Willy Oliveira | UFMS - Universidade Federal de Mato Grosso do Sul (original) (raw)

Papers by Willy Oliveira

Proceeding Series of the Brazilian Society of Computational and Applied Mathematics, 2017

Resumo. Neste artigo abordamos um problema de dimensionamento e sequenciamento de lotes de produç... more Resumo. Neste artigo abordamos um problema de dimensionamento e sequenciamento de lotes de produção em ambientes industriais com múltiplas linhas paralelas de produção que compartilham recursos comuns (por exemplo, máquinas e trabalhadores), onde para cada item existe um conjunto restrito de linhas capaz de produzí-lo. As limitações de recursos impedem a operação simultânea de todas as linhas em cada período do horizonte de planejamento, tornando-se necessário determinar, a cada período, quais as linhas que irão operar, consistindo assim num problema de designação que tem impacto direto no atendimento da demanda. Considera-se tempo e custo de preparação das linhas dependentes da sequência de produção. Neste trabalho um novo modelo matemático de programação inteira mistá e apresentado juntamente com testes computacionais a fim mostrar sua utilidade prática e apontar novas direções de pesquisa. Palavras-chave. Dimensionamento de lotes, Sequenciamento de produção, Programação inteira mista.

RAIRO - Operations Research, 2021

The purpose of this paper is to propose mathematical models to represent a lot sizing and schedul... more The purpose of this paper is to propose mathematical models to represent a lot sizing and scheduling problem on multiple production lines that share scarce resources and to investigate the computational performance of the proposed models. The main feature that differentiates this problem from others in the literature is that the decision on which lines to organize should be taken considering the availability of the necessary resources. The optimization criterion is the minimization of the costs incurred in the production process (inventory, backlogging, organization of production lines, and sequence-dependent setup costs). Nine mixed integer optimization models to represent the problem are given and, also, the results of an extensive computational study carried out using a set of instances from the literature. The computational study indicates that an efficient formulation, able to provide high quality solutions for large sized instances, can be obtained from a classical model by ma...

This paper addresses the Production Routing Problem (PRP). In this problem we make integrated dec... more This paper addresses the Production Routing Problem (PRP). In this problem we make integrated decisions about the number of products to be manufactured, the number of products to be delivered to each customer and the routes of the vehicles used to deliver the manufactured products. The integrated problem attempts to minimize both production and distribution costs, over all periods of a finite planning horizon. An Integer Programming Model is presented and model-based heuristics are proposed to tackle the PRP. Computational results are shown for both benchmark and proposed instances, in order to compare the proposed solution method with a highperformance commercial solver. The results show that our approach outperforms the commercial solver in getting high-quality solutions in instances with more than 10 customers and 5 products.

Pesquisa Operacional, 2021

In this paper, we propose a novel MIP-based heuristic method to deal with a lot sizing and schedu... more In this paper, we propose a novel MIP-based heuristic method to deal with a lot sizing and scheduling problem with multiple heterogeneous production lines in a production setting with perishable items. The problem is inspired by the production processes adopted by some Brazilian food industries and it considers that several production lines share the same scarce production resources. Therefore, only a subset of those lines can simultaneously operate in each production period. Moreover, the production environment is characterized by the existence of sequence-dependent setup times and costs, and by the production of perishable items which can be stocked for a short period only. Firstly, we propose a facility location reformulation for a model previously proposed in the literature. Secondly, we propose a heuristic composed of two phases. The first phase has an elaborated approach to building feasible solutions solving initially an aggregated lot sizing problem to decide which productio...

Revista Principia - Divulgação Científica e Tecnológica do IFPB, 2021

Neste artigo abordamos um problema de dimensionamento de lotes observado em algumas indústrias al... more Neste artigo abordamos um problema de dimensionamento de lotes observado em algumas indústrias alimentícias brasileiras que processam carnes embaladas. Nesse ambiente industrial, diversas linhas de produção compartilham os mesmos recursos produtivos (trabalhadores, ferramentas e máquinas) e devido à escassez desses recursos apenas um subconjunto das linhas pode operar em cada período. Além disso, as linhas são especializadas, de modo que, para cada produto existe uma única linha capaz de produzi-lo. Desse modo, a escolha das linhas de produção que irão operar impacta diretamente no conjunto de produtos que podem ser produzidos. Por fim, os itens produzidos são perecíveis, podendo permanecer estocados por um período limitado de tempo. Portanto, o problema estudado consiste em determinar, em cada período produtivo, quais linhas de produção devem ser montadas e o quanto se produzir de cada produto em cada linha, garantindo o atendimento das demandas dos clientes, evitando que os produt...

