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Tournament selection dominated

This file is part of the TPOT library.

The current version of TPOT was developed at Cedars-Sinai by: - Pedro Henrique Ribeiro (https://github.com/perib, https://www.linkedin.com/in/pedro-ribeiro/) - Anil Saini (anil.saini@cshs.org) - Jose Hernandez (jgh9094@gmail.com) - Jay Moran (jay.moran@cshs.org) - Nicholas Matsumoto (nicholas.matsumoto@cshs.org) - Hyunjun Choi (hyunjun.choi@cshs.org) - Miguel E. Hernandez (miguel.e.hernandez@cshs.org) - Jason Moore (moorejh28@gmail.com)

The original version of TPOT was primarily developed at the University of Pennsylvania by: - Randal S. Olson (rso@randalolson.com) - Weixuan Fu (weixuanf@upenn.edu) - Daniel Angell (dpa34@drexel.edu) - Jason Moore (moorejh28@gmail.com) - and many more generous open-source contributors

TPOT is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

TPOT is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with TPOT. If not, see http://www.gnu.org/licenses/.

tournament_selection_dominated(scores, k, n_parents=2, rng=None)

Select the best individual among 2 randomly chosen individuals, k times. Selection is first attempted by checking if one individual dominates the other. Otherwise one with the highest crowding distance is selected. The returned list contains the indices of the chosen individuals.

Parameters:

Name Type Description Default
scores ndarray

The score matrix, where rows the individuals and the columns are the corresponds to scores on different objectives.

 required
k int

The number of individuals to select.

 required
n_parents int

The number of parents to select per individual. The default is 2.

 2
rng (int, Generator)

The random number generator. The default is None.

 None

Returns:

Type Description
A array of indices of selected individuals of shape (k, n_parents).
Source code in tpot2/selectors/tournament_selection_dominated.py 
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def tournament_selection_dominated(scores, k, n_parents=2, rng=None):
    """
    Select the best individual among 2 randomly chosen
    individuals, *k* times. Selection is first attempted by checking if one individual dominates the other. Otherwise one with the highest crowding distance is selected.
    The returned list contains the indices of the chosen *individuals*.

    Parameters
    ----------
    scores : np.ndarray
        The score matrix, where rows the individuals and the columns are the corresponds to scores on different objectives.
    k : int
        The number of individuals to select.
    n_parents : int, optional
        The number of parents to select per individual. The default is 2.
    rng : int, np.random.Generator, optional
        The random number generator. The default is None.

    Returns
    -------
        A array of indices of selected individuals of shape (k, n_parents).

    """

    rng = np.random.default_rng(rng)
    pareto_fronts = nondominated_sorting(scores)

    # chosen = list(itertools.chain.from_iterable(fronts))
    # if len(chosen) >= k:
    #     return chosen[0:k]

    crowding_dict = {}
    chosen = []
    current_front_number = 0
    while current_front_number < len(pareto_fronts):

        current_front = np.array(list(pareto_fronts[current_front_number]))
        front_scores = [scores[i] for i in current_front]
        crowding_distances = crowding_distance(front_scores)
        for i, crowding in zip(current_front,crowding_distances):
            crowding_dict[i] = crowding

        current_front_number += 1


    chosen = []
    for i in range(k*n_parents):
        asp1 = rng.choice(len(scores))
        asp2 = rng.choice(len(scores))

        if dominates(scores[asp1], scores[asp2]):
            chosen.append(asp1)
        elif dominates(scores[asp2], scores[asp1]):
            chosen.append(asp2)

        elif crowding_dict[asp1] > crowding_dict[asp2]:
            chosen.append(asp1)
        elif crowding_dict[asp1] < crowding_dict[asp2]:
            chosen.append(asp2)

        else:
            chosen.append(rng.choice([asp1,asp2]))

    return np.reshape(chosen, (k, n_parents))