solidity/tools/yulPhaser/GeneticAlgorithms.h
2021-05-17 11:35:07 +01:00

226 lines
8.2 KiB
C++

/*
This file is part of solidity.
solidity 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.
solidity 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 solidity. If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0
/**
* Contains an abstract base class representing a genetic algorithm and its concrete implementations.
*/
#pragma once
#include <tools/yulPhaser/Mutations.h>
#include <tools/yulPhaser/Population.h>
#include <cstddef>
#include <optional>
namespace solidity::phaser
{
enum class CrossoverChoice
{
SinglePoint,
TwoPoint,
Uniform,
};
std::function<Crossover> buildCrossoverOperator(
CrossoverChoice _choice,
std::optional<double> _uniformCrossoverSwapChance
);
std::function<SymmetricCrossover> buildSymmetricCrossoverOperator(
CrossoverChoice _choice,
std::optional<double> _uniformCrossoverSwapChance
);
/**
* Abstract base class for genetic algorithms.
* The main feature is the @a runNextRound() method that executes one round of the algorithm,
* on the supplied population.
*/
class GeneticAlgorithm
{
public:
GeneticAlgorithm() {}
GeneticAlgorithm(GeneticAlgorithm const&) = delete;
GeneticAlgorithm& operator=(GeneticAlgorithm const&) = delete;
virtual ~GeneticAlgorithm() = default;
/// The method that actually implements the algorithm. Should accept the current population in
/// @a _population and return the updated one after the round.
virtual Population runNextRound(Population _population) = 0;
};
/**
* Completely random genetic algorithm,
*
* The algorithm simply replaces the worst chromosomes with entirely new ones, generated
* randomly and not based on any member of the current population. Only a constant proportion of the
* chromosomes (the elite) is preserved in each round.
*
* Preserves the size of the population. You can use @a elitePoolSize to make the algorithm
* generational (replacing most members in each round) or steady state (replacing only one member).
* Both versions are equivalent in terms of the outcome but the generational one converges in a
* smaller number of rounds while the steady state one does less work per round. This may matter
* in case of metrics that take a long time to compute though in case of this particular
* algorithm the same result could also be achieved by simply making the population smaller.
*/
class RandomAlgorithm: public GeneticAlgorithm
{
public:
struct Options
{
double elitePoolSize; ///< Percentage of the population treated as the elite
size_t minChromosomeLength; ///< Minimum length of newly generated chromosomes
size_t maxChromosomeLength; ///< Maximum length of newly generated chromosomes
bool isValid() const
{
return (
0 <= elitePoolSize && elitePoolSize <= 1.0 &&
minChromosomeLength <= maxChromosomeLength
);
}
};
explicit RandomAlgorithm(Options const& _options):
m_options(_options)
{
assert(_options.isValid());
}
Options const& options() const { return m_options; }
Population runNextRound(Population _population) override;
private:
Options m_options;
};
/**
* A generational, elitist genetic algorithm that replaces the population by mutating and crossing
* over chromosomes from the elite.
*
* The elite consists of individuals not included in the crossover and mutation pools.
* The crossover operator used is @a randomPointCrossover. The mutation operator is randomly chosen
* from three possibilities: @a geneRandomisation, @a geneDeletion or @a geneAddition (with
* configurable probabilities). Each mutation also has a parameter determining the chance of a gene
* being affected by it.
*/
class GenerationalElitistWithExclusivePools: public GeneticAlgorithm
{
public:
struct Options
{
double mutationPoolSize; ///< Percentage of population to regenerate using mutations in each round.
double crossoverPoolSize; ///< Percentage of population to regenerate using crossover in each round.
double randomisationChance; ///< The chance of choosing @a geneRandomisation as the mutation to perform
double deletionVsAdditionChance; ///< The chance of choosing @a geneDeletion as the mutation if randomisation was not chosen.
double percentGenesToRandomise; ///< The chance of any given gene being mutated in gene randomisation.
double percentGenesToAddOrDelete; ///< The chance of a gene being added (or deleted) in gene addition (or deletion).
CrossoverChoice crossover; ///< The crossover operator to use.
std::optional<double> uniformCrossoverSwapChance; ///< Chance of a pair of genes being swapped in uniform crossover.
bool isValid() const
{
return (
0 <= mutationPoolSize && mutationPoolSize <= 1.0 &&
0 <= crossoverPoolSize && crossoverPoolSize <= 1.0 &&
0 <= randomisationChance && randomisationChance <= 1.0 &&
0 <= deletionVsAdditionChance && deletionVsAdditionChance <= 1.0 &&
0 <= percentGenesToRandomise && percentGenesToRandomise <= 1.0 &&
0 <= percentGenesToAddOrDelete && percentGenesToAddOrDelete <= 1.0 &&
0 <= uniformCrossoverSwapChance && uniformCrossoverSwapChance <= 1.0 &&
mutationPoolSize + crossoverPoolSize <= 1.0
);
}
};
GenerationalElitistWithExclusivePools(Options const& _options):
m_options(_options)
{
assert(_options.isValid());
}
Options const& options() const { return m_options; }
Population runNextRound(Population _population) override;
private:
Options m_options;
};
/**
* A typical genetic algorithm that works in three distinct phases, each resulting in a new,
* modified population:
* - selection: chromosomes are selected from the population with probability proportional to their
* fitness. A chromosome can be selected more than once. The new population has the same size as
* the old one.
* - crossover: first, for each chromosome we decide whether it undergoes crossover or not
* (according to crossover chance parameter). Then each selected chromosome is randomly paired
* with one other selected chromosome. Each pair produces a pair of children and gets replaced by
* it in the population.
* - mutation: we go over each gene in the population and independently decide whether to mutate it
* or not (according to mutation chance parameters). This is repeated for every mutation type so
* one gene can undergo mutations of multiple types in a single round.
*
* This implementation also has the ability to preserve the top chromosomes in each round.
*/
class ClassicGeneticAlgorithm: public GeneticAlgorithm
{
public:
struct Options
{
double elitePoolSize; ///< Percentage of the population treated as the elite.
double crossoverChance; ///< The chance of a particular chromosome being selected for crossover.
double mutationChance; ///< The chance of a particular gene being randomised in @a geneRandomisation mutation.
double deletionChance; ///< The chance of a particular gene being deleted in @a geneDeletion mutation.
double additionChance; ///< The chance of a particular gene being added in @a geneAddition mutation.
CrossoverChoice crossover; ///< The crossover operator to use
std::optional<double> uniformCrossoverSwapChance; ///< Chance of a pair of genes being swapped in uniform crossover.
bool isValid() const
{
return (
0 <= elitePoolSize && elitePoolSize <= 1.0 &&
0 <= crossoverChance && crossoverChance <= 1.0 &&
0 <= mutationChance && mutationChance <= 1.0 &&
0 <= deletionChance && deletionChance <= 1.0 &&
0 <= additionChance && additionChance <= 1.0 &&
0 <= uniformCrossoverSwapChance && uniformCrossoverSwapChance <= 1.0
);
}
};
ClassicGeneticAlgorithm(Options const& _options):
m_options(_options)
{
assert(_options.isValid());
}
Options const& options() const { return m_options; }
Population runNextRound(Population _population) override;
private:
static Population select(Population _population, size_t _selectionSize);
Options m_options;
};
}