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59 lines
2.0 KiB
C++
59 lines
2.0 KiB
C++
/*
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* Created by Martin on 30/08/2017.
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*
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* Distributed under the Boost Software License, Version 1.0. (See accompanying
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* file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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*/
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#ifndef TWOBLUECUBES_CATCH_RANDOM_NUMBER_GENERATOR_H_INCLUDED
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#define TWOBLUECUBES_CATCH_RANDOM_NUMBER_GENERATOR_H_INCLUDED
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#include <cstdint>
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namespace Catch {
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// This is a simple implementation of C++11 Uniform Random Number
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// Generator. It does not provide all operators, because Catch2
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// does not use it, but it should behave as expected inside stdlib's
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// distributions.
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// The implementation is based on the PCG family (http://pcg-random.org)
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class SimplePcg32 {
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using state_type = std::uint64_t;
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public:
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using result_type = std::uint32_t;
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static constexpr result_type (min)() {
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return 0;
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}
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static constexpr result_type (max)() {
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return static_cast<result_type>(-1);
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}
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// Provide some default initial state for the default constructor
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SimplePcg32():SimplePcg32(0xed743cc4U) {}
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explicit SimplePcg32(result_type seed_);
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void seed(result_type seed_);
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void discard(uint64_t skip);
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result_type operator()();
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private:
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friend bool operator==(SimplePcg32 const& lhs, SimplePcg32 const& rhs);
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friend bool operator!=(SimplePcg32 const& lhs, SimplePcg32 const& rhs);
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// In theory we also need operator<< and operator>>
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// In practice we do not use them, so we will skip them for now
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std::uint64_t m_state;
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// This part of the state determines which "stream" of the numbers
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// is chosen -- we take it as a constant for Catch2, so we only
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// need to deal with seeding the main state.
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// Picked by reading 8 bytes from `/dev/random` :-)
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static const std::uint64_t s_inc = (0x13ed0cc53f939476ULL << 1ULL) | 1ULL;
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};
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} // end namespace Catch
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#endif // TWOBLUECUBES_CATCH_RANDOM_NUMBER_GENERATOR_H_INCLUDED
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