random.hpp
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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
* Main authors:
* Christian Schulte <schulte@gecode.org>
* Mikael Lagerkvist <lagerkvist@gecode.org>
*
* Copyright:
* Christian Schulte, 2005
* Mikael Lagerkvist, 2005
*
* This file is part of Gecode, the generic constraint
* development environment:
* http://www.gecode.org
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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namespace Gecode { namespace Support {
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
class LinearCongruentialGenerator {
private:
static const unsigned int max = 1UL<<31;
unsigned int s;
unsigned int next(void);
public:
void seed(unsigned int s);
LinearCongruentialGenerator(unsigned int s = 1);
unsigned int seed(void) const;
unsigned int operator ()(unsigned int n);
size_t size(void) const;
};
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline unsigned int
LinearCongruentialGenerator<m,a,q,r>::next(void) {
s = a*(s%q) - r*(s/q);
unsigned int res = s;
if (s==0) s = 1;
return res;
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline void
LinearCongruentialGenerator<m,a,q,r>::seed(unsigned int _s) {
s = _s % m;
if (s == 0) s = 1;
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline
LinearCongruentialGenerator<m,a,q,r>::
LinearCongruentialGenerator(unsigned int _s) {
seed(_s);
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline unsigned int
LinearCongruentialGenerator<m,a,q,r>::seed(void) const {
return s;
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline unsigned int
LinearCongruentialGenerator<m,a,q,r>::operator ()(unsigned int n) {
unsigned int x1 = next() & ((1<<16)-1);
unsigned int x2 = next() & ((1<<16)-1);
if (n < 2) return 0;
double d = static_cast<double>(((x1<<16) | x2) % max) / max;
unsigned int val = static_cast<unsigned int>(n * d);
return (val < n) ? val : (n-1);
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline size_t
LinearCongruentialGenerator<m,a,q,r>::size(void) const {
return sizeof(LinearCongruentialGenerator<m,a,q,r>);
}
typedef LinearCongruentialGenerator<2147483647, 48271, 44488, 3399>
RandomGenerator;
}}
// STATISTICS: support-any
Gecode::Support::LinearCongruentialGenerator
Template for linear congruential generators.
Definition random.hpp:46
Gecode::Support::LinearCongruentialGenerator::size
size_t size(void) const
Report size occupied.
Definition random.hpp:104
Gecode::Support::LinearCongruentialGenerator::operator()
unsigned int operator()(unsigned int n)
Returns a random integer from the interval [0..n).
Definition random.hpp:94
Gecode::Support::LinearCongruentialGenerator::LinearCongruentialGenerator
LinearCongruentialGenerator(unsigned int s=1)
Construct the generator instance with seed s.
Definition random.hpp:84
Gecode::Support::LinearCongruentialGenerator::seed
void seed(unsigned int s)
Set the current seed to s.
Definition random.hpp:77
Gecode::Support::LinearCongruentialGenerator::seed
unsigned int seed(void) const
Return current seed.
Definition random.hpp:89
Gecode::Support::RandomGenerator
LinearCongruentialGenerator< 2147483647, 48271, 44488, 3399 > RandomGenerator
Default values for linear congruential generator.
Definition random.hpp:120
Gecode::Support
Support algorithms and datastructures
Gecode
Gecode toplevel namespace
forceinline
#define forceinline
Definition config.hpp:187