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"""
Selection operator implementation.
"""
import random
import numpy as np
[docs]
def tournament_selection_min(pool_size):
"""
Returns a function that performs tournament selection to select an individual with the lowest fitness from a
population.
Parameters
----------
pool_size : int
Number of individuals participating in the tournament.
Returns
-------
Callable
A function ('ts') that elects the individual with the lowest fitness from a randomly chosen pool.
Parameters
----------
pop : Population
The population from which individuals are drawn.
Returns
-------
Individual
The individual with the lowest fitness in the pool.
Notes
-----
The returned function performs tournament selection by receiving a population and returning the best of {pool_size}
randomly selected individuals.
"""
def ts(pop):
"""
Selects the individual with the lowest fitness from a randomly chosen pool.
Parameters
----------
pop : Population
The population from which individuals are drawn.
Returns
-------
Individual
The individual with the lowest fitness in the pool.
"""
pool = random.choices(pop.population, k=pool_size)
return pool[np.argmin([ind.fitness for ind in pool])]
return ts
[docs]
def tournament_selection_max(pool_size):
"""
Returns a function that performs tournament selection to select an individual with the highest fitness from a
population.
Parameters
----------
pool_size : int
Number of individuals participating in the tournament.
Returns
-------
Callable
A function ('ts') that elects the individual with the highest fitness from a randomly chosen pool.
Parameters
----------
pop : Population
The population from which individuals are drawn.
Returns
-------
Individual
The individual with the lowest fitness in the pool.
Notes
-----
The returned function performs tournament selection by receiving a population and returning the best of {pool_size}
randomly selected individuals.
"""
def ts(pop):
"""
Selects the individual with the highest fitness from a randomly chosen pool.
Parameters
----------
pop : Population
The population from which individuals are drawn.
Returns
-------
Individual
The individual with the highest fitness in the pool.
"""
pool = random.choices(pop.population, k=pool_size)
return pool[np.argmax([ind.fitness for ind in pool])]
return ts