Source code for surrogate.mutation.mutUniformInt

# 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
from collections import Sequence
from itertools import repeat

def mutUniformInt(variable, low=0.0, up=1.0, prob=0.5):
    """Mutate an individual by replacing attributes, with probability *prob*,
    by a integer uniformly drawn between *low* and *up* inclusively.

    :param variable: :term:`Sequence <sequence>` Decision Variable to be mutated.
    :param low: The lower bound or a :term:`python:sequence` of
                of lower bounds of the range from wich to draw the new
                integer.
    :param up: The upper bound or a :term:`python:sequence` of
               of upper bounds of the range from wich to draw the new
               integer.
    :param prob: Independent probability for each attribute to be mutated.
    :returns: A tuple of one variable.
    """
    size = len(variable)
    # size = variable.size
    if not isinstance(low, Sequence):
        low = repeat(low, size)
    elif len(low) < size:
        raise IndexError("low must be at least the size of variable: %d < %d" % (len(low), size))
    if not isinstance(up, Sequence):
        up = repeat(up, size)
    elif len(up) < size:
        raise IndexError("up must be at least the size of variable: %d < %d" % (len(up), size))

    for i, xl, xu in zip(xrange(size), low, up):
        if random.random() < prob:
            variable[i] = random.randint(xl, xu)

    return variable