unintegrable.C

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#include "unintegrable.H"
#include "quadraticEqn.H"
#include "SubField.H"
#include "addToRunTimeSelectionTable.H"
 
// * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
Foam::tmp<Foam::scalarField> Foam::distributions::unintegrable::integrate
(
    const scalarField& x,
    const scalarField& y
)
{
    tmp<scalarField> tResult(new scalarField(x.size()));
    scalarField& result = tResult.ref();
 
    result[0] = 0;
 
    for (label i = 1; i < x.size(); ++ i)
    {
        result[i] = result[i - 1] + (x[i] - x[i - 1])*(y[i] + y[i - 1])/2;
    }
 
    return tResult;
}
 
 
Foam::tmp<Foam::scalarField> Foam::distributions::unintegrable::integrateX
(
    const scalarField& x,
    const scalarField& y
)
{
    tmp<scalarField> tResult(new scalarField(x.size()));
    scalarField& result = tResult.ref();
 
    result[0] = 0;
 
    for (label i = 1; i < x.size(); ++ i)
    {
        const scalar x0 = x[i - 1], x1 = x[i];
        const scalar y0 = y[i - 1], y1 = y[i];
 
        result[i] =
            result[i - 1] + (x1 - x0)*(2*x0*y0 + x0*y1 + x1*y0 + 2*x1*y1)/6;
    }
 
    return tResult;
}
 
 
Foam::scalar Foam::distributions::unintegrable::sampleInterval
(
    const Pair<scalar>& x,
    const Pair<scalar>& Phi,
    const scalar s
)
{
    // Do a linear interpolation
    scalar f = (s - Phi[0])/(Phi[1] - Phi[0]);
 
    // Interpolate
    return (1 - f)*x[0] + f*x[1];
}
 
 
Foam::scalar Foam::distributions::unintegrable::sampleInterval
(
    const Pair<scalar>& x,
    const Pair<scalar>& phi,
    const Pair<scalar>& Phi,
    const scalar s
)
{
    // Do a linear interpolation
    scalar f = (s - Phi[0])/(Phi[1] - Phi[0]);
 
    // Attempt to improve by doing a quadratic interpolation
    const scalar a = (x[1] - x[0])*(phi[1] - phi[0])/2;
    const scalar b = Phi[1] - Phi[0] - a;
    const scalar c = Phi[0] - s;
    const quadraticEqn eqn(a, b, c);
    const Roots<2> roots = eqn.roots();
    forAll(roots, rooti)
    {
        if
        (
            roots.type(rooti) == rootType::real
         && roots[rooti] > 0
         && roots[rooti] < 1
        )
        {
            f = roots[rooti];
        }
    }
 
    // Interpolate
    return (1 - f)*x[0] + f*x[1];
}
 
 
Foam::scalar Foam::distributions::unintegrable::sample
(
    const scalarField& x,
    const scalarField& Phi,
    const scalar s
)
{
    // Find the interval
    label i = 0;
    for (; i < x.size() && Phi[i + 1] < s; ++ i);
 
    // Sample
    return
        sampleInterval
        (
            {x[i], x[i + 1]},
            {Phi[i], Phi[i + 1]},
            s
        );
}
 
 
Foam::scalar Foam::distributions::unintegrable::sample
(
    const scalarField& x,
    const scalarField& phi,
    const scalarField& Phi,
    const scalar s
)
{
    // Find the interval
    label i = 0;
    for (; i < x.size() && Phi[i + 1] < s; ++ i);
 
    // Sample
    return
        sampleInterval
        (
            {x[i], x[i + 1]},
            {phi[i], phi[i + 1]},
            {Phi[i], Phi[i + 1]},
            s
        );
}
 
 
// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
const Foam::scalarField& Foam::distributions::unintegrable::x() const
{
    if (xPtr_.valid()) return xPtr_();
 
    xPtr_.set(new scalarField(n_));
    scalarField& x = xPtr_();
 
    forAll(x, i)
    {
        const scalar f = scalar(i)/(n_ + 1);
        x[i] = (1 - f)*this->min() + f*this->max();
    }
 
    static const scalar tol = sqrt(sqrt(pow3(small)));
 
    for (label iter = 0; iter < ceil(std::log2(1/tol)); ++ iter)
    {
        const scalarField phi(this->phi(this->q(), x));
        const scalarField Phi(integrate(x, phi));
 
        const scalar dPhi = (Phi.last() - Phi.first())/(n_ - 1);
 
        if (distribution::debug)
        {
            scalar error = -vGreat;
            for (label i = 0; i < n_ - 1; ++ i)
            {
                error = Foam::max(error, (1 - (Phi[i + 1] - Phi[i])/dPhi)/n_);
            }
 
