Tony Wauters

Tony Wauters
KU Leuven | ku leuven · Department of Computer Science

PhD

About

48
Publications
12,032
Reads
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693
Citations
Introduction
Currently working on: - Traveling Umpire Problem - Automated storage and retrieval systems - 3D Container loading - Port logistic optimization
Additional affiliations
October 2015 - present
KU Leuven
Position
  • Professor (Assistant)
December 2012 - September 2015
KU Leuven
Position
  • PostDoc Position

Publications

Publications (48)
Article
This paper addresses the two-dimensional bin packing problem with guillotine constraints. The problem requires a set of rectangular items to be cut from larger rectangles, known as bins, while only making use of edge-to-edge (guillotine) cuts. The goal is to minimize the total bin area needed to cut all required items. This paper also addresses var...
Article
We present a fast algorithm to solve nesting problems based on a semi-discrete representation of both the 2D non-convex pieces and the strip. The pieces and the strip are represented by a set of equidistant vertical line segments. The discretization algorithm uses a sweep-line method and applies minimal extensions to the line segments of a piece to...
Article
The two-echelon location routing problem (2E-LRP) arises in freight distribution when goods available at different origins are delivered to their respective destinations via intermediate facilities. The literature concerning the 2E-LRP considers freight capacities of vehicles to be scalars, while customer demands are additive volumes of individual...
Chapter
Neighborhood enumeration is a fundamental concept in the design of local search-based metaheuristics. It is often the only principle of intensification present in a metaheuristic and serves as the basis for various metaheuristics. Given its importance, it is surprising that academic reporting on enumeration strategies lacks the necessary informatio...
Article
Full-text available
The shift minimization personnel task scheduling problem is an NP-complete optimization problem that concerns the assignment of tasks to multi-skilled employees with a view to minimize the total number of assigned employees. Recent literature indicates that hybrid methods which combine exact and heuristic techniques such as matheuristics are effici...
Article
In the problem of extracting maximal items/objects from three-dimensional materials, we are given a piece of solid material and an object with predefined ratios. The goal is to extract the largest possible convex or non-convex object from the solid material. There are two variants of the problem: the general case where the solid material is non-con...
Preprint
In this article, a novel approach to solve combinatorial optimization problems is proposed. This approach makes use of a heuristic algorithm to explore the search space tree of a problem instance. The algorithm is based on Monte Carlo tree search, a popular algorithm in game playing that is used to explore game trees. By leveraging the combinatoria...
Conference Paper
The vertex colouring problem is one of the most widely studied and popular problems in graph theory. In light of the recent interest in hybrid methods involving mathematical programming, this paper presents an attempt to design a matheuristic approach for the problem. A decomposition-based approach is introduced which utilizes an integer programmin...
Conference Paper
Full-text available
This work introduces a multithreaded solving methodology for local search based metaheuristics. It runs a single local search that spreads move evaluations across multiple threads. To preserve incremental score calculation (delta evaluation) capabilities, which are essential for the performance of local search methods, the child threads reproduce t...
Article
Prisoners often require transportation to and from services such as hospital appointments, court proceedings and family visits during their imprisonment. Organising daily prisoners transportation consumes a huge amount of resources. A large fleet of highly protected vehicles, their drivers and security guards must be assigned to all prisoner transp...
Article
The Three-dimensional Single Large Object Placement Problem consists of a set of weakly heterogeneous items that must be placed inside a single larger object without overlapping each other. Many constraints can be considered depending on the practical specifications of the problem being solved, such as orientation, stability, weight limit and posit...
Article
Congested traffic networks impose great difficulties upon scheduling material transportation in industrial settings. Dispatching decisions become complex when, in addition to conflict-free routes, storage location must also be considered. The present paper integrates the dispatch and conflict-free routing of capacitated vehicles with the storage al...
Article
Three-dimensional Cutting and Packing Problems consist of a set of items that must be placed inside one or more larger items (containers). Such problems enforce non-overlapping constraints which ensure that the smaller items being assigned must completely fit inside their respective container. Despite extensive preexisting literature, there is the...
Article
The Traveling Umpire Problem (TUP) is a combinatorial optimization problem concerning the assignment of umpires to the games of a fixed double round-robin tournament. The TUP draws inspiration from the real world multi-objective Major League Baseball (MLB) umpire scheduling problem, but is, however, restricted to the single objective of minimizing...
Article
Full-text available
We investigate a structural decomposition for the capacitated vehicle routing problem (CVRP) based on vehicle-to-customer "assignment" and visits "sequencing" decision variables. We show that an heuristic search focused on assignment decisions with a systematic optimal choice of sequences (using Concorde TSP solver) during each move evaluation is p...
Article
The present paper considers a hybrid local search approach to the Eternity II puzzle and to unsigned, rectangular, edge matching puzzles in general. Both an original mixed-integer linear programming (MILP) formulation and a novel Max-Clique formulation are presented for this NP-hard problem. Although the presented formulations remain computationall...
Article
This work presents the stochastic local search method for the Swap-Body Vehicle Routing Problem (SB-VRP) that won the First VeRoLog Solver Challenge. The SB-VRP, proposed on the occasion of the challenge, is a generalization of the classical Vehicle Routing Problem (VRP) in which customers are served by vehicles whose sizes may be enlarged via the...
Article
Automated Storage and Retrieval Systems (AS/RS) have become vital in today’s distribution and production environments, however it remains necessary to equip them with more efficient operational control policies. Motivated by real situations encountered by companies employing AS/RS, the present paper studies a miniload AS/RS system, with a dual shut...
Article
Full-text available
