💿🐜 Antkeeper source code
https://antkeeper.com
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169 lines
3.7 KiB
169 lines
3.7 KiB
/*
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* Copyright (C) 2020 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_CHROMOSOME_HPP
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#define ANTKEEPER_CHROMOSOME_HPP
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#include "bit-math.hpp"
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#include <array>
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namespace dna
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{
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/**
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* Segregates the odd and even bits of a value.
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*
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* @param x Value to segregate.
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* @return Value with even bits of @p x in the lower half, and odd bits in the upper half.
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*/
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template <class T>
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T segregate(T x)
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{
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T odd = deinterleave(x);
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T even = deinterleave(x >> 1);
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return odd | (even << (sizeof(T) << 2));
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}
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/**
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* Interleaves bits of the lower and upper halves of a value.
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*
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* @param x Value to desegregate.
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* @return Value with bits from the upper half of @p x interleaved with bits from the lower half.
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*/
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template <class T>
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T desegregate(T x)
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{
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return interleave<T>(x, x >> (sizeof(T) << 2));
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}
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/**
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* Replicates each bit in the lower half of a value.
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*
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* @param x Value to replicate.
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* @return Value of @p x interleaved with itself.
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*/
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template <class T>
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T replicate(T x)
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{
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x = bit_expand(x);
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return x | (x << 1);
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}
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/**
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* Performs
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*/
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template <class T>
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std::array<T, 4> meiosis(T x, T mask)
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{
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x = segregate(x);
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T xl = x & (sizeof(T) << 2);
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T xh = x >> (sizeof(T) << 2);
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T a = xl;
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T b = crossover_n(xl, xh, mask);
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T c = crossover_n(xh, xl, mask);
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T d = xh;
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return {a, b, c, d};
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}
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/**
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*
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*
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* @param a 2c chromosome of first parent.
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* @param b 2c chromosome of second parent.
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* @param g Uniform random bit generator. `g()` will be called three times.
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* @return 2c chromosome of child.
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*/
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template <class T, class URBG>
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T reproduce(T a, T b, URBG&& g)
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{
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auto gametes_a = meiosis(a, static_cast<T>(g()));
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auto gametes_b = meiosis(b, static_cast<T>(g()));
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T i = static_cast<T>(g());
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T ca = gametes_a[i & 3];
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T cb = gametes_b[(i >> 2) & 3];
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return interleave(ca, cb);
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}
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/**
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* Performs a single-point crossover between two values.
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*
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* @param a First value.
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* @param b Second value.
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* @param i Index of the crossover point.
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* @return Crossed over value.
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*/
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template <class T>
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constexpr T crossover(T a, T b, int i) noexcept;
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/**
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* Performs an n-point crossover between two values.
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*
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* @param a First value.
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* @param b Second value.
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* @param mask Bit mask with set bits marking crossover points.
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* @return Crossed over value.
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*/
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template <class T>
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constexpr T crossover_n(T a, T b, T mask) noexcept;
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/**
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* Mutates a value by flipping a single bit.
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*
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* @param x Value to mutate.
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* @param i Index of the bit to flip.
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* @return Mutated copy of @p x.
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*/
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template <class T>
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T mutate(T x, int i);
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template <class T>
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inline constexpr T crossover(T a, T b, int i) noexcept
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{
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T mask = (T(1) << i) - 1;
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return bit_merge(b, a, mask);
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}
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template <class T>
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constexpr T crossover_n(T a, T b, T mask) noexcept
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{
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T merge = ~T(0) * parity(mask);
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while (mask)
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{
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merge ^= (mask ^ (mask - 1)) >> 1;
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mask &= mask - 1;
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}
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return bit_merge(a, b, merge);
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}
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template <class T>
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inline T mutate(T x, int i)
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{
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return x ^ (T(1) << i);
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}
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} // namespace dna
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#endif // ANTKEEPER_CHROMOSOME_HPP
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