Source code for surrogate.sorting.sorNDHelperB

# 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 itemgetter

from .utils import isDominated, sweepB, splitB

def sorNDHelperB(best, worst, obj, front):
    """Assign front numbers to the solutions in H according to the solutions
    in L. The solutions in L are assumed to have correct front numbers and the
    solutions in H are not compared with each other, as this is supposed to
    happen after sorNDHelperB is called."""
    key = itemgetter(obj)
    if len(worst) == 0 or len(best) == 0:
        # One of the lists is empty: nothing to do
        return
    elif len(best) == 1 or len(worst) == 1:
        # One of the lists has one individual: compare directly
        for hi in worst:
            for li in best:
                if isDominated(hi[:obj + 1], li[:obj + 1]) or hi[:obj + 1] == li[:obj + 1]:
                    front[hi] = max(front[hi], front[li] + 1)
    elif obj == 1:
        sweepB(best, worst, front)
    elif key(min(best, key=key)) >= key(max(worst, key=key)):
        # All individuals from L dominate H for objective M:
        # Also supports the case where every individuals in L and H
        # has the same value for the current objective
        # Skip to objective M-1
        sorNDHelperB(best, worst, obj - 1, front)
    elif key(max(best, key=key)) >= key(min(worst, key=key)):
        best1, best2, worst1, worst2 = splitB(best, worst, obj)
        sorNDHelperB(best1, worst1, obj, front)
        sorNDHelperB(best1, worst2, obj - 1, front)
        sorNDHelperB(best2, worst2, obj, front)