DILUPreconditioner.C

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    Copyright (C) 2019 OpenCFD Ltd.
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#include "DILUPreconditioner.H"
#include <algorithm>

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

namespace Foam
{
    defineTypeNameAndDebug(DILUPreconditioner, 0);

    lduMatrix::preconditioner::
        addasymMatrixConstructorToTable<DILUPreconditioner>
        addDILUPreconditionerAsymMatrixConstructorToTable_;
}


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

Foam::DILUPreconditioner::DILUPreconditioner
(
    const lduMatrix::solver& sol,
    const dictionary&
)
:
    lduMatrix::preconditioner(sol),
    rD_(sol.matrix().diag().size())
{
    const scalarField& diag = sol.matrix().diag();
    std::copy(diag.begin(), diag.end(), rD_.begin());

    calcReciprocalD(rD_, sol.matrix());
}


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

void Foam::DILUPreconditioner::calcReciprocalD
(
    solveScalarField& rD,
    const lduMatrix& matrix
)
{
    solveScalar* __restrict__ rDPtr = rD.begin();

    const label* const __restrict__ uPtr = matrix.lduAddr().upperAddr().begin();
    const label* const __restrict__ lPtr = matrix.lduAddr().lowerAddr().begin();

    const scalar* const __restrict__ upperPtr = matrix.upper().begin();
    const scalar* const __restrict__ lowerPtr = matrix.lower().begin();

    label nFaces = matrix.upper().size();
    for (label face=0; face<nFaces; face++)
    {
        rDPtr[uPtr[face]] -= upperPtr[face]*lowerPtr[face]/rDPtr[lPtr[face]];
    }


    // Calculate the reciprocal of the preconditioned diagonal
    const label nCells = rD.size();

    for (label cell=0; cell<nCells; cell++)
    {
        rDPtr[cell] = 1.0/rDPtr[cell];
    }
}


void Foam::DILUPreconditioner::precondition
(
    solveScalarField& wA,
    const solveScalarField& rA,
    const direction
) const
{
    solveScalar* __restrict__ wAPtr = wA.begin();
    const solveScalar* __restrict__ rAPtr = rA.begin();
    const solveScalar* __restrict__ rDPtr = rD_.begin();

    const label* const __restrict__ uPtr =
        solver_.matrix().lduAddr().upperAddr().begin();
    const label* const __restrict__ lPtr =
        solver_.matrix().lduAddr().lowerAddr().begin();

    const scalar* const __restrict__ upperPtr =
        solver_.matrix().upper().begin();
    const scalar* const __restrict__ lowerPtr =
        solver_.matrix().lower().begin();

    const label nCells = wA.size();
    const label nFaces = solver_.matrix().upper().size();
    const label nFacesM1 = nFaces - 1;

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

    for (label face=0; face<nFaces; face++)
    {
        wAPtr[uPtr[face]] -=
            rDPtr[uPtr[face]]*lowerPtr[face]*wAPtr[lPtr[face]];
    }

    for (label face=nFacesM1; face>=0; face--)
    {
        wAPtr[lPtr[face]] -=
            rDPtr[lPtr[face]]*upperPtr[face]*wAPtr[uPtr[face]];
    }
}


void Foam::DILUPreconditioner::preconditionT
(
    solveScalarField& wT,
    const solveScalarField& rT,
    const direction
) const
{
    solveScalar* __restrict__ wTPtr = wT.begin();
    const solveScalar* __restrict__ rTPtr = rT.begin();
    const solveScalar* __restrict__ rDPtr = rD_.begin();

    const label* const __restrict__ uPtr =
        solver_.matrix().lduAddr().upperAddr().begin();
    const label* const __restrict__ lPtr =
        solver_.matrix().lduAddr().lowerAddr().begin();
    const label* const __restrict__ losortPtr =
        solver_.matrix().lduAddr().losortAddr().begin();

    const scalar* const __restrict__ upperPtr =
        solver_.matrix().upper().begin();
    const scalar* const __restrict__ lowerPtr =
        solver_.matrix().lower().begin();

    const label nCells = wT.size();
    const label nFaces = solver_.matrix().upper().size();
    const label nFacesM1 = nFaces - 1;

    for (label cell=0; cell<nCells; cell++)
    {
        wTPtr[cell] = rDPtr[cell]*rTPtr[cell];
    }

    for (label face=0; face<nFaces; face++)
    {
        wTPtr[uPtr[face]] -=
            rDPtr[uPtr[face]]*upperPtr[face]*wTPtr[lPtr[face]];
    }


    for (label face=nFacesM1; face>=0; face--)
    {
        const label sface = losortPtr[face];
        wTPtr[lPtr[sface]] -=
            rDPtr[lPtr[sface]]*lowerPtr[sface]*wTPtr[uPtr[sface]];
    }
}


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