FPCG.C

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/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
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     \\/     M anipulation  |
-------------------------------------------------------------------------------
    Copyright (C) 2011-2017 OpenFOAM Foundation
    Copyright (C) 2019-2021 OpenCFD Ltd.
    Copyright (C) 2023 Huawei (Yu Ankun)
-------------------------------------------------------------------------------
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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    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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#include "FPCG.H"
#include "PrecisionAdaptor.H"

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

namespace Foam
{
    defineTypeNameAndDebug(FPCG, 0);

    lduMatrix::solver::addsymMatrixConstructorToTable<FPCG>
        addFPCGSymMatrixConstructorToTable_;
}


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

Foam::FPCG::FPCG
(
    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
    )
{}


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

void Foam::FPCG::gSumMagProd
(
    FixedList<solveScalar, 2>& globalSum,
    const solveScalarField& a,
    const solveScalarField& b,
    const label comm
)
{
    const label nCells = a.size();

    globalSum = 0.0;
    for (label cell=0; cell<nCells; ++cell)
    {
        globalSum[0] += a[cell]*b[cell];    // sumProd(a, b)
        globalSum[1] += mag(b[cell]);       // sumMag(b)
    }

    Foam::reduce
    (
        globalSum.data(),
        globalSum.size(),
        sumOp<solveScalar>(),
        UPstream::msgType(),  // (ignored): direct MPI call
        comm
    );
}

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

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

    label nCells = psi.size();

    solveScalar* __restrict__ psiPtr = psi.begin();

    solveScalarField pA(nCells);
    solveScalar* __restrict__ pAPtr = pA.begin();

    solveScalarField wA(nCells);
    solveScalar* __restrict__ wAPtr = wA.begin();

    solveScalar wArA = solverPerf.great_;
    solveScalar wArAold = wArA;

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

    // --- Calculate initial residual field
    solveScalarField rA(source - wA);
    solveScalar* __restrict__ rAPtr = rA.begin();

    matrix().setResidualField
    (
        ConstPrecisionAdaptor<scalar, solveScalar>(rA)(),
        fieldName_,
        true
    );

    // --- Calculate normalisation factor
    solveScalar normFactor = this->normFactor(psi, source, wA, pA);

    if ((log_ >= 2) || (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_, log_)
    )
    {
        // --- Select and construct the preconditioner
        if (!preconPtr_)
        {
            preconPtr_ = lduMatrix::preconditioner::New
            (
                *this,
                controlDict_
            );
        }

        FixedList<solveScalar, 2> globalSum;

        // --- Solver iteration
        do
        {
            // --- Store previous wArA
            wArAold = wArA;

            // --- Precondition residual
            preconPtr_->precondition(wA, rA, cmpt);

            // --- Update search directions and calculate residual:
            gSumMagProd(globalSum, wA, rA, matrix().mesh().comm());

            wArA = globalSum[0];

            solverPerf.finalResidual() = globalSum[1]/normFactor;

            // Check convergence (bypass if not enough iterations yet)
            if
            (
                (minIter_ <= 0 || solverPerf.nIterations() >= minIter_)
             && solverPerf.checkConvergence(tolerance_, relTol_, log_)
            )
            {
                break;
            }

            if (solverPerf.nIterations() == 0)
            {
                for (label cell=0; cell<nCells; cell++)
                {
                    pAPtr[cell] = wAPtr[cell];
                }
            }
            else
            {
                const solveScalar beta = wArA/wArAold;

                for (label cell=0; cell<nCells; cell++)
                {
                    pAPtr[cell] = wAPtr[cell] + beta*pAPtr[cell];
                }
            }


            // --- Update preconditioned residual
            matrix_.Amul(wA, pA, interfaceBouCoeffs_, interfaces_, cmpt);

            solveScalar wApA = gSumProd(wA, pA, matrix().mesh().comm());

            // --- Test for singularity
            if (solverPerf.checkSingularity(mag(wApA)/normFactor)) break;


            // --- Update solution and residual:

            const solveScalar alpha = wArA/wApA;

            for (label cell=0; cell<nCells; cell++)
            {
                psiPtr[cell] += alpha*pAPtr[cell];
                rAPtr[cell] -= alpha*wAPtr[cell];
            }

        } while
        (
            ++solverPerf.nIterations() < maxIter_
        );
    }

    if (preconPtr_)
    {
        preconPtr_->setFinished(solverPerf);
    }

    matrix().setResidualField
    (
        ConstPrecisionAdaptor<scalar, solveScalar>(rA)(),
        fieldName_,
        false
    );

    return solverPerf;
}



Foam::solverPerformance Foam::FPCG::solve
(
    scalarField& psi_s,
    const scalarField& source,
    const direction cmpt
) const
{
    PrecisionAdaptor<solveScalar, scalar> tpsi(psi_s);
    return scalarSolve
    (
        tpsi.ref(),
        ConstPrecisionAdaptor<solveScalar, scalar>(source)(),
        cmpt
    );
}


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