O problema dos árbitros viajantes: complexidade, modelagem e algoritmos

Estudamos neste doutorado o problema dos árbitros viajantes (TUP, do inglês traveling umpire problem), que consiste em um problema de otimizacão baseado no problema real de alocacão de árbitros às partidas da Liga Profissional de Beisebol dos Estados Unidos. O TUP recebe como entrada um torneio round robin duplo e tem como objetivo atribuir árbitros ás partidas deste torneio minimizando a distância total viajada por eles durante toda a competicão e respeitando restricões que impõem que cada árbitro não apite jogos de um mesmo time frequentemente e apite ao menos um jogo na sede de cada time. Demonstramos que o TUP é um problema NP-completo, fechando esta questão em relacão à sua complexidade que ficou em aberto durante sete anos. Também introduzimos duas novas formulacões matemáticas e uma heurística relax-and-fix para este problema. As análises de resultados computacionais comprovam que as formulacões matemáticas e a heurística relax-and-fix produzem limitantes inferiores e superiores de excelente qualidade para o TUP, melhorando diversos resultados da literatura.Sociedad Argentina de Informática e Investigación Operativa (SADIO

O problema dos árbitros viajantes: complexidade, modelagem e algoritmos

Estudamos neste doutorado o problema dos árbitros viajantes (TUP, do inglês traveling umpire problem), que consiste em um problema de otimizacão baseado no problema real de alocacão de árbitros às partidas da Liga Profissional de Beisebol dos Estados Unidos. O TUP recebe como entrada um torneio round robin duplo e tem como objetivo atribuir árbitros ás partidas deste torneio minimizando a distância total viajada por eles durante toda a competicão e respeitando restricões que impõem que cada árbitro não apite jogos de um mesmo time frequentemente e apite ao menos um jogo na sede de cada time. Demonstramos que o TUP é um problema NP-completo, fechando esta questão em relacão à sua complexidade que ficou em aberto durante sete anos. Também introduzimos duas novas formulacões matemáticas e uma heurística relax-and-fix para este problema. As análises de resultados computacionais comprovam que as formulacões matemáticas e a heurística relax-and-fix produzem limitantes inferiores e superiores de excelente qualidade para o TUP, melhorando diversos resultados da literatura.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Analysis of a Parallel Machine Scheduling Problem with Sequence Dependent Setup Times and Job Availability Intervals

In this study, we propose constraint programming (CP) model and logic-based Benders algorithms in order to make the best decisions for scheduling non-identical jobs with availability intervals and sequence dependent setup times on unrelated parallel machines in a fixed planning horizon. In this problem, each job has a profit, cost and must be assigned to at most one machine in such a way that total profit is maximized. In addition, the total cost has to be less than or equal to a budget level. Computational tests are performed on a real-life case study prepared in collaboration with the U.S. Army Corps of Engineers (USACE). Our initial investigations show that the pure CP model is very efficient in obtaining good quality feasible solutions but, fails to report the optimal solution for the majority of the problem instances. On the other hand, the two logic-based Benders decomposition algorithms are able to obtain near optimal solutions for 86 instances out of 90 examinees. For the remaining instances, they provide a feasible solution. Further investigations show the high quality of the solutions obtained by the pure CP model

Ship Routing with Pickup and Delivery for a Maritime Oil Transportation System: MIP Modeland Heuristics

This paper examines a ship routing problem with pickup and delivery and time windows for maritime oil transportation, motivated by the production and logistics activities of an oil company operating in the Brazilian coast. The transportation costs from offshore platforms to coastal terminals are an important issue in the search for operational excellence in the oil industry, involving operations that demand agile and effective decision support systems. This paper presents an optimization approach to address this problem, based on a mixed integer programming (MIP) model and a novel and exploratory application of two tailor-made MIP heuristics, based on relax-and-fix and time decomposition procedures. The model minimizes fuel costs of a heterogeneous fleet of oil tankers and costs related to freighting contracts. The model also considers company-specific constraints for offshore oil transportation. Computational experiments based on the mathematical models and the related MIP heuristics are presented for a set of real data provided by the company, which confirm the potential of optimization-based methods to find good solutions for problems of moderate sizes

O problema dos árbitros viajantes: complexidade, modelagem e algoritmos

Estudamos neste doutorado o problema dos árbitros viajantes (TUP, do inglês traveling umpire problem), que consiste em um problema de otimizacão baseado no problema real de alocacão de árbitros às partidas da Liga Profissional de Beisebol dos Estados Unidos. O TUP recebe como entrada um torneio round robin duplo e tem como objetivo atribuir árbitros ás partidas deste torneio minimizando a distância total viajada por eles durante toda a competicão e respeitando restricões que impõem que cada árbitro não apite jogos de um mesmo time frequentemente e apite ao menos um jogo na sede de cada time. Demonstramos que o TUP é um problema NP-completo, fechando esta questão em relacão à sua complexidade que ficou em aberto durante sete anos. Também introduzimos duas novas formulacões matemáticas e uma heurística relax-and-fix para este problema. As análises de resultados computacionais comprovam que as formulacões matemáticas e a heurística relax-and-fix produzem limitantes inferiores e superiores de excelente qualidade para o TUP, melhorando diversos resultados da literatura.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Operational Research: Methods and Applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes

Operational Research: Methods and Applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order

Operational research:methods and applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order