PBiCG.C

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    Copyright (C) 2011-2017 OpenFOAM Foundation
    Copyright (C) 2019-2022 OpenCFD Ltd.
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License
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#include "PBiCG.H"
#include "PrecisionAdaptor.H"

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

namespace Foam
{
    defineTypeNameAndDebug(PBiCG, 0);

    lduMatrix::solver::addasymMatrixConstructorToTable<PBiCG>
        addPBiCGAsymMatrixConstructorToTable_;
}


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

Foam::PBiCG::PBiCG
(
    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::PBiCG::solve
(
    scalarField& psi_s,
    const scalarField& source,
    const direction cmpt
) const
{
    PrecisionAdaptor<solveScalar, scalar> tpsi(psi_s);
    solveScalarField& psi = tpsi.ref();

    // --- Setup class containing solver performance data
    solverPerformance solverPerf
    (
        lduMatrix::preconditioner::getName(controlDict_) + typeName,
        fieldName_
    );

    const 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();

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

    // --- Calculate initial residual field
    ConstPrecisionAdaptor<solveScalar, scalar> tsource(source);
    solveScalarField rA(tsource() - wA);
    solveScalar* __restrict__ rAPtr = rA.begin();

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

    // --- Calculate normalisation factor
    const solveScalar normFactor = this->normFactor(psi, tsource(), 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_)
    )
    {
        solveScalarField pT(nCells, 0);
        solveScalar* __restrict__ pTPtr = pT.begin();

        solveScalarField wT(nCells);
        solveScalar* __restrict__ wTPtr = wT.begin();

        // --- Calculate T.psi
        matrix_.Tmul(wT, psi, interfaceIntCoeffs_, interfaces_, cmpt);

        // --- Calculate initial transpose residual field
        solveScalarField rT(tsource() - wT);
        solveScalar* __restrict__ rTPtr = rT.begin();

        // --- Initial value not used
        solveScalar wArT = 0;

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

        // --- Solver iteration
        do
        {
            // --- Store previous wArT
            const solveScalar wArTold = wArT;

            // --- Precondition residuals
            preconPtr_->precondition(wA, rA, cmpt);
            preconPtr_->preconditionT(wT, rT, cmpt);

            // --- Update search directions:
            wArT = gSumProd(wA, rT, matrix().mesh().comm());

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

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


            // --- Update preconditioned residuals
            matrix_.Amul(wA, pA, interfaceBouCoeffs_, interfaces_, cmpt);
            matrix_.Tmul(wT, pT, interfaceIntCoeffs_, interfaces_, cmpt);

            const solveScalar wApT = gSumProd(wA, pT, matrix().mesh().comm());

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


            // --- Update solution and residual:

            const solveScalar alpha = wArT/wApT;

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

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

    // Recommend PBiCGStab if PBiCG fails to converge
    const label upperMaxIters = max(maxIter_, lduMatrix::defaultMaxIter);

    if (solverPerf.nIterations() > upperMaxIters)
    {
        FatalErrorInFunction
            << "PBiCG has failed to converge within the maximum iterations: "
            << upperMaxIters << nl
            << "    Please try the more robust PBiCGStab solver."
            << exit(FatalError);
    }

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

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

    return solverPerf;
}


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