/* * 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 Danny Robson <danny@nerdcruft.net> */ #include "lcg.hpp" #include "../maths.hpp" using cruft::rand::lcg; /////////////////////////////////////////////////////////////////////////////// template <typename T> static constexpr bool is_coprime (T M, T C) { if (M == 0) return true; if (std::gcd (M, C) == 1u) return true; return false; } /////////////////////////////////////////////////////////////////////////////// template <typename T, T M, T A, T C> lcg<T,M,A,C>::lcg (T seed): m_x (seed) { // ensure this assertion isn't in a header, it could be pretty expensive // to evaluate often. static_assert (is_coprime (M, C), "multiplier and increment must be coprime"); } /////////////////////////////////////////////////////////////////////////////// template <typename T, T M, T A, T C> T lcg<T,M,A,C>::operator() (void) { m_x = (A * m_x + C); if (M != 0) m_x %= M; return m_x; } /////////////////////////////////////////////////////////////////////////////// template <typename T, T M, T A, T C> typename lcg<T,M,A,C>::result_type lcg<T,M,A,C>::min (void) { return std::numeric_limits<result_type>::min (); } //----------------------------------------------------------------------------- template <typename T, T M, T A, T C> typename lcg<T,M,A,C>::result_type lcg<T,M,A,C>::max (void) { return std::numeric_limits<result_type>::max (); } /////////////////////////////////////////////////////////////////////////////// template <typename T, T M, T A, T C> void lcg<T,M,A,C>::discard (unsigned count) { while (count--) (*this)(); } /////////////////////////////////////////////////////////////////////////////// template struct cruft::rand::lcg<uint32_t, cruft::pow(31,2), 1103515245, 12345>; template struct cruft::rand::lcg<uint64_t, 0ul, 6364136223846793005ul, 1ul>;