"O SENHOR é o meu pastor: nada me faltará. Deitar-me faz em verdes pastos, guia-me mansamente a á... more "O SENHOR é o meu pastor: nada me faltará. Deitar-me faz em verdes pastos, guia-me mansamente a águas tranquilas. Refrigera a minha alma; guia-me pelas veredas da justiça, por amor do seu nome." (Salmo 23-Bíblia Sagrada) Palavras-chave: Dimensionamento e sequenciamento de lotes, Programação matemática inteira mista, Heurísticas, Relaxação lagrangiana.

Pesquisa Operacional, 2019

This research addresses a lot sizing and scheduling problem inspired by a real-world production e... more This research addresses a lot sizing and scheduling problem inspired by a real-world production environment where the customers make advanced orders and the industry need to decide which orders will be accepted with the aim of maximizing the profit respecting the production capacity constraints. Orders are composed of different types of items which must be delivered within a given time interval and, moreover, such orders cannot be split. A mixed integer programming (MIP) model is proposed to represent the problem and a MIP-based heuristic is also proposed to deliver good solutions at an acceptable computational time. The heuristic is composed of three phases (construction, deterministic improvement and stochastic improvement phases) and combines relax-and-fix, fix-and-optimize, and iterative MIP based neighborhood search procedures. Computational tests are presented in order to study the efficiency of the proposed approaches.

Journal of the Operational Research Society, 2019

This paper addresses a lot sizing and scheduling problem inspired from a real-world production en... more This paper addresses a lot sizing and scheduling problem inspired from a real-world production environment apparent in food industry. Due to the scarcity of resources, only a subset of production lines can operate simultaneously, and those lines need to be assembled in each production period. In addition, the products are perishable, and there are often significant sequence-dependent setup times and costs. We first propose a standard mixed integer programming model for the problem, and then a reformulation of the standard model in order to allow us to define a branching rule to accelerate the performance of the branch-and-bound algorithm. We also propose an efficient relax-and-fix procedure that can provide high-quality feasible solutions and competitive dual bounds for the problem. Computational experiments indicate that our approaches provide superior results when benchmarked with a commercial solver and an established relax-and-fix heuristic from the literature.

TEMA (São Carlos), 2018

In this paper, we deal with the Capacitated Lot Sizing and Scheduling Problem with sequencedepend... more In this paper, we deal with the Capacitated Lot Sizing and Scheduling Problem with sequencedependent setup times and costs - CLSD model. More specifically, we propose a simple reformulation for the CLSD model that enables us to define a new branching rule to be used in Branch-and-Bound (or Branch-and-Cut) algorithms to solve this NP-hard problem. Our branching rule can be easily implemented in commercial solvers. Computational tests performed in 240 test instances from the literature show that our approach can significantly reduce the running time to solve this problem using a Branch-and-Cut algorithm of a commercial MIP solver.Therefore, our approach can also improve the performance of other approaches that need to solve partial sub problems of the CLSD model in each iteration, such as Lagrangian approaches and heuristics based on the mathematical formulation of the problem.

Proceeding Series of the Brazilian Society of Computational and Applied Mathematics, 2018

Resumo. Este artigo lida com um problema de dimensionamento e sequenciamento de lotes de produção... more Resumo. Este artigo lida com um problema de dimensionamento e sequenciamento de lotes de produção em ambientes industriais onde múltiplas linhas de produção compartilham recursos comuns. Devidoà escassez desses recursos, as linhas não podem ser todas ativadas simultâneamente, tornando-se necessário determinar, a cada período, quais linhas de produção serão ativadas. O ambiente produtivo estudado também se caracteriza pela existência de custos e tempos de preparação para produção dependentes da sequência. Um modelo de otimização inteira mista para representação do problemaé apresentado, bem como, heurísticas baseadas na formulação matemática do problema. Testes computacionais são realizados comparando o desempenho das heurísticas propostas neste trabalho e mostram que estes métodos têm melhor desempenho do que um resolvedor comercial. Palavras-chave. MIP heurísticas, Dimensionamento e sequenciamento de lotes, Recusos escassos.