82 lines
2.0 KiB
C++
82 lines
2.0 KiB
C++
/*
|
|
* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
*
|
|
* Copyright 2015-2019 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#include "xorshift.hpp"
|
|
|
|
#include "../debug.hpp"
|
|
|
|
#include <cstdint>
|
|
|
|
using cruft::rand::xorshift;
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template <typename T>
|
|
xorshift<T>::xorshift (T seed):
|
|
m_state (seed)
|
|
{
|
|
if (!m_state)
|
|
throw std::invalid_argument ("xorshift seed must not be zero");
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
// setup the constants a, b, and c. we use the values from the example
|
|
// generators provided in Marsaglia's paper.
|
|
template <typename T>
|
|
struct constants;
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <>
|
|
struct constants<uint32_t>
|
|
{
|
|
static constexpr uint32_t a = 13u;
|
|
static constexpr uint32_t b = 17u;
|
|
static constexpr uint32_t c = 5u;
|
|
};
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <>
|
|
struct constants<uint64_t>
|
|
{
|
|
static constexpr uint64_t a = 13u;
|
|
static constexpr uint64_t b = 7u;
|
|
static constexpr uint64_t c = 17u;
|
|
};
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template <typename T>
|
|
typename xorshift<T>::result_type
|
|
xorshift<T>::operator() (void)
|
|
{
|
|
m_state ^= m_state >> constants<T>::a;
|
|
m_state ^= m_state << constants<T>::b;
|
|
m_state ^= m_state >> constants<T>::c;
|
|
|
|
CHECK_NEZ (m_state);
|
|
return m_state;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template <typename T>
|
|
void
|
|
xorshift<T>::discard (unsigned count)
|
|
{
|
|
while (count--)
|
|
(*this)();
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template struct cruft::rand::xorshift<uint32_t>;
|
|
template struct cruft::rand::xorshift<uint64_t>;
|