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https://develop.openfoam.com/Development/openfoam.git
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66d1b54a79
- centralises existing functions (erfInv, incGamma*, invIncGamma*). Provides a location for additional functions in the future. - adjusted existing models to use these functions (e.g. distributionModels::normal)
123 lines
4.2 KiB
C++
123 lines
4.2 KiB
C++
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration |
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\\ / A nd | www.openfoam.com
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\\/ M anipulation |
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-------------------------------------------------------------------------------
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Copyright (C) 2021 OpenCFD Ltd.
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-------------------------------------------------------------------------------
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License
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This file is part of OpenFOAM.
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OpenFOAM is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
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Namespace
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Foam::Math
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Description
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A namespace for various mathematical functions.
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Reference:
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\verbatim
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Inverse error function (tag:W):
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Winitzki, S. (2008).
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A handy approximation for the error function and its inverse.
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A lecture note obtained through private communication.
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URL:https://sites.google.com/site/winitzki/sergei-winitzkis-files
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(Retrieved on: 16 Feb 2021).
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Incomplete gamma functions (tag:DM):
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DiDonato, A. R., & Morris Jr, A. H. (1986).
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Computation of the incomplete gamma
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function ratios and their inverse.
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ACM Transactions on Mathematical Software (TOMS), 12(4), 377-393.
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DOI:10.1145/22721.23109
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\endverbatim
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Note
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- The algorithm in \c invIncGamma is described in (DM:Sec. 4).
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- The algorithm in \c incGammaRatio_Q is described in (DM:Sec. 3).
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- The accuracy parameter \c IND is set to a value of 1.
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SourceFiles
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erfInv.C
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incGamma.C
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invIncGamma.C
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\*---------------------------------------------------------------------------*/
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#ifndef MathFunctions_H
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#define MathFunctions_H
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#include "scalar.H"
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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namespace Foam
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{
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/*---------------------------------------------------------------------------*\
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Namespace Math Declaration
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\*---------------------------------------------------------------------------*/
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namespace Math
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{
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//- Inverse error function of a real-number argument
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// \param y Real-number argument at which to evaluate. Domain: (-1, 1)
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// \return The inverse of error function of y
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scalar erfInv(const scalar y);
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// Incomplete gamma functions
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//- Inverse of regularised lower incomplete gamma function
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// \param a Real-number argument. Domain: (0, infty]
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// \param P Real-number argument. Domain: [0,1]
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scalar invIncGamma(const scalar a, const scalar P);
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//- Regularised upper incomplete gamma function
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// \param a Real-number argument. Domain: (0, infty]
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// \param x Real-number argument. Domain: [0, infty]
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scalar incGammaRatio_Q(const scalar a, const scalar x);
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//- Regularised lower incomplete gamma function
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// \param a Real-number argument. Domain: (0, infty]
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// \param x Real-number argument. Domain: [0, infty]
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scalar incGammaRatio_P(const scalar a, const scalar x);
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//- Upper incomplete gamma function
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// \param a Real-number argument. Domain: (0, infty]
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// \param x Real-number argument. Domain: [0, infty]
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scalar incGamma_Q(const scalar a, const scalar x);
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//- Lower incomplete gamma function
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// \param a Real-number argument. Domain: (0, infty]
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// \param x Real-number argument. Domain: [0, infty]
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scalar incGamma_P(const scalar a, const scalar x);
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} // End namespace Math
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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} // End namespace Foam
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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#endif
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// ************************************************************************* //
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