110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration | Website: https://openfoam.org
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\\ / A nd | Copyright (C) 2018-2024 OpenFOAM Foundation
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\\/ M anipulation |
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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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\*---------------------------------------------------------------------------*/
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#include "randomGenerator.H"
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#include "PstreamReduceOps.H"
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// * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * * //
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Foam::scalar Foam::randomGenerator::scalarNormal()
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{
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// Proper inversion of the distribution. Slow. Exactly maintains
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// the random behaviour of the generator.
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/*
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using namespace constant::mathematical;
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static const scalar sqrtTwo = sqrt(scalar(2));
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static const scalar sqrtPiByTwo = sqrt(pi)/2;
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static const scalar a = 8*(pi - 3)/(3*pi*(4 - pi));
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const scalar x = 2*scalar01() - 1;
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const scalar xPos = mag(x);
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// Initial approximation
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const scalar l = log(1 - sqr(xPos));
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const scalar ll = 2/(pi*a) + l/2;
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scalar y = sqrt(sqrt(sqr(ll) - l/a) - ll);
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// Newton improvement
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label n = 0;
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while (n < 2)
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{
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const scalar dt = (erf(y) - xPos)/exp(- y*y)*sqrtPiByTwo;
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y -= dt;
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n += mag(dt) < rootSmall;
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}
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return sign(x)*sqrtTwo*y;
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*/
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// Box-Muller transform. Fast. Uses rejection and caching so the
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// random sequence is not guaranteed.
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if (scalarNormalStored_)
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{
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scalarNormalStored_ = false;
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return scalarNormalValue_;
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}
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else
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{
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scalar x1, x2, rr;
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do
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{
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x1 = 2*scalar01() - 1;
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x2 = 2*scalar01() - 1;
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rr = sqr(x1) + sqr(x2);
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}
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while (rr >= 1 || rr == 0);
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const scalar f = sqrt(- 2*log(rr)/rr);
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scalarNormalValue_ = x1*f;
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scalarNormalStored_ = true;
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return x2*f;
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}
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}
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Foam::scalar Foam::randomGenerator::globalScalar01()
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{
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scalar value = - vGreat;
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if (Pstream::master())
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{
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value = scalar01();
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}
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Pstream::scatter(value);
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return value;
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}
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// ************************************************************************* //
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