Source code for surrogate.selection.selTournament

# 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

from operator import attrgetter

from .selRandom import selRandom

def selTournament(individuals, k=1, tournsize=1):
    """Select *k* individuals from the input *individuals* using *k*
    tournaments of *tournsize* individuals. The list returned contains
    references to the input *individuals*.

    :param individuals: A list of individuals to select from.
    :param k: The number of individuals to select.
    :param tournsize: The number of individuals participating in each tournament.
    :returns: A list of selected individuals.

    This function uses the :func:`~random.choice` function from the python base
    :mod:`random` module.
    """
    chosen = []
    for i in xrange(k):
        aspirants = selRandom(individuals, tournsize)
        chosen.append(max(aspirants, key=attrgetter("fitness")))
    return chosen