/usr/include/boost/random
Edit: /usr/include/boost/random/seed_seq.hpp (3792B)
/* boost random/seed_seq.hpp header file
*
* Copyright Steven Watanabe 2010
* Distributed under the Boost Software License, Version 1.0. (See
* accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org for most recent version including documentation.
*
* $Id$
*
*/
#ifndef BOOST_RANDOM_SEED_SEQ_HPP
#define BOOST_RANDOM_SEED_SEQ_HPP
#include
#include
#include
#include
#include
#include
#include
#include
#ifndef BOOST_NO_CXX11_HDR_INITIALIZER_LIST
#include
#endif
namespace boost {
namespace random {
/**
* The class @c seed_seq stores a sequence of 32-bit words
* for seeding a \pseudo_random_number_generator. These
* words will be combined to fill the entire state of the
* generator.
*/
class seed_seq {
public:
typedef boost::uint_least32_t result_type;
/** Initializes a seed_seq to hold an empty sequence. */
seed_seq() {}
#ifndef BOOST_NO_CXX11_HDR_INITIALIZER_LIST
/** Initializes the sequence from an initializer_list. */
template
seed_seq(const std::initializer_list& il) : v(il.begin(), il.end()) {}
#endif
/** Initializes the sequence from an iterator range. */
template
seed_seq(Iter first, Iter last) : v(first, last) {}
/** Initializes the sequence from Boost.Range range. */
template
explicit seed_seq(const Range& range)
: v(boost::begin(range), boost::end(range)) {}
/**
* Fills a range with 32-bit values based on the stored sequence.
*
* Requires: Iter must be a Random Access Iterator whose value type
* is an unsigned integral type at least 32 bits wide.
*/
template
void generate(Iter first, Iter last) const
{
typedef typename std::iterator_traits::value_type value_type;
std::fill(first, last, static_cast(0x8b8b8b8bu));
std::size_t s = v.size();
std::size_t n = last - first;
std::size_t t =
(n >= 623) ? 11 :
(n >= 68) ? 7 :
(n >= 39) ? 5 :
(n >= 7) ? 3 :
(n - 1)/2;
std::size_t p = (n - t) / 2;
std::size_t q = p + t;
std::size_t m = (std::max)(s+1, n);
value_type mask = 0xffffffffu;
for(std::size_t k = 0; k < m; ++k) {
value_type r1 = static_cast
(*(first + k%n) ^ *(first + (k+p)%n) ^ *(first + (k+n-1)%n));
r1 = r1 ^ (r1 >> 27);
r1 = (r1 * 1664525u) & mask;
value_type r2 = static_cast(r1 +
((k == 0) ? s :
(k <= s) ? k % n + v[k - 1] :
(k % n)));
*(first + (k+p)%n) = (*(first + (k+p)%n) + r1) & mask;
*(first + (k+q)%n) = (*(first + (k+q)%n) + r2) & mask;
*(first + k%n) = r2;
}
for(std::size_t k = m; k < m + n; ++k) {
value_type r3 = static_cast
((*(first + k%n) + *(first + (k+p)%n) + *(first + (k+n-1)%n))
& mask);
r3 = r3 ^ (r3 >> 27);
r3 = (r3 * 1566083941u) & mask;
value_type r4 = static_cast(r3 - k%n);
*(first + (k+p)%n) ^= r3;
*(first + (k+q)%n) ^= r4;
*(first + k%n) = r4;
}
}
/** Returns the size of the sequence. */
std::size_t size() const { return v.size(); }
/** Writes the stored sequence to iter. */
template
void param(Iter out) { std::copy(v.begin(), v.end(), out); }
private:
std::vector v;
};
}
}
#endif