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better permutation crossover implementation
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- ~10% for position on tsp439
- ~60% for cycle on tsp439
- ~2% for edge on tsp439
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@KRM7
KRM7 committed Sep 9, 2024
1 parent 457e10b commit 51fc547
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Showing 3 changed files with 229 additions and 150 deletions.
234 changes: 90 additions & 144 deletions src/crossover/crossover_impl.hpp
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Original file line number Diff line number Diff line change
@@ -1,15 +1,14 @@
/* Copyright (c) 2022 Krisztián Rugási. Subject to the MIT License. */

#ifndef GA_CROSSOVER_DTL_HPP
#define GA_CROSSOVER_DTL_HPP
#ifndef GAPP_CROSSOVER_DTL_HPP
#define GAPP_CROSSOVER_DTL_HPP

#include "neighbour_list.hpp"
#include "../core/candidate.hpp"
#include "../utility/small_vector.hpp"
#include "../utility/dynamic_bitset.hpp"
#include <vector>
#include <span>
#include <unordered_map>
#include <type_traits>
#include <concepts>
#include <cstddef>

Expand Down Expand Up @@ -55,27 +54,19 @@ namespace gapp::crossover::dtl
Candidate<T> positionCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2, std::span<const size_t> indices);


/* Find the indices of genes in the chromosomes chrom1 and chrom2 which belong to odd cycles. Used in the cycle crossover operator. */
/* Find the indices of genes in the chromosomes chrom1 and chrom2 which belong to odd cycles. */
template<typename T>
std::vector<size_t> findOddCycleIndices(const Chromosome<T>& chrom1, const Chromosome<T>& chrom2);

/* Find the indices of genes in the chromosomes chrom1 and chrom2 which belong to odd cycles. */
template<std::unsigned_integral T>
std::vector<size_t> findOddCycleIndices(const Chromosome<T>& chrom1, const Chromosome<T>& chrom2);

/* Implementation of the cycle crossover for any gene type. */
template<typename T>
CandidatePair<T> cycleCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2);


/* A list of neighbours for a gene. */
template<typename T>
class NeighbourList;

/* A list of neighbours for an unsigned integer gene. */
template<std::unsigned_integral T>
class NeighbourList<T>;

/* Conctruct the neighbour lists of each gene based on 2 chromosomes. The first and last elements are considered neighbours. */
template<typename T, typename R = std::conditional_t<std::is_unsigned_v<T>, std::vector<NeighbourList<T>>, std::unordered_map<T, NeighbourList<T>>>>
R makeNeighbourLists(const Chromosome<T>& chrom1, const Chromosome<T>& chrom2);

/* Implementation of the edge crossover for any gene type, only generates a single child. */
template<typename T>
Candidate<T> edgeCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2);
Expand All @@ -100,9 +91,7 @@ namespace gapp::crossover::dtl

#include "../utility/algorithm.hpp"
#include "../utility/functional.hpp"
#include "../utility/iterators.hpp"
#include "../utility/utility.hpp"
#include <array>
#include <unordered_set>
#include <algorithm>

Expand Down Expand Up @@ -174,6 +163,24 @@ namespace gapp::crossover::dtl
}


template<std::unsigned_integral T>
bool isValidIntegerPermutation(const Chromosome<T>& chrom)
{
if (chrom.empty()) return true;

if (*std::min_element(chrom.begin(), chrom.end()) != 0) return false;
if (*std::max_element(chrom.begin(), chrom.end()) != chrom.size() - 1) return false;

detail::dynamic_bitset present(chrom.size());
for (const T& val : chrom)
{
if (present[val]) return false;
present[val] = true;
}

return true;
}

template<typename T>
Candidate<T> order1CrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2, size_t first, size_t last)
{
Expand Down Expand Up @@ -210,11 +217,10 @@ namespace gapp::crossover::dtl
const size_t chrom_len = parent1.chromosome.size();
const size_t range_len = last - first;

/* The genes have to be unique unsigned integers in the range [0, chrom_len). */
GAPP_ASSERT(first <= last && last <= chrom_len);
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());
GAPP_ASSERT(*std::min_element(parent1.chromosome.begin(), parent1.chromosome.end()) == 0);
GAPP_ASSERT(*std::max_element(parent1.chromosome.begin(), parent1.chromosome.end()) == chrom_len - 1);
GAPP_ASSERT(isValidIntegerPermutation(parent1.chromosome));
GAPP_ASSERT(isValidIntegerPermutation(parent2.chromosome));

detail::dynamic_bitset is_direct(chrom_len);
for (size_t idx = first; idx != last; idx++) is_direct[parent1.chromosome[idx]] = true;
Expand Down Expand Up @@ -266,11 +272,10 @@ namespace gapp::crossover::dtl
{
const size_t chrom_len = parent1.chromosome.size();

/* The genes have to be unique unsigned integers in the range [0, chrom_len). */
GAPP_ASSERT(first <= last && last <= chrom_len);
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());
GAPP_ASSERT(*std::min_element(parent1.chromosome.begin(), parent1.chromosome.end()) == 0);
GAPP_ASSERT(*std::max_element(parent1.chromosome.begin(), parent1.chromosome.end()) == chrom_len - 1);
GAPP_ASSERT(isValidIntegerPermutation(parent1.chromosome));
GAPP_ASSERT(isValidIntegerPermutation(parent2.chromosome));

detail::dynamic_bitset is_direct(chrom_len);
for (size_t idx = first; idx != last; idx++) is_direct[parent1.chromosome[idx]] = true;
Expand Down Expand Up @@ -317,24 +322,32 @@ namespace gapp::crossover::dtl
Candidate<T> positionCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2, std::span<const size_t> indices)
{
const size_t chrom_len = parent1.chromosome.size();

/* The genes have to be unique unsigned integers in the range [0, chrom_len). */

GAPP_ASSERT(std::all_of(indices.begin(), indices.end(), detail::between(0_sz, chrom_len - 1)));
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());
GAPP_ASSERT(*std::min_element(parent1.chromosome.begin(), parent1.chromosome.end()) == 0);
GAPP_ASSERT(*std::max_element(parent1.chromosome.begin(), parent1.chromosome.end()) == chrom_len - 1);
GAPP_ASSERT(isValidIntegerPermutation(parent1.chromosome));
GAPP_ASSERT(isValidIntegerPermutation(parent2.chromosome));

detail::dynamic_bitset is_direct(chrom_len);
for (size_t idx : indices) is_direct[parent1.chromosome[idx]] = true;

small_vector<size_t> next_indirect(chrom_len);
for (ptrdiff_t indirect = -1, i = chrom_len - 1; i >= 0; i--)
{
const T gene = parent1.chromosome[i];

indirect = is_direct[gene] ? indirect : i;
next_indirect[i] = indirect;
}

Candidate child = parent1;

for (auto child_pos = child.chromosome.begin(); const T& gene : parent2.chromosome)
for (size_t child_pos = 0; T gene : parent2.chromosome)
{
if (!is_direct[gene])
{
while (is_direct[*child_pos]) ++child_pos;
*child_pos++ = gene;
child_pos = next_indirect[child_pos];
child.chromosome[child_pos++] = gene;
}
}

Expand Down Expand Up @@ -379,137 +392,71 @@ namespace gapp::crossover::dtl
return odd_indices;
}

template<typename T>
CandidatePair<T> cycleCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2)
{
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());

const auto odd_cycle_idxs = dtl::findOddCycleIndices(parent1.chromosome, parent2.chromosome);

Candidate child1 = parent1;
Candidate child2 = parent2;

for (size_t idx : odd_cycle_idxs)
{
using std::swap;
swap(child1.chromosome[idx], child2.chromosome[idx]);
}

return { std::move(child1), std::move(child2) };
}


template<typename T>
class NeighbourList : public detail::container_interface<NeighbourList<T>>
template<std::unsigned_integral T>
std::vector<size_t> findOddCycleIndices(const Chromosome<T>& chrom1, const Chromosome<T>& chrom2)
{
public:
using value_type = T;
using reference = T&;
using const_reference = const T&;
GAPP_ASSERT(chrom1.size() == chrom2.size());
GAPP_ASSERT(isValidIntegerPermutation(chrom1));
GAPP_ASSERT(isValidIntegerPermutation(chrom2));

using size_type = std::size_t;
using difference_type = std::ptrdiff_t;
const size_t chrom_len = chrom1.size();

using iterator = typename std::vector<value_type>::iterator;
using const_iterator = typename std::vector<value_type>::const_iterator;
using reverse_iterator = typename std::vector<value_type>::reverse_iterator;
using const_reverse_iterator = typename std::vector<value_type>::const_reverse_iterator;
std::vector<size_t> odd_indices;
odd_indices.reserve(chrom_len / 2);

NeighbourList() { neighbours_.reserve(4); }
detail::dynamic_bitset deleted(chrom_len);
size_t num_deleted = 0;

void add(const T& value)
std::vector index_lookup(chrom_len, 0_sz);
for (size_t i = 0; i < chrom_len; i++)
{
if (!detail::contains(neighbours_.cbegin(), neighbours_.cend(), value))
{
neighbours_.push_back(value);
}
index_lookup[chrom1[i]] = i;
}

void remove(const T& value) { detail::erase_first_stable(neighbours_, value); }

constexpr auto begin() noexcept { return neighbours_.begin(); }
constexpr auto end() noexcept { return neighbours_.end(); }
constexpr auto begin() const noexcept { return neighbours_.begin(); }
constexpr auto end() const noexcept { return neighbours_.end(); }
for (bool odd_cycle = false; num_deleted < chrom_len; odd_cycle ^= 1)
{
size_t pos = deleted.find_first(false);
T cycle_start = chrom1[pos];

private:
small_vector<T> neighbours_;
};
deleted[pos] = true;
num_deleted++;

template<std::unsigned_integral T>
class NeighbourList<T> : public detail::iterator_interface<NeighbourList<T>>
{
public:
void add(T value)
{
GAPP_ASSERT(value != EMPTY);
if (odd_cycle) odd_indices.push_back(pos);

/* Assume that EMPTY values are at the back. */
for (T& neighbour : neighbours_)
while (chrom2[pos] != cycle_start)
{
if (neighbour == value) return;
if (neighbour == EMPTY)
{
neighbour = value;
return;
}
}
GAPP_UNREACHABLE();
}
pos = index_lookup[chrom2[pos]];

void remove(T value)
{
GAPP_ASSERT(value != EMPTY);
deleted[pos] = true;
num_deleted++;

for (T& neighbour : neighbours_)
{
neighbour = (neighbour == value) ? EMPTY : neighbour;
if (odd_cycle) odd_indices.push_back(pos);
}
}

constexpr size_t size() const noexcept
{
return std::count_if(neighbours_.begin(), neighbours_.end(), detail::not_equal_to(EMPTY));
}

constexpr bool empty() const noexcept { return size() == 0; }

constexpr auto begin() noexcept { return neighbours_.begin(); }
constexpr auto end() noexcept { return neighbours_.end(); }
constexpr auto begin() const noexcept { return neighbours_.begin(); }
constexpr auto end() const noexcept { return neighbours_.end(); }

static constexpr T EMPTY = T(-1);

private:
std::array<T, 4> neighbours_{ EMPTY, EMPTY, EMPTY, EMPTY };
};
return odd_indices;
}

template<typename T, typename R>
R makeNeighbourLists(const Chromosome<T>& chrom1, const Chromosome<T>& chrom2)
template<typename T>
CandidatePair<T> cycleCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2)
{
GAPP_ASSERT(chrom1.size() == chrom2.size());
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());

R nb_lists(chrom1.size());
const auto odd_cycle_idxs = dtl::findOddCycleIndices(parent1.chromosome, parent2.chromosome);

nb_lists[chrom1.front()].add(chrom1[1]);
nb_lists[chrom2.front()].add(chrom2[1]);
Candidate child1 = parent1;
Candidate child2 = parent2;

for (size_t i = 1; i < chrom1.size() - 1; i++)
for (size_t idx : odd_cycle_idxs)
{
nb_lists[chrom1[i]].add(chrom1[i - 1]);
nb_lists[chrom1[i]].add(chrom1[i + 1]);

nb_lists[chrom2[i]].add(chrom2[i - 1]);
nb_lists[chrom2[i]].add(chrom2[i + 1]);
using std::swap;
swap(child1.chromosome[idx], child2.chromosome[idx]);
}

nb_lists[chrom1.back()].add(*(chrom1.end() - 2));
nb_lists[chrom2.back()].add(*(chrom2.end() - 2));

return nb_lists;
return { std::move(child1), std::move(child2) };
}


template<typename T>
Candidate<T> edgeCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2)
{
Expand Down Expand Up @@ -551,10 +498,9 @@ namespace gapp::crossover::dtl
{
const size_t chrom_len = parent1.chromosome.size();

/* The genes have to be unique unsigned integers in the range [0, chrom_len). */
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());
GAPP_ASSERT(*std::min_element(parent1.chromosome.begin(), parent1.chromosome.end()) == 0);
GAPP_ASSERT(*std::max_element(parent1.chromosome.begin(), parent1.chromosome.end()) == chrom_len - 1);
GAPP_ASSERT(isValidIntegerPermutation(parent1.chromosome));
GAPP_ASSERT(isValidIntegerPermutation(parent2.chromosome));

auto nb_lists = makeNeighbourLists(parent1.chromosome, parent2.chromosome);

Expand All @@ -567,7 +513,7 @@ namespace gapp::crossover::dtl
while (child.chromosome.size() != chrom_len)
{
T last_gene = child.chromosome.back();
T next_gene = T(is_used.find_first(false));
T next_gene = is_used.find_first(false);

for (T neighbour : nb_lists[last_gene])
{
Expand All @@ -588,6 +534,7 @@ namespace gapp::crossover::dtl
return child;
}


template<typename T>
Candidate<T> pmxCrossoverImpl(const Candidate<T>& parent1, const Candidate<T>& parent2, size_t first, size_t last)
{
Expand Down Expand Up @@ -624,11 +571,10 @@ namespace gapp::crossover::dtl
{
const size_t chrom_len = parent1.chromosome.size();

/* The genes have to be unique unsigned integers in the range [0, chrom_len). */
GAPP_ASSERT(parent1.chromosome.size() == parent2.chromosome.size());
GAPP_ASSERT(first <= last && last <= parent1.chromosome.size());
GAPP_ASSERT(*std::min_element(parent1.chromosome.begin(), parent1.chromosome.end()) == 0);
GAPP_ASSERT(*std::max_element(parent1.chromosome.begin(), parent1.chromosome.end()) == chrom_len - 1);
GAPP_ASSERT(isValidIntegerPermutation(parent1.chromosome));
GAPP_ASSERT(isValidIntegerPermutation(parent2.chromosome));

Candidate child = parent2;

Expand Down Expand Up @@ -663,4 +609,4 @@ namespace gapp::crossover::dtl

} // namespace gapp::crossover::dtl

#endif // !GA_CROSSOVER_DTL_HPP
#endif // !GAPP_CROSSOVER_DTL_HPP
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