Source code for surrogate.crossover.cxOrdered

# Copyright 2016 Quan Pan
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# Author: Quan Pan <>
# License: Apache License, Version 2.0
# Create: 2016-12-02

import random

[docs]def cxOrdered(var1, var2): """Executes an ordered crossover (OX) on the input individuals. The two individuals are modified in place. This crossover expects :term:`sequence` individuals of indices, the result for any other type of individuals is unpredictable. :param var1: The first variable participating in the crossover. :param var2: The second variable participating in the crossover. :returns: A tuple of two variables. Moreover, this crossover generates holes in the input individuals. A hole is created when an attribute of an individual is between the two crossover points of the other individual. Then it rotates the element so that all holes are between the crossover points and fills them with the removed elements in order. For more details see [Goldberg1989]_. This function uses the :func:`~random.sample` function from the python base :mod:`random` module. .. [Goldberg1989] Goldberg. Genetic algorithms in search, optimization and machine learning. Addison Wesley, 1989 """ size = min(len(var1), len(var2)) # size = min(var1.size, var2.size) a, b = random.sample(xrange(size), 2) if a > b: a, b = b, a holes1, holes2 = [True] * size, [True] * size for i in range(size): if i < a or i > b: holes1[var2[i]] = False holes2[var1[i]] = False # We must keep the original values somewhere before scrambling everything temp1, temp2 = var1, var2 k1, k2 = b + 1, b + 1 for i in range(size): if not holes1[temp1[(i + b + 1) % size]]: var1[k1 % size] = temp1[(i + b + 1) % size] k1 += 1 if not holes2[temp2[(i + b + 1) % size]]: var2[k2 % size] = temp2[(i + b + 1) % size] k2 += 1 # Swap the content between a and b (included) for i in range(a, b + 1): var1[i], var2[i] = var2[i], var1[i] # var1[i], var2[i] = var2[i].copy(), var1[i].copy() return var1, var2