Danny Robson
f6056153e3
This places, at long last, the core library code into the same namespace as the extended library code.
84 lines
2.1 KiB
C++
84 lines
2.1 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#include "lcg.hpp"
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#include "../maths.hpp"
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using cruft::rand::lcg;
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///////////////////////////////////////////////////////////////////////////////
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template <typename T>
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static constexpr
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bool is_coprime (T M, T C)
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{
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if (M == 0)
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return true;
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if (std::gcd (M, C) == 1u)
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return true;
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return false;
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename T, T M, T A, T C>
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lcg<T,M,A,C>::lcg (T seed):
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m_x (seed)
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{
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// ensure this assertion isn't in a header, it could be pretty expensive
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// to evaluate often.
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static_assert (is_coprime (M, C),
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"multiplier and increment must be coprime");
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename T, T M, T A, T C>
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T
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lcg<T,M,A,C>::operator() (void)
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{
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m_x = (A * m_x + C);
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if (M != 0)
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m_x %= M;
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return m_x;
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename T, T M, T A, T C>
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typename lcg<T,M,A,C>::result_type
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lcg<T,M,A,C>::min (void)
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{
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return std::numeric_limits<result_type>::min ();
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}
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//-----------------------------------------------------------------------------
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template <typename T, T M, T A, T C>
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typename lcg<T,M,A,C>::result_type
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lcg<T,M,A,C>::max (void)
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{
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return std::numeric_limits<result_type>::max ();
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename T, T M, T A, T C>
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void
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lcg<T,M,A,C>::discard (unsigned count)
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{
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while (count--)
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(*this)();
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}
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///////////////////////////////////////////////////////////////////////////////
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template struct cruft::rand::lcg<uint32_t, cruft::pow(31,2), 1103515245, 12345>;
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template struct cruft::rand::lcg<uint64_t, 0ul, 6364136223846793005ul, 1ul>;
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