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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
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#include <algorithm>
namespace Gecode { namespace Support {
/** \brief Template for linear congruential generators
*
* This class template defines a simple class for linear
* congruential generators.
*
* \ingroup FuncSupport
*/
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
class LinearCongruentialGenerator {
private:
/// The maximum size of random numbers generated.
static constexpr unsigned int max_value = 1UL<<31;
/// Current seed value
unsigned int s;
/// Returns a random integer from the interval \f$[0\ldots n)\f$
unsigned int u(unsigned int n);
/// Returns a random integer from the interval \f$[0\ldots n)\f$
unsigned long long int ull(unsigned long long int n);
public:
/// Set the current seed to \a s
void seed(unsigned int s);
/// Construct the generator instance with seed \a s
LinearCongruentialGenerator(unsigned int s = 1);
/// Return current seed
unsigned int seed(void) const;
/// Generate next number in series
unsigned int next(void);
/// Returns a random integer from the interval \f$[0\ldots n)\f$
template<class Type>
Type operator ()(Type n);
/// Returns a random integer from the interval \f$[0\ldots n)\f$
int operator ()(int n);
/// Returns a random integer from the interval \f$[0\ldots n)\f$
unsigned int operator ()(unsigned int n);
/// Returns a random integer from the interval \f$[0\ldots n)\f$
long long int operator ()(long long int n);
/// Report size occupied
size_t size(void) const;
// Interface for conforming to C++ UniformRandomBitGenerator
/// Type of the produced values
typedef unsigned int result_type;
/// Minimum value that may be produced when no bound is specified
static constexpr result_type min() { return 0; }
/// Maximum value that may be produced when no bound is specified
static constexpr result_type max() { return max_value; }
/// Returns a random integer from the interval \f$[0\ldots max()]\f$
result_type operator()() { return next(); }
};
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>::u(unsigned int n) {
unsigned int x1 = next() & ((1U<<16)-1U);
unsigned int x2 = next() & ((1U<<16)-1U);
if (n < 2)
return 0;
double d = static_cast<double>(((x1<<16) | x2) % max_value) / max_value;
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 unsigned long long int
LinearCongruentialGenerator<m,a,q,r>::ull(unsigned long long int n) {
if (n <= UINT_MAX)
return u(static_cast<unsigned int>(n));
unsigned long long int x1 = next() & ((1LLU<<16)-1LLU);
unsigned long long int x2 = next() & ((1LLU<<16)-1LLU);
unsigned long long int x3 = next() & ((1LLU<<16)-1LLU);
unsigned long long int x4 = next() & ((1LLU<<16)-1LLU);
if (n < 2)
return 0;
return ((x1 << 48) | (x2 << 32) | (x3 << 16) | x4) % n;
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
template<class Type>
forceinline Type
LinearCongruentialGenerator<m,a,q,r>::operator ()(Type n) {
return static_cast<Type>(ull(static_cast<unsigned long long int>(n)));
}
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) {
return u(n);
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline int
LinearCongruentialGenerator<m,a,q,r>::operator ()(int n) {
return (n < 0) ? 0 :
static_cast<int>(u(static_cast<unsigned int>(n)));
}
template<unsigned int m, unsigned int a, unsigned int q, unsigned int r>
forceinline long long int
LinearCongruentialGenerator<m,a,q,r>::operator ()(long long int n) {
return (n < 0) ? 0 :
static_cast<long long int>
(ull(static_cast<unsigned long long int>(n)));
}
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>);
}
/** \brief Default values for linear congruential generator
*
* While this pseudo-random number generator is not a good source of
* randomness, it is still an acceptable choice for many
* applications. The choice of values is taken from D. E. Knuth,
* The Art of Computer Programming, Vol 2, Seminumerical Algorithms,
* 3rd edition.
*
* \ingroup FuncSupport
*/
typedef LinearCongruentialGenerator<2147483647, 48271, 44488, 3399>
RandomGenerator;
}}
// STATISTICS: support-any
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