Source code for surrogate.crossover.cxTwoPoint

# 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.
# You may obtain a copy of the License at
# 
#    http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Author: Quan Pan <quanpan302@hotmail.com>
# License: Apache License, Version 2.0
# Create: 2016-12-02

import random

def cxTwoPoint(var1, var2):
    """Executes a two-point crossover on the input :term:`sequence`
    individuals. The two individuals are modified in place and both keep
    their original length.

    :param var1: The first variable participating in the crossover.
    :param var2: The second variable participating in the crossover.
    :returns: A tuple of two variables.

    This function uses the :func:`~random.randint` function from the Python
    base :mod:`random` module.
    """
    size = min(len(var1), len(var2))
    # size = min(var1.size, var2.size)
    cxpoint1 = random.randint(1, size)
    cxpoint2 = random.randint(1, size - 1)
    if cxpoint2 >= cxpoint1:
        cxpoint2 += 1
    else:  # Swap the two cx points
        cxpoint1, cxpoint2 = cxpoint2, cxpoint1

    var1[cxpoint1:cxpoint2], var2[cxpoint1:cxpoint2] = var2[cxpoint1:cxpoint2], var1[cxpoint1:cxpoint2]
    # var1[cxpoint1:cxpoint2], var2[cxpoint1:cxpoint2] = var2[cxpoint1:cxpoint2].copy(), var1[cxpoint1:cxpoint2].copy()

    return var1, var2