Source code for qiskit_algorithms.optimizers.nlopts.isres

# This code is part of a Qiskit project.
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# (C) Copyright IBM 2018, 2023.
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# This code is licensed under the Apache License, Version 2.0. You may
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"""Improved Stochastic Ranking Evolution Strategy optimizer."""

from .nloptimizer import NLoptOptimizer, NLoptOptimizerType


class ISRES(NLoptOptimizer):
    """
    Improved Stochastic Ranking Evolution Strategy optimizer.

    Improved Stochastic Ranking Evolution Strategy (ISRES) is an algorithm for
    non-linearly constrained global optimization. It has heuristics to escape local optima,
    even though convergence to a global optima is not guaranteed. The evolution strategy is based
    on a combination of a mutation rule and differential variation. The fitness ranking is simply
    via the objective function for problems without nonlinear constraints. When nonlinear
    constraints are included, the `stochastic ranking proposed by Runarsson and Yao
    <https://notendur.hi.is/tpr/software/sres/Tec311r.pdf>`__
    is employed. This method supports arbitrary nonlinear inequality and equality constraints, in
    addition to the bound constraints.

    NLopt global optimizer, derivative-free.
    For further detail, please refer to
    http://nlopt.readthedocs.io/en/latest/NLopt_Algorithms/#isres-improved-stochastic-ranking-evolution-strategy
    """

    def get_nlopt_optimizer(self) -> NLoptOptimizerType:
        """Return NLopt optimizer type"""
        return NLoptOptimizerType.GN_ISRES