distribution.H

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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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    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
Class
    Foam::distribution
 
Description
    Base class for statistical distributions
 
    All distributions (except fixedValue) require a "size exponent", Q, to be
    specified along with their other coefficients. If a distribution's CDF(x)
    (cumulative distribution function) represents what proportion of the
    distribution takes a value below x, then Q determines what is meant by
    "proportion":
 
    - If Q=0, then "proportion" means the number of sampled values expected to
      be below x divided by the total number of sampled values.
 
    - If Q=3, then "proportion" means the expected sum of sampled values cubed
      for values below x divided by the total sum of values cubed. If x is a
      length, then this can be interpreted as a proportion of the total volume
      of sampled objects.
 
    - If Q=2, and x is a length, then the distribution might represent the
      proportion of surface area, and so on...
 
    In addition to the user-specification of Q defining what size the given
    distribution relates to, an implementation that uses a distribution can
    also programmatically define a samplingQ to determine what sort of sample
    is being constructed; whether the samples should have an equal number
    (sampleQ=0), volume (sampleQ=3), area (sampleQ=2), etc...
 
SourceFiles
    distribution.C
    distributionNew.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef distribution_H
#define distribution_H
 
#include "dictionary.H"
#include "Random.H"
#include "scalarField.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                        Class distribution Declaration
\*---------------------------------------------------------------------------*/
 
class distribution
{
protected:
 
    // Protected data
 
        //- Reference to a random number generator
        Random& rndGen_;
 
        //- Distribution size exponent
        const label Q_;
 
        //- Sample size exponent
        const label sampleQ_;
 
 
    // Protected Member Functions
 
        //- Validate that the bounds are monotonic
        virtual void validateBounds(const dictionary& dict) const;
 
        //- Validate that the lower bound is positive
        virtual void validatePositive(const dictionary& dict) const;
 
        //- Clip the PDF values to zero outside the bounds
        tmp<scalarField> clipPDF
        (
            const scalarField& x,
            const tmp<scalarField>& pdf
        ) const;
 
        //- Return the effective distribution size exponent
        inline label q() const
        {
            return sampleQ_ - Q_;
        }
 
 
public:
 
    //-Runtime type information
    TypeName("distribution");
 
 
    //- Declare runtime constructor selection table
    declareRunTimeSelectionTable
    (
        autoPtr,
        distribution,
        dictionary,
        (
            const dictionary& dict,
            Random& rndGen,
            const label sampleQ
        ),
        (dict, rndGen, sampleQ)
    );
 
 
    // Constructors
 
        //- Construct from dictionary
        distribution
        (
            const word& name,
            const dictionary& dict,
            Random& rndGen,
            const label sampleQ
        );
 
        //- Construct from components
        distribution(Random& rndGen, const label Q, const label sampleQ);
 
        //- Construct copy
        distribution(const distribution& d, const label sampleQ);
 
        //- Construct and return a clone
        virtual autoPtr<distribution> clone(const label sampleQ) const = 0;
 
        //- Construct and return a clone
        inline autoPtr<distribution> clone() const
        {
            return clone(sampleQ_);
        }
 
 
    //- Selector
    static autoPtr<distribution> New
    (
        const dictionary& dict,
        Random& rndGen,
        const label sampleQ
    );
 
 
    //- Destructor
    virtual ~distribution();
 
 
    // Member Functions
 
        //- Sample the distribution
        virtual scalar sample() const = 0;
 
        //- Sample the distribution
        virtual tmp<scalarField> sample(const label n) const = 0;
 
        //- Return the minimum value
        virtual scalar min() const = 0;
 
        //- Return the maximum value
        virtual scalar max() const = 0;
 
        //- Return the mean value
        virtual scalar mean() const = 0;
 
        //- Report
        void report() const;
 
        //- Return coordinates to plot across the range of the distribution
        virtual tmp<scalarField> x(const label n) const;
 
        //- Return the distribution probability density function
        virtual tmp<scalarField> PDF(const scalarField& x) const = 0;
};
 
 
/*---------------------------------------------------------------------------*\
                      Class FieldDistribution Declaration
\*---------------------------------------------------------------------------*/
 
template<class Base, class Derived>
class FieldDistribution
:
    public Base
{
public:
 
    // Constructors
 
        //- Inherit constructors
        using Base::Base;
 
 
    // Member Functions
 
        //- Sample the distribution
        using Base::sample;
 
        //- Sample the distribution
        virtual tmp<scalarField> sample(const label n) const
        {
            tmp<scalarField> tResult(new scalarField(n));
            scalarField& result = tResult.ref();
 
            forAll(result, i)
            {
                result[i] =
                    static_cast<const Derived&>(*this).sample();
            }
 
            return tResult;
        }
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //