fieldStatistics.H

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/*---------------------------------------------------------------------------*\
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    Copyright (C) 2025 OpenCFD Ltd.
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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.
 
    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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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::functionObjects::fieldStatistics
 
Group
    grpFieldFunctionObjects
 
Description
    Calculates various statistics of the specified fields.
 
    Operands:
    \table
      Operand      | Type                  | Location
      input        | vol<Type>Field(s)     | Registry
      output file  | dat                   | postProcessing/<FO>/<time>/file
      output field | -                     | -
    \endtable
 
    where \c Type can be one of:
        \c Scalar, \c Vector, \c SphericalTensor, \c SymmTensor, or \c Tensor.
 
Usage
    Minimal example by using \c system/controlDict.functions:
    \verbatim
    fieldStatisticsFO
    {
        // Mandatory entries
        type             fieldStatistics;
        libs             (fieldFunctionObjects);
        fields           (<wordList>);
        statistics       (<wordList>);
 
        // Optional entries
        mode             <word>;
        mean             <word>;
        extrema          <bool>;
        internal         <bool>;
 
        // Inherited entries
        ...
    }
    \endverbatim
 
    where the entries mean:
    \table
      Property     | Description                        | Type | Reqd  | Deflt
      type         | Type name: fieldStatistics         | word | yes   | -
      libs         | Library name: fieldFunctionObjects | word | yes   | -
      fields       | List of operand fields             | wordList | yes | -
      statistics   | List of operand statistics         | wordList | yes | -
      mode   | Output format of the statistical results | word | no | magnitude
      mean     | Type of the mean operation             | word | no | arithmetic
      internal | Flag to use internal fields only in computing statistics <!--
               -->                                      | bool | no | false
      extrema | Flag to enable extrema data calculations | bool | no | false
    \endtable
 
    The inherited entries are elaborated in:
      - \link functionObject.H \endlink
      - \link writeFile.H \endlink
 
    Available statistics of the operand field through the \c statistics entry:
    \verbatim
      min        | Minimum value
      max        | Maximum value
      mean       | Arithmetic mean value (optionally volume-weighted)
      variance   | Sample variance value (unbiased)
    \endverbatim
 
    Options for the \c mode entry:
    \verbatim
      magnitude  | Output statistics magnitude-wise
      component  | Output statistics separately for each component
    \endverbatim
 
    Options for the \c mean entry:
    \verbatim
      arithmetic  | Arithmetic mean (average)
      volumetric  | Volume-weighted arithmetic mean
    \endverbatim
 
SourceFiles
    fieldStatistics.cxx
    fieldStatisticsImpl.cxx
 
\*---------------------------------------------------------------------------*/
 
#ifndef Foam_functionObjects_fieldStatistics_H
#define Foam_functionObjects_fieldStatistics_H
 
#include "fvMeshFunctionObject.H"
#include "writeFile.H"
#include "volFieldSelection.H"
#include <functional>
#include <variant>
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace functionObjects
{
 
/*---------------------------------------------------------------------------*\
                       Class fieldStatistics Declaration
\*---------------------------------------------------------------------------*/
 
class fieldStatistics
:
    public fvMeshFunctionObject,
    public writeFile
{
    // Private Enumerations
 
        //- Options for the output format of the statistical results
        enum class modeType : char
        {
            MAG = 0,    
            CMPT        
        };
 
        //- Names for modeType
        static const Enum<modeType> modeTypeNames_;
 
        //- Options for the mean type of the specified fields
        enum class meanType : char
        {
            ARITHMETIC = 0,  
            VOLUMETRIC       
        };
 
        //- Names for meanType
        static const Enum<meanType> meanTypeNames_;
 
        //- Options for the type of statistics calculation
        enum class calcType : char
        {
            UNKNOWN = 0,    
            MIN,            
            MAX,            
            MEAN,           
            VARIANCE        
        };
 
        //- Names for calcType
        static const Enum<calcType> calcTypeNames_;
 
 
    // Private Classes
 
        //- Type-safe union for input field types
        using variantInput = std::variant
        <
            scalarField,
            vectorField,
            sphericalTensorField,
            symmTensorField,
            tensorField
        >;
 
