182 lines
5.3 KiB
C++
182 lines
5.3 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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Class
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Foam::randomGenerator
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Description
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Random number generator
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This is a clone of the drand48 algorithm. This is significantly quicker
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than drand48, presumably due to the compiler inlining the sampling methods.
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It is also significantly quicker than the standard library linear
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congruential engine, as it does not use Schrage's algorithm to prevent
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overflow.
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See <http://pubs.opengroup.org/onlinepubs/007908775/xsh/drand48.html> for
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details of the seeding and iteration sequence.
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SourceFiles
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randomGenerator.C
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randomGeneratorI.H
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\*---------------------------------------------------------------------------*/
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#ifndef randomGenerator_H
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#define randomGenerator_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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Class randomGenerator Declaration
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\*---------------------------------------------------------------------------*/
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class randomGenerator
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{
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// Private Typedefs
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//- Working type
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typedef uint64_t type;
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// Private static data
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//- The parameters of the linear congruential iteration
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static const type A = 0x5DEECE66D, C = 0xB, M = type(1) << 48;
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// Private Data
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//- The stored integer
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type x_;
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//- Is a normal scalar sample stored?
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bool scalarNormalStored_;
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//- A stored normal scalar sample
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scalar scalarNormalValue_;
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// Private Member Functions
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//- Advance the state and return an integer sample
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inline type sample();
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public:
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// Constructors
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//- Construct from a seed
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inline randomGenerator(const label s);
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//- Destructor
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inline ~randomGenerator();
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// Member Functions
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// Scalars
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//- Advance the state and return a scalar sample from a uniform
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// distribution between zero and one
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inline scalar scalar01();
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//- Advance the state and return a scalar sample from a uniform
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// distribution between two limits
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inline scalar scalarAB(const scalar a, const scalar b);
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//- Advance the state and return a scalar sample from a normal
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// distribution with mean zero and standard deviation one
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scalar scalarNormal();
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// Other types
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//- Advance the state and return a sample of a given type from a
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// uniform distribution between zero and one
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template<class Type>
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inline Type sample01();
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//- Advance the state and return a sample of a given type from a
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// uniform distribution between two limits
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template<class Type>
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inline Type sampleAB(const Type& a, const Type& b);
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//- Advance the state and return a sample of a given type from a
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// normal distribution with mean zero and standard deviation one
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template<class Type>
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inline Type sampleNormal();
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// Global scalars
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//- Advance the state and return a scalar sample from a uniform
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// distribution between zero and one. Synchronises across all
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// cores. Use of this is discouraged. It is expensive and
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// introduces non-randomness in all cores other then the master.
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scalar globalScalar01();
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//- Randomly permute a list
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template<class Container>
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inline void permute(Container& l);
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};
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template<>
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inline scalar randomGenerator::sample01();
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template<>
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inline label randomGenerator::sample01();
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template<>
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inline scalar randomGenerator::sampleAB(const scalar& a, const scalar& b);
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template<>
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inline label randomGenerator::sampleAB(const label& a, const label& b);
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template<>
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inline scalar randomGenerator::sampleNormal();
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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} // End namespace Foam
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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#include "randomGeneratorI.H"
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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#endif
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// ************************************************************************* //
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