407 research outputs found
On the Combined Impact of Population Size and Sub-problem Selection in MOEA/D
This paper intends to understand and to improve the working principle of
decomposition-based multi-objective evolutionary algorithms. We review the
design of the well-established Moea/d framework to support the smooth
integration of different strategies for sub-problem selection, while
emphasizing the role of the population size and of the number of offspring
created at each generation. By conducting a comprehensive empirical analysis on
a wide range of multi-and many-objective combinatorial NK landscapes, we
provide new insights into the combined effect of those parameters on the
anytime performance of the underlying search process. In particular, we show
that even a simple random strategy selecting sub-problems at random outperforms
existing sophisticated strategies. We also study the sensitivity of such
strategies with respect to the ruggedness and the objective space dimension of
the target problem.Comment: European Conference on Evolutionary Computation in Combinatorial
Optimization, Apr 2020, Seville, Spai
A convergence and diversity guided leader selection strategy for many-objective particle swarm optimization
Recently, particle swarm optimizer (PSO) is extended to solve many-objective optimization problems (MaOPs) and becomes a hot research topic in the field of evolutionary computation. Particularly, the leader particle selection (LPS) and the search direction used in a velocity update strategy are two crucial factors in PSOs. However, the LPS strategies for most existing PSOs are not so efficient in high-dimensional objective space, mainly due to the lack of convergence pressure or loss of diversity. In order to address these two issues and improve the performance of PSO in high-dimensional objective space, this paper proposes a convergence and diversity guided leader selection strategy for PSO, denoted as CDLS, in which different leader particles are adaptively selected for each particle based on its corresponding situation of convergence and diversity. In this way, a good tradeoff between the convergence and diversity can be achieved by CDLS. To verify the effectiveness of CDLS, it is embedded into the PSO search process of three well-known PSOs. Furthermore, a new variant of PSO combining with the CDLS strategy, namely PSO/CDLS, is also presented. The experimental results validate the superiority of our proposed CDLS strategy and the effectiveness of PSO/CDLS, when solving numerous MaOPs with regular and irregular Pareto fronts (PFs)
Multi-Objective Archiving
Most multi-objective optimisation algorithms maintain an archive explicitly
or implicitly during their search. Such an archive can be solely used to store
high-quality solutions presented to the decision maker, but in many cases may
participate in the search process (e.g., as the population in evolutionary
computation). Over the last two decades, archiving, the process of comparing
new solutions with previous ones and deciding how to update the
archive/population, stands as an important issue in evolutionary
multi-objective optimisation (EMO). This is evidenced by constant efforts from
the community on developing various effective archiving methods, ranging from
conventional Pareto-based methods to more recent indicator-based and
decomposition-based ones. However, the focus of these efforts is on empirical
performance comparison in terms of specific quality indicators; there is lack
of systematic study of archiving methods from a general theoretical
perspective. In this paper, we attempt to conduct a systematic overview of
multi-objective archiving, in the hope of paving the way to understand
archiving algorithms from a holistic perspective of theory and practice, and
more importantly providing a guidance on how to design theoretically desirable
and practically useful archiving algorithms. In doing so, we also present that
archiving algorithms based on weakly Pareto compliant indicators (e.g.,
epsilon-indicator), as long as designed properly, can achieve the same
theoretical desirables as archivers based on Pareto compliant indicators (e.g.,
hypervolume indicator). Such desirables include the property limit-optimal, the
limit form of the possible optimal property that a bounded archiving algorithm
can have with respect to the most general form of superiority between solution
sets.Comment: 21 pages, 4 figures, journa
Hybridization of Decomposition and Local Search for Multiobjective Optimization
