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49 lines
955 B
49 lines
955 B
4 years ago
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#include <rng/impl.hpp>
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#include <rng/frng.hpp>
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#include <cmath>
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template<std::size_t N>
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constexpr inline double dot(const std::array<double, N>& v, const std::array<double, N>& u)
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{
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double res=0;
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for(std::size_t i=0;i<N;i++)
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{
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res += v[i] * u[i];
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}
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return res;
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}
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inline constexpr double fract(double x)
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{
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return x - floor(x);
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}
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namespace rng {
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inline constexpr double sample_double(const std::array<double, 2>& state)
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{
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const constexpr std::array<double, 2> vec2 = { 12.9898, 78.223 };
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return fract(sin(dot(state, vec2)) * 43758.5453);
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}
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inline void update_state(std::array<double, 2>& state, double r)
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{
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float v1 = (float)state[0];
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float v2 = (float)state[1];
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std::array<double, 2> nvec = {
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r,
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(double)v2,
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};
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state[0] = sample_double(nvec);
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nvec[1] = (double)v1;
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state[1] = sample_double(nvec);
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}
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double frng::sample()
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{
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double res = sample_double(state);
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update_state(state, res);
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return res;
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}
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}
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