Pareto Autonomous Local Search

This paper presents a study for the dynamic selection of operators in a local search process. The main purpose is to propose a generic autonomous local search method which manages operator selection from a set of available operators, built on neighborhood relations and neighbor selection functions, using the concept of Pareto dominance with respect to quality and diversity. The latter is measured using two different metrics. This control method is implemented using the Comet language in order to be easily introduced in various constraint local search algorithms. Focusing on permutation-based problems, experimental results are provided for the QAP and ATSP to assess the method’s effectiveness

The Random Quadratic Assignment Problem

Optimal assignment of classes to classrooms \cite{dickey}, design of DNA microarrays \cite{carvalho}, cross species gene analysis \cite{kolar}, creation of hospital layouts cite{elshafei}, and assignment of components to locations on circuit boards \cite{steinberg} are a few of the many problems which have been formulated as a quadratic assignment problem (QAP). Originally formulated in 1957, the QAP is one of the most difficult of all combinatorial optimization problems. Here, we use statistical mechanical methods to study the asymptotic behavior of problems in which the entries of at least one of the two matrices that specify the problem are chosen from a random distribution $P$. Surprisingly, this case has not been studied before using statistical methods despite the fact that the QAP was first proposed over 50 years ago \cite{Koopmans}. We find simple forms for $C_{\rm min}$ and $C_{\rm max}$, the costs of the minimal and maximum solutions respectively. Notable features of our results are the symmetry of the results for $C_{\rm min}$ and $C_{\rm max}$ and the dependence on $P$ only through its mean and standard deviation, independent of the details of $P$. After the asymptotic cost is determined for a given QAP problem, one can straightforwardly calculate the asymptotic cost of a QAP problem specified with a different random distribution $P$

Research trends in combinatorial optimization

Acknowledgments This work has been partially funded by the Spanish Ministry of Science, Innovation, and Universities through the project COGDRIVE (DPI2017-86915-C3-3-R). In this context, we would also like to thank the Karlsruhe Institute of Technology. Open access funding enabled and organized by Projekt DEAL.Peer reviewedPublisher PD

Hypervolume-Based Multi-Objective Path Relinking Algorithm

Abstract. This paper presents a hypervolume-based multi-objective path relinking algorithm for approximating the Pareto optimal set of multi-objective combinatorial optimization problems. We focus on integrating path relinking techniques within a multi-objective local search as an initialization function. Then, we carry out a range of experiments on bi-objective flow shop problem and bi-objective quadratic assignment problem. Experimental results and a statistical comparison are reported in the paper. In comparison with the other algorithms, one version of our proposed algorithm is very competitive. Some directions for future research are highlighted

Características morfométricas, rendimentos de carcaça, filé, vísceras e resíduos em tilápias-do-nilo em diferentes faixas de peso Morphometric characteristics, carcass, filet, viscera and residues in different weight categories of the Nile tilapia

Objetivou-se com este trabalho avaliar o efeito do peso sobre as relações das medidas de comprimento padrão de tilápias-do-nilo (Oreochromis niloticus). Avaliaram-se as medidas: comprimento da cabeça; altura do corpo, medida à frente do 1° raio das nadadeiras peitoral, dorsal, anal e caudal; largura do corpo, medida à frente da inserção do 1º raio das nadadeiras peitoral, dorsal e anal; perímetro, medido à frente da inserção do 1° raio das nadadeiras peitoral, dorsal e anal; e menor circunferência do pedúnculo; e os rendimentos de carcaça, filé, cabeça, nadadeira, pele, vísceras e resíduos. Foram utilizados 80 tilápias, em delineamento inteiramente casualizado com quatro tratamentos (faixas de peso 250 a 300 g; 350 a 400 g; 450 a 500 g, 550 a 600 g) e 20 repetições, considerando o peixe a unidade experimental. As menores variações nas características morfométricas foram observadas na faixa de peso de 450 a 600 g em comparação à faixa de 250 a 400 g. Nas faixas de peso 250 a 300 g, 350 a 400 g, 450 a 500 g e 550 a 600 g, não houve diferenças nos rendimentos de carcaça e filé e nas porcentagens de cabeça, nadadeira, pele e resíduos. A porcentagem de vísceras na faixa de peso 550 a 600 g (10,98%) foi significativamente inferior à obtida nas faixas de 250 a 300 g (12,77%), 350 a 400 g (13,26%) e 450 a 500 g (12,69%). O peso do filé na faixa de peso 350 a 400 g (260,50 g) foi superior ao da faixa de 250 a 300 g (239,95 g). Não houve diferença no peso do filé entre as faixas de peso 450 a 500 g (284,20 g) e 550 a 600 g (292,80 g). As faixas de peso de 450 a 500 g e 550 a 600 g apresentaram valores superiores de peso do filé em comparação às de 250 a 300 g e 350 a 400 g. Considerando o peso do filé, o peso ideal de abate da tilápia é de 450 a 500 g no intervalo de peso de 250 a 600 g.<br>The objective of this study was to evaluate the effect of weight categories on the relation of the measures of standard length; length of the head; height of the body measured at the front of the 1° ray of pectoral, dorsal, anal and tail fins; width of the body measured at the front of the insertion of 1º ray of pectoral, dorsal and anal fins; perimeter measured at the front of the insertion of the 1° ray of pectoral, dorsal and anal fins and minor circumference of the peduncle and yield of carcass, filet, head, fin, skin, viscera and residues of the Nile tilapia (Oreochromis niloticus). Eighty tilapia were used, in a completely randomized design, with four treatments (weight categories 250 the 300 g; 350 the 400 g; 450 the 500 g and 550 the 600 g) and 20 replications. Each fish was considered an experimental unit. The Nile tilapia presented minors variations in the morphometric characteristics in the weight category 450 to 600 g, when compared with the category 250 to 400 g. The weight category 250 the 300 g, 350 the 400 g, 450 the 500 g and 550 the 600 g provided the same yield of carcass, filet and percentages of head, fin, skin and residues. The percentage of viscera in the 550 the 600 g category (10.98%) was significantly lower when compared to 250 the 300 g (12.77%), 350 the 400 g (13.26%) and 450 the 500 g (12.69%). The weight of filet in the 350 the 400 g category (260.50 g) was higher than the 250 the 300 g category (239.95 g). There was no difference in the weight of fillet between the 450 the 500 g category (284.20 g) and 550 the 600 g (292.80 g). The category 450 the 500 g and 550 the 600 g presented higher values of weight of fillet when compared to 250 the 300 g and 350 the 400 g. According to the weight of fillet found, the ideal weight of slaughter of the tilapia is between 450 and 500 g in a range of 250-600 g