
                break;
            }

            // --- Update pA
            if (solverPerf.nIterations() == 0)
            {
                for (label cell=0; cell<nCells; cell++)
                {
                    pAPtr[cell] = rAPtr[cell];
                }
            }
            else
            {
                // --- Test for singularity
                if (solverPerf.checkSingularity(mag(omega)))
                {
                    break;
                }

                const scalar beta = (rA0rA/rA0rAold)*(alpha/omega);

                for (label cell=0; cell<nCells; cell++)
                {
                    pAPtr[cell] =
                        rAPtr[cell] + beta*(pAPtr[cell] - omega*AyAPtr[cell]);
                }
            }

            // --- Precondition pA
            preconPtr->precondition(yA, pA, cmpt);

            // --- Calculate AyA
            matrix_.Amul(AyA, yA, interfaceBouCoeffs_, interfaces_, cmpt);

            const scalar rA0AyA = gSumProd(rA0, AyA, matrix().mesh().comm());

            alpha = rA0rA/rA0AyA;

            // --- Calculate sA
            for (label cell=0; cell<nCells; cell++)
            {
                sAPtr[cell] = rAPtr[cell] - alpha*AyAPtr[cell];
            }

            // --- Test sA for convergence
            solverPerf.finalResidual() =
                gSumMag(sA, matrix().mesh().comm())/normFactor;

            if (solverPerf.checkConvergence(tolerance_, relTol_))
            {
                for (label cell=0; cell<nCells; cell++)
                {
                    psiPtr[cell] += alpha*yAPtr[cell];
                }

                solverPerf.nIterations()++;

                return solverPerf;
            }

            // --- Precondition sA
            preconPtr->precondition(zA, sA, cmpt);

            // --- Calculate tA
            matrix_.Amul(tA, zA, interfaceBouCoeffs_, interfaces_, cmpt);

            const scalar tAtA = gSumSqr(tA, matrix().mesh().comm());

            // --- Calculate omega from tA and sA
            //     (cheaper than using zA with preconditioned tA)
            omega = gSumProd(tA, sA, matrix().mesh().comm())/tAtA;

            // --- Update solution and residual
            for (label cell=0; cell<nCells; cell++)
            {
                psiPtr[cell] += alpha*yAPtr[cell] + omega*zAPtr[cell];
                rAPtr[cell] = sAPtr[cell] - omega*tAPtr[cell];
            }

            solverPerf.finalResidual() =
                gSumMag(rA, matrix().mesh().comm())
               /normFactor;
        } while
        (
            (
                solverPerf.nIterations()++ < maxIter_
            && !solverPerf.checkConvergence(tolerance_, relTol_)
            )
         || solverPerf.nIterations() < minIter_
        );
    }

    return solverPerf;
}


// ************************************************************************* //