Combining ideas from evolutionary algorithms, decomposition approaches, and Pareto local search, this paper suggests a simple yet efficient memetic algorithm for combinatorial multiobjective optimization problems: memetic algorithm based on decomposition (MOMAD). It decomposes a combinatorial multiobjective problem into a number of single objective optimization problems using an aggregation method. MOMAD evolves three populations: 1) population PLfor recording the current solution to each subproblem; 2) population PPfor storing starting solutions for Pareto local search; and 3) an external population PEfor maintaining all the nondominated solutions found so far during the search. A problem-specific single objective heuristic can be applied to these subproblems to initialize the three populations. At each generation, a Pareto local search method is first applied to search a neighborhood of each solution in PPto update PLand PE. Then a single objective local search is applied to each perturbed solution in PLfor improving PLand PE, and reinitializing PP. The procedure is repeated until a stopping condition is met. MOMAD provides a generic hybrid multiobjective algorithmic framework in which problem specific knowledge, well developed single objective local search and heuristics and Pareto local search methods can be hybridized. It is a population based iterative method and thus an anytime algorithm. Extensive experiments have been conducted in this paper to study MOMAD and compare it with some other state-of-the-art algorithms on the multiobjective traveling salesman problem and the multiobjective knapsack problem. The experimental results show that our proposed algorithm outperforms or performs similarly to the best so far heuristics on these two problems
Multiobjective evolutionary algorithm based on vector angle neighborhood
Selection is a major driving force behind evolution and is a key feature of multiobjective evolutionary algorithms. Selection aims at promoting the survival and reproduction of individuals that are most fitted to a given environment. In the presence of multiple objectives, major challenges faced by this operator come from the need to address both the population convergence and diversity, which are conflicting to a certain extent. This paper proposes a new selection scheme for evolutionary multiobjective optimization. Its distinctive feature is a similarity measure for estimating the population diversity, which is based on the angle between the objective vectors. The smaller the angle, the more similar individuals. The concept of similarity is exploited during the mating by defining the neighborhood and the replacement by determining the most crowded region where the worst individual is identified. The latter is performed on the basis of a convergence measure that plays a major role in guiding the population towards the Pareto optimal front. The proposed algorithm is intended to exploit strengths of decomposition-based approaches in promoting diversity among the population while reducing the user's burden of specifying weight vectors before the search. The proposed approach is validated by computational experiments with state-of-the-art algorithms on problems with different characteristics. The obtained results indicate a highly competitive performance of the proposed approach. Significant advantages are revealed when dealing with problems posing substantial difficulties in keeping diversity, including many-objective problems. The relevance of the suggested similarity and convergence measures are shown. The validity of the approach is also demonstrated on engineering problems.This work was supported by the Portuguese Fundacao para a Ciencia e Tecnologia under grant PEst-C/CTM/LA0025/2013 (Projecto Estrategico - LA 25 - 2013-2014 - Strategic Project - LA 25 - 2013-2014).info:eu-repo/semantics/publishedVersio
A decomposition-based multiobjective evolutionary algorithm with angle-based adaptive penalty
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.A multiobjective evolutionary algorithm based on decomposition (MOEA/D) decomposes a multiobjective optimization problem (MOP) into a number of scalar optimization subproblems and optimizes them in a collaborative manner. In MOEA/D, decomposition mechanisms are used to push the population to approach the Pareto optimal front (POF), while a set of uniformly distributed weight vectors are applied to maintain the diversity of the population. Penalty-based boundary intersection (PBI) is one of the approaches used frequently in decomposition. In PBI, the penalty factor plays a crucial role in balancing convergence and diversity. However, the traditional PBI approach adopts a fixed penalty value, which will significantly degrade the performance of MOEA/D on some MOPs with complicated POFs. This paper proposes an angle-based adaptive penalty (AAP) scheme for MOEA/D, called MOEA/D-AAP, which can dynamically adjust the penalty value for each weight vector during the evolutionary process. Six newly designed benchmark MOPs and an MOP in the wastewater treatment process are used to test the effectiveness of the proposed MOEA/D-AAP. Comparison experiments demonstrate that the AAP scheme can significantly improve the performance of MOEA/D
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