exponential.C

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    Copyright (C) 2011-2016 OpenFOAM Foundation
    Copyright (C) 2021 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.
 
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    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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#include "exponential.H"
#include "addToRunTimeSelectionTable.H"
 
// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
namespace Foam
{
namespace distributionModels
{
    defineTypeNameAndDebug(exponential, 0);
    addToRunTimeSelectionTable(distributionModel, exponential, dictionary);
}
}
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
Foam::distributionModels::exponential::exponential
(
    const dictionary& dict,
    Random& rndGen
)
:
    distributionModel(typeName, dict, rndGen),
    lambda_(distributionModelDict_.get<scalar>("lambda"))
{
    if (lambda_ < VSMALL)
    {
        FatalErrorInFunction
            << "Rate parameter cannot be equal to or less than zero:" << nl
            << "    lambda = " << lambda_
            << exit(FatalError);
    }
 
    check();
}
 
 
Foam::distributionModels::exponential::exponential(const exponential& p)
:
    distributionModel(p),
    lambda_(p.lambda_)
{}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
Foam::scalar Foam::distributionModels::exponential::sample() const
{
    const scalar u = rndGen_.sample01<scalar>();
    const scalar qMin = exp(-lambda_*minValue_);
    const scalar qMax = exp(-lambda_*maxValue_);
    return -(scalar(1)/lambda_)*log(qMin + u*(qMax - qMin));
}
 
 
Foam::scalar Foam::distributionModels::exponential::meanValue() const
{
    return scalar(1)/lambda_;
}
 
 
// ************************************************************************* //