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• gaft-master
  • .coveragerc
  • examples
    • ex01
      • ex01.py
      • plot_animation.py
      • plot_envolution_curve.py
      • best_fit.py
    • ex02
      • plot_envolution_curve.py
      • ex02.py
      • plot_surf.py
      • best_fit.py
    • 1D_optimization_example.ipynb
  • .gitmodules
  • gaft
    • engine.py
    • components
      • population.py
      • __init__.py
      • binary_individual.py
      • individual.py
      • decimal_individual.py
    • operators
      • crossover
        • uniform_crossover.py
        • __init__.py
      • selection
        • linear_ranking_selection.py
        • roulette_wheel_selection.py
        • exponential_ranking_selection.py
        • tournament_selection.py
        • __init__.py
      • mutation
        • flip_bit_mutation.py
        • __init__.py
      • __init__.py
    • analysis
      • console_output.py
      • __init__.py
      • fitness_store.py
    • __init__.py
    • tests
      • population_test.py
      • individual_test.py
      • mpiutil_test.py
      • roulette_wheel_selection_test.py
      • uniform_crossover_test.py
      • linear_scaling_test.py
      • exponential_ranking_selection_test.py
      • dynamic_linear_scaling_test.py
      • flip_bit_mutation_test.py
      • test_all.py
      • __init__.py
      • engine_test.py
      • linear_ranking_selection_test.py
      • flip_bit_big_mutation_test.py
      • tournament_selection_test.py
    • mpiutil.py
    • plugin_interfaces
      • metaclasses.py
      • analysis.py
      • operators
        • selection.py
        • crossover.py
        • mutation.py
        • __init__.py
      • __init__.py
  • LICENSE
  • CHANGELOG.md
  • README.rst
  • setup.py
  • setup.cfg
  • .travis.yml
  • gasol
    • src
      • mpiutils.cpp
      • individual.h
      • selection.cpp
      • crossover.h
      • engine.h
      • individual.cpp
      • mpiutils.h
      • mutation.h
      • engine.cpp
      • crossover.cpp
      • selection.h
      • population.h
      • population.cpp
      • mutation.cpp
      • CMakeLists.txt
      • mpih.h
    • example
      • 1d_search.cpp
      • CMakeLists.txt
    • CMakeLists.txt
    • README.md
    • unittest
      • mpiutils_test.cpp
      • engine_test.cpp
      • individual_test.cpp
      • googletest
      • population_test.cpp
      • CMakeLists.txt
      • selection_test.cpp
      • gasol_test.cpp
      • crossover_test.cpp
      • mutation_test.cpp
  • .gitignore
  • docs
  • INSTALL.md
  • MANIFEST.in

#!/usr/bin/env python
# -*- coding: utf-8 -*-

''' Roulette Wheel Selection implementation. '''

from random import random
from bisect import bisect_right
from itertools import accumulate

from ...plugin_interfaces.operators.selection import Selection

class RouletteWheelSelection(Selection):
    ''' Selection operator with fitness proportionate selection(FPS) or
    so-called roulette-wheel selection implementation.
    '''
    def __init__(self):
        pass

    def select(self, population, fitness):
        ''' Select a pair of parent using FPS algorithm.

        :param population: Population where the selection operation occurs.
        :type population: :obj:`gaft.components.Population`

        :return: Selected parents (a father and a mother)
        :rtype: list of :obj:`gaft.components.IndividualBase`
        '''
        # Normalize fitness values for all individuals.
        fit = population.all_fits(fitness)
        min_fit = min(fit)
        fit = [(i - min_fit) for i in fit]

        # Create roulette wheel.
        sum_fit = sum(fit)
        wheel = list(accumulate([i/sum_fit for i in fit]))

        # Select a father and a mother.
        father_idx = bisect_right(wheel, random())
        father = population[father_idx]
        mother_idx = (father_idx + 1) % len(wheel)
        mother = population[mother_idx]

        return father, mother