Source code for

# Copyright 2022 Airbus SAS
# Copyright 2021 IRT Saint Exupéry,
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License version 3 as published by the Free Software Foundation.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
# Contributors:
#    INITIAL AUTHORS - initial API and implementation and/or initial
#                           documentation
#        :author: Gabriel Max DE MENDONÇA ABRANTES
"""Compromise points for multi-criteria decision-making."""

from __future__ import annotations

import logging
from typing import Any

from gemseo.algos.pareto import ParetoFront
from numpy import atleast_2d
from numpy import ndarray
from numpy import vstack
from pymoo.core.decomposition import Decomposition
from pymoo.decomposition.weighted_sum import WeightedSum

from import ScatterPareto

LOGGER = logging.getLogger(__name__)

[docs] class Compromise(ScatterPareto): """Scatter plot with pareto front and compromise points. See `Compromise Programming <>`_. """ fig_title = "Compromise Points" fig_name_prefix = "compromise" def _plot( self, decomposition: Decomposition | None = None, weights: ndarray | None = None, plot_extra: bool = True, plot_legend: bool = True, plot_arrow: bool = False, **scalar_options: Any, ) -> None: """Scatter plot of the pareto front along with the compromise points. The compromise points are calculated using a `scalarization function <>`_). Args: decomposition: The instance of the scalarization function to use. If ``None``, use a weighted sum. weights: The weights for the scalarization function. If None, a normalized array is used, e.g. [1./n, 1./n, ..., 1./n] for an optimization problem with n-objectives. plot_extra: Whether to plot the extra pareto related points, i.e. ``utopia``, ``nadir`` and ``anchor`` points. plot_legend: Whether to show the legend. plot_arrow: Whether to plot arrows connecting the utopia point to the compromise points. The arrows are annotated with the ``2-norm`` ( `Euclidian distance <>`_ ) of the vector represented by the arrow. **scalar_options: The keyword arguments for the scalarization function. Raises: TypeError: If the scalarization function is not an instance of ``Decomposition``. ValueError: If the number of weights does not match the number of objectives. """ if decomposition is None: decomposition = WeightedSum() elif not isinstance(decomposition, Decomposition): msg = ( "The scalarization function must be an instance of " "pymoo.core.Decomposition." ) raise TypeError(msg) # Objectives. n_obj = self.opt_problem.objective.dim # Default weights. if weights is None: weights = [1.0 / n_obj] * n_obj # Ensure correct dimension and type. weights = atleast_2d(weights).astype(float) # Check weight's dimension. if weights.shape[1] != n_obj: msg = "You must provide exactly one weight for each objective function!" raise ValueError(msg) # Create Pareto object. pareto = ParetoFront.from_optimization_problem(self.opt_problem) # Prepare points to plot. points = [] # Points' coordinates. point_labels = [] # Points' labels. for weight in weights: # Apply decomposition. d_res = pareto.f_optima, weight, utopian_point=pareto.f_utopia, nadir_point=pareto.f_anti_utopia, **scalar_options, ) # Best value according to the scalarization function. d_min = d_res.min() # Index where the minimum value is located (at the pareto front). d_idx = d_res.argmin() # Point's coordinates. points.append(pareto.f_optima[d_idx]) # Point's label. float_format = ".2e" if abs(d_min) > 1e3 else ".2f" point_labels.append(f"s({weight}) = {d_min:{float_format}}") # Concatenate points to plot. points = vstack(points) # Extra figure options. self.fig_title = f"{self.fig_title}\n(s = {decomposition.__class__.__name__})" # Update name's prefix with current decomposition function's name. self.fig_name_prefix += f"_{decomposition.__class__.__name__}" super()._plot(points, point_labels, plot_extra, plot_legend, plot_arrow)