        //- Type-safe union for output data types
        using variantOutput = std::variant
        <
            scalar,
            vector,
            sphericalTensor,
            symmTensor,
            tensor
        >;
 
        //- Class to encapsulate information about specified statistic
        struct statistic
        {
            //- Name of the statistic
            word name_;
 
            //- Returns the value of the specified statistic
            std::function<variantOutput(variantInput)> calc;
        };
 
        //- Class to encapsulate the data about minima and maxima
        struct extremaData
        {
            //- Value of the extremum
            variantOutput value_;
 
            //- Processor index of the extremum
            label procID_;
 
            //- Cell index of the extremum
            label cellID_;
 
            //- Position (cell or face centre) of the extremum
            point position_;
        };
 
 
    // Private Data
 
        //- Flag to use internal fields only in computing statistics
        bool internal_;
 
        //- Flag to enable extrema data calculations
        bool extrema_;
 
        //- Output-format mode - only applicable for tensor ranks > 0
        modeType mode_;
 
        //- Type of the mean of the specified fields
        meanType mean_;
 
        //- Operand fields on which statistics are computed
        volFieldSelection fieldSet_;
 
        //- List of file pointers; one file per field
        HashPtrTable<OFstream> filePtrs_;
 
        //- List of file pointers for extrema data; one file per field
        HashPtrTable<OFstream> extremaFilePtrs_;
 
        //- Hash table containing all specified statistics
        HashTable<statistic> statistics_;
 
        //- Hash table containing all statistical results per field
        HashTable<HashTable<variantOutput>> results_;
 
        //- Hash table containing the results of the extrema per field
        HashTable<Pair<extremaData>> extremaResults_;
 
 
    // Private Member Functions
 
        //- Return the statistic container
        statistic createStatistic(const word& statName, const modeType mode);
 
        //- Compute the specified statistics of a given field
        template<class T>
        bool calcStat(const word& fieldName);
 
 
        // Central tendency statistics
 
        //- Return the arithmetic mean of the given input field
        template<class T>
        T calcMean(const Field<T>& field) const;
 
 
        // Dispersion statistics
 
        //- Return the minimum value of the given input field
        //  Store the processor index, cell index and location of the minimum
        template<class T>
        T calcMin(const Field<T>& field) const;
 
        //- Return the maximum value of the given input field
        //  Store the processor index, cell index and location of the maximum
        template<class T>
        T calcMax(const Field<T>& field) const;
 
        //- Return the sample variance of the given input field
        template<class T>
        T calcVariance(const Field<T>& field) const;
 
        //- Return a combined field: internal + flattened boundary
        template<class GeoField>
        tmp<Field<typename GeoField::value_type>>
        flatten(const GeoField& field) const;
 
        //- Return the extrema data of the specified field
        template<class GeoField>
        Pair<extremaData> calcExtremaData(const GeoField& field) const;
 
        //- Output the file header information
        void writeFileHeader(Ostream& os, const word& fieldName);
 
        //- Write the statistical data to the specified file
        void writeStatData();
 
        //- Write the statistical data to the standard stream
        void logStatData();
 
        //- Output the extrema-data file header information
        void writeExtremaFileHeader(Ostream& os, const word& fieldName);
 
        //- Write extrema data to the specified file
        void writeExtremaData();
 
        //- Write extrema data to the standard stream
        void logExtremaData();
 
 
public:
 
    //- Runtime type information
    TypeName("fieldStatistics");
 
 
    // Generated Methods
 
        //- No copy construct
        fieldStatistics(const fieldStatistics&) = delete;
 
        //- No copy assignment
        void operator=(const fieldStatistics&) = delete;
 
 
    // Constructors
 
        //- Construct from name, Time and dictionary
        fieldStatistics
        (
            const word& name,
            const Time& runTime,
            const dictionary& dict
        );
 
 
    //- Destructor
    virtual ~fieldStatistics() = default;
 
 
    // Member Functions
 
        //- Read the function-object dictionary
        virtual bool read(const dictionary& dict);
 
        //- Execute the function-object operations
        virtual bool execute();
 
        //- Write the function-object results
        virtual bool write();
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace functionObjects
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //