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blt-gp/include/blt/gp/selection.h

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#pragma once
/*
* Copyright (C) 2024 Brett Terpstra
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef BLT_GP_SELECTION_H
#define BLT_GP_SELECTION_H
#include <blt/gp/fwdecl.h>
#include <blt/gp/tree.h>
#include <blt/gp/config.h>
#include <blt/gp/random.h>
#include <blt/std/assert.h>
#include "blt/format/format.h"
#include <atomic>
namespace blt::gp
{
struct selector_args
{
gp_program& program;
const population_t& current_pop;
population_stats& current_stats;
prog_config_t& config;
random_t& random;
};
constexpr inline auto perform_elitism = [](const selector_args& args, population_t& next_pop)
{
auto& [program, current_pop, current_stats, config, random] = args;
if (config.elites > 0 && current_pop.get_individuals().size() >= config.elites)
{
static thread_local tracked_vector<std::pair<std::size_t, double>> values;
values.clear();
for (blt::size_t i = 0; i < config.elites; i++)
values.emplace_back(i, current_pop.get_individuals()[i].fitness.adjusted_fitness);
for (const auto& ind : blt::enumerate(current_pop.get_individuals()))
{
for (blt::size_t i = 0; i < config.elites; i++)
{
if (ind.second.fitness.adjusted_fitness >= values[i].second)
{
bool doesnt_contain = true;
for (blt::size_t j = 0; j < config.elites; j++)
{
if (ind.first == values[j].first)
doesnt_contain = false;
}
if (doesnt_contain)
values[i] = {ind.first, ind.second.fitness.adjusted_fitness};
break;
}
}
}
for (blt::size_t i = 0; i < config.elites; i++)
next_pop.get_individuals()[i].copy_fast(current_pop.get_individuals()[values[i].first].tree);
return config.elites;
}
return 0ul;
};
inline std::atomic<double> parent_fitness = 0;
inline std::atomic<double> child_fitness = 0;
template <typename Crossover, typename Mutation, typename Reproduction>
constexpr inline auto default_next_pop_creator = [](
selector_args& args, Crossover& crossover_selection, Mutation& mutation_selection, Reproduction& reproduction_selection,
tree_t& c1, tree_t* c2, const std::function<bool(const tree_t&, fitness_t&, size_t)>& test_fitness_func)
{
auto& [program, current_pop, current_stats, config, random] = args;
switch (random.get_i32(0, 3))
{
case 0:
if (c2 == nullptr)
return 0;
// everyone gets a chance once per loop.
if (random.choice(config.crossover_chance))
{
#ifdef BLT_TRACK_ALLOCATIONS
auto state = tracker.start_measurement_thread_local();
#endif
// crossover
const tree_t* p1;
const tree_t* p2;
double parent_val = 0;
do
{
p1 = &crossover_selection.select(program, current_pop);
p2 = &crossover_selection.select(program, current_pop);
fitness_t fitness1;
fitness_t fitness2;
test_fitness_func(*p1, fitness1, 0);
test_fitness_func(*p2, fitness2, 0);
parent_val = fitness1.adjusted_fitness + fitness2.adjusted_fitness;
// BLT_TRACE("%ld> P1 Fit: %lf, P2 Fit: %lf", val, fitness1.adjusted_fitness, fitness2.adjusted_fitness);
c1.copy_fast(*p1);
c2->copy_fast(*p2);
crossover_calls.value(1);
}
while (!config.crossover.get().apply(program, *p1, *p2, c1, *c2));
fitness_t fitness1;
fitness_t fitness2;
test_fitness_func(c1, fitness1, 0);
test_fitness_func(*c2, fitness2, 0);
const auto child_val = fitness1.adjusted_fitness + fitness2.adjusted_fitness;
auto old_parent_val = parent_fitness.load(std::memory_order_relaxed);
while (!parent_fitness.compare_exchange_weak(old_parent_val, old_parent_val + parent_val, std::memory_order_relaxed,
std::memory_order_relaxed))
{
}
auto old_child_val = child_fitness.load(std::memory_order_relaxed);
while (!child_fitness.compare_exchange_weak(old_child_val, old_child_val + child_val, std::memory_order_relaxed,
std::memory_order_relaxed))
{
}
// BLT_TRACE("%ld> C1 Fit: %lf, C2 Fit: %lf", val, fitness1.adjusted_fitness, fitness2.adjusted_fitness);
#ifdef BLT_TRACK_ALLOCATIONS
tracker.stop_measurement_thread_local(state);
crossover_calls.call();
if (state.getAllocatedByteDifference() != 0)
{
crossover_allocations.call(state.getAllocatedByteDifference());
crossover_allocations.set_value(std::max(crossover_allocations.get_value(), state.getAllocatedByteDifference()));
}
#endif
return 2;
}
break;
case 1:
if (random.choice(config.mutation_chance))
{
#ifdef BLT_TRACK_ALLOCATIONS
auto state = tracker.start_measurement_thread_local();
#endif
// mutation
const tree_t* p;
do
{
p = &mutation_selection.select(program, current_pop);
c1.copy_fast(*p);
mutation_calls.value(1);
}
while (!config.mutator.get().apply(program, *p, c1));
#ifdef BLT_TRACK_ALLOCATIONS
tracker.stop_measurement_thread_local(state);
mutation_calls.call();
if (state.getAllocationDifference() != 0)
{
mutation_allocations.call(state.getAllocatedByteDifference());
mutation_allocations.set_value(std::max(mutation_allocations.get_value(), state.getAllocatedByteDifference()));
}
#endif
return 1;
}
break;
case 2:
if (config.reproduction_chance > 0 && random.choice(config.reproduction_chance))
{
#ifdef BLT_TRACK_ALLOCATIONS
auto state = tracker.start_measurement_thread_local();
#endif
// reproduction
c1.copy_fast(reproduction_selection.select(program, current_pop));
#ifdef BLT_TRACK_ALLOCATIONS
tracker.stop_measurement_thread_local(state);
reproduction_calls.call();
reproduction_calls.value(1);
if (state.getAllocationDifference() != 0)
{
reproduction_allocations.call(state.getAllocatedByteDifference());
reproduction_allocations.set_value(std::max(reproduction_allocations.get_value(), state.getAllocatedByteDifference()));
}
#endif
return 1;
}
break;
default:
#if BLT_DEBUG_LEVEL > 0
BLT_ABORT("This is not possible!");
#else
BLT_UNREACHABLE;
#endif
}
return 0;
};
class selection_t
{
public:
/**
* @param program gp program to select with, used in randoms
* @param pop population to select from
* @param stats the populations statistics
* @return
*/
virtual const tree_t& select(gp_program& program, const population_t& pop) = 0;
/**
* Is run once on a single thread before selection begins. allows you to preprocess the generation for fitness metrics.
* TODO a method for parallel execution
*/
virtual void pre_process(gp_program&, population_t&)
{
}
virtual ~selection_t() = default;
};
class select_best_t final : public selection_t
{
public:
void pre_process(gp_program&, population_t&) override;
const tree_t& select(gp_program& program, const population_t& pop) override;
private:
std::atomic_uint64_t index = 0;
};
class select_worst_t final : public selection_t
{
public:
void pre_process(gp_program&, population_t&) override;
const tree_t& select(gp_program& program, const population_t& pop) override;
private:
std::atomic_uint64_t index = 0;
};
class select_random_t final : public selection_t
{
public:
const tree_t& select(gp_program& program, const population_t& pop) override;
};
class select_tournament_t final : public selection_t
{
public:
explicit select_tournament_t(const size_t selection_size = 3): selection_size(selection_size)
{
if (selection_size == 0)
BLT_ABORT("Unable to select with this size. Must select at least 1 individual_t!");
}
const tree_t& select(gp_program& program, const population_t& pop) override;
private:
const size_t selection_size;
};
class select_fitness_proportionate_t final : public selection_t
{
public:
const tree_t& select(gp_program& program, const population_t& pop) override;
};
}
#endif //BLT_GP_SELECTION_H
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