            Info<< indent << "Interval spacing iteration #" << iter
                << ", error=" << error << endl;
        }
 
        const scalarField xPrev(x);
 
        x.first() = this->min();
 
        for (label i0 = 0, i = 1; i0 < n_ - 1; ++ i0)
        {
            while (Phi[i0 + 1] > i*dPhi)
            {
                const scalar xNext =
                    sampleInterval
                    (
                        {xPrev[i0], xPrev[i0 + 1]},
                        {phi[i0], phi[i0 + 1]},
                        {Phi[i0], Phi[i0 + 1]},
                        i*dPhi
                    );
 
                x[i] = (x[i] + xNext)/2;
 
                i ++;
            }
        }
 
        x.last() = this->max();
    }
 
    return x;
}
 
const Foam::scalarField& Foam::distributions::unintegrable::PDF() const
{
    if (PDFPtr_.valid()) return PDFPtr_();
 
    const Pair<scalar> Phi01 = this->Phi01();
 
    PDFPtr_.set((phi(this->q(), xPtr_)/(Phi01[1] - Phi01[0])).ptr());
 
    return PDFPtr_();
}
 
 
// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
 
Foam::tmp<Foam::scalarField> Foam::distributions::unintegrable::Phi
(
    const label q,
    const scalarField& x
) const
{
    return integrate(x, phi(q, x));
}
 
 
Foam::Pair<Foam::scalar> Foam::distributions::unintegrable::Phi01
(
    const label q
) const
{
    const scalarField Phi(this->Phi(this->q(), x()));
 
    return Pair<scalar>(Phi.first(), Phi.last());
}
 
 
Foam::Pair<Foam::scalar> Foam::distributions::unintegrableForNonZeroQ::Phi01
(
    const label q
) const
{
    if (q == 0)
    {
        const scalarField x(scalarList({min(), max()}));
        const scalarField Phi(this->Phi(q, x));
        return Pair<scalar>(Phi.first(), Phi.last());
    }
    else
    {
        return unintegrable::Phi01(q);
    }
}
 
 
const Foam::Pair<Foam::scalar>&
Foam::distributions::unintegrable::Phi01() const
{
    if (Phi01Ptr_.valid()) return Phi01Ptr_();
 
    Phi01Ptr_.set(new Pair<scalar>(Phi01(this->q())));
 
    return Phi01Ptr_();
}
 
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
Foam::distributions::unintegrable::unintegrable
(
    const word& name,
    const dictionary& dict,
    Random& rndGen,
    const label sampleQ
)
:
    distribution(name, dict, rndGen, sampleQ),
    n_((1<<dict.lookupOrDefault<label>("level", 16)) + 1)
{}
 
 
Foam::distributions::unintegrable::unintegrable
(
    Random& rndGen,
    const label Q,
    const label sampleQ,
    const label n
)
:
    distribution(rndGen, Q, sampleQ),
    n_(n)
{}
 
 
Foam::distributions::unintegrable::unintegrable
(
    const unintegrable& d,
    const label sampleQ
)
:
    distribution(d, sampleQ),
    n_(d.n_)
{}
 
 
// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
Foam::distributions::unintegrable::~unintegrable()
{}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
Foam::scalar Foam::distributions::unintegrable::sample() const
{
    const scalar s = this->rndGen_.template sample01<scalar>();
 
    const scalar dCDF = scalar(1)/(n_ - 1);
    const label samplei = floor(s/dCDF);
    return
        sampleInterval
        (
            {x()[samplei], x()[samplei + 1]},
            {PDF()[samplei], PDF()[samplei + 1]},
            {samplei*dCDF, (samplei + 1)*dCDF},
            s
        );
}
 
 
Foam::scalar Foam::distributions::unintegrable::mean() const
{
    const Pair<scalar> Phi01 = this->Phi01();
    const scalarField Mu(Phi(this->q() + 1, x()));
    const Pair<scalar> Mu01(Mu.first(), Mu.last());
    return (Mu01[1] - Mu01[0])/(Phi01[1] - Phi01[0]);
}
 
 
Foam::tmp<Foam::scalarField> Foam::distributions::unintegrable::PDF
(
    const scalarField& x
) const
{
    const scalarField phi(this->phi(this->q(), x));
    const Pair<scalar> Phi01 = this->Phi01();
    return this->clipPDF(x, phi/(Phi01[1] - Phi01[0]));
}
 
 
// ************************************************************************* //