This article presents a review of the use of optimisation models for pedestrian evacuation and design problems. The articles are classified according to the problem type that is studied, the level of model realism, and the modelling or solution technique. To substantiate the classification criteria and to provide a background for the reader, releva...
Article
The traditional set of manufacturing scheduling problems concern general and easy-to-measure economic objectives such as makespan and tardiness. The variable nature of energy costs over the course of the day remains mostly ignored by most previous research. This variability should not be considered an added complexity, but rather an opportunity for...
Article
Efficient container loading has the potential to considerably reduce logistics and transportation costs. The container loading problem is computationally complex and, despite extensive academic effort, there remains room for algorithm improvement. Real-world problems are not always addressed satisfactorily primarily due to the large number of compl...
Conference Paper
Methods based on Stochastic Local Search (SLS) have been ranked as the best heuristics available for many hard combinatorial optimization problems. The design of SLS methods which use many neighborhoods poses difficult questions regarding the exploration of these neighborhoods: how much computational effort should be invested in each neighborhood?...
Article
The Traveling Umpire Problem (TUP) is an optimization problem in which umpires have to be assigned to games in a double round robin tournament. The objective is to obtain a solution with minimum total travel distance over all umpires, while respecting hard constraints on assignments and sequences. Up till now, no general nor dedicated algorithm was...
Article
Full-text available
The present paper introduces a learning-based optimization approach to the resource-constrained multi-project scheduling problem. Multiple projects, each with their own set of activities, need to be scheduled. The objectives dealt with here include minimization of the average project delay and total makespan. The availability of local and global re...
Article
Full-text available
Scheduling projects is a difficult and time consuming process, and has far-reaching implications for any organization’s operations. By generalizing various aspects of project scheduling, decision makers are enabled to capture reality and act accordingly. In the context of the MISTA 2013 conference, the first MISTA challenge, organized by the author...
Conference Paper
Full-text available
In this abstract we present methods for solving a real world task schedul-ing problem, in the automotive maintenance sector. Tasks have to be assigned to personnel taking into account their skills, available working periods and other constraints. We present a model for this complex and highly constrained schedul-ing problem, and an approach for sol...
Article
The Traveling Umpire Problem (TUP) is a challenging combinatorial optimization problem based on scheduling umpires for Major League Baseball. The TUP aims at assigning umpire crews to the games of a fixed tournament, minimizing the travel distance of the umpires. The present paper introduces two complementary heuristic solution approaches for the T...
Article
From an operational point of view, Ready-Mixed Concrete Suppliers are faced with challenging operational problems such as the acquisition of raw materials, scheduling of production facilities, and the transportation of concrete. This paper is centered around the logistical and distributional part of the operation: the scheduling and routing of conc...
Article
Assigning scheduled tasks to a multi-skilled workforce is a known NP-complete problem with many applications in health care, services, logistics and manufacturing. Optimising the use and composition of costly and scarce resources such as staff has major implications on any organisation's health. The present paper introduces a new, versatile two-pha...
Article
The paper presents a new generalization of the one-dimensional cutting stock problem (1D-CSP) that considers cut losses dependent on the items' cutting sequence. It is shown that this generalization can still be solved approximately by standard 1D-CSP approaches. Furthermore, a pattern-based heuristic (denoted by HSD) is presented that specifically...
Article
Strip packing intends to minimise the height required for placing a set of rectangular items into a strip with infinite height. The present paper introduces a fast, yet effective shaking algorithm for the two- and three-dimensional strip packing problems, which are both NP-hard. The proposed heuristic procedure starts from an ordered item list, fro...
Article
Full-text available
Many techniques that boost the speed or quality of metaheuristic search have been reported within literature. The present contribution investigates the rather rare combination of reinforcement learning and metaheuristics. Reinforcement learning techniques describe how an autonomous agent can learn from experience. Previous work has shown that a net...
Article
Full-text available
The present paper considers the optimisation version of the Eternity II puzzle problem and unsigned edge matching puzzles in general. The goal of this optimisation problem is to maximise the number of matching edges in the puzzle. In 2010, the META Eternity II contest awarded the best performing metaheuristic approach to this hard combinatorial opt...
Article
The present paper offers an integrated approach to real-world production scheduling for the food processing industries. A manufacturing execution system is very appropriate to monitor and control the activities on the shop floor. Therefore, a specialized scheduler, which is the focus of this paper, has been developed to run at the core of such a sy...
Conference Paper
Permutations occur in a great variety of optimization problems, such as routing, scheduling and assignment problems. The present paper introduces the use of learning automata for the online learning of good quality permutations. Several centralized and decentralized methods using individual and common rewards are presented. The performance, memory...
Article
Full-text available
Intelligent optimization refers to the promising technique of integrating learning mechanisms into (meta-) heuristic search. In this paper, we use multi-agent reinforcement learning for building high-quality solutions for the multi-mode resource-constrained project scheduling problem (MRCPSP). We use a network of distributed reinforcement learning...
Article
In cooperation with MESware nv1 the authors have developed an adaptive and generic production scheduling system capable of handling complex real world constraints. While scheduling multiple customer orders, the scheduler can handle complex resource and time constraints. Examples include: different types of plant layouts, sequence-dependent setup ti...
Conference Paper
Full-text available
In this paper we demonstrate how decentralized multi-project scheduling problems can be solved efficiently by a group of project manager agents playing a simple sequence learning game. In the multi-project scheduling problem, multiple projects, each having a number of activities, must be scheduled. A set of local and global resources are available...
Article
Full-text available
This abstract introduces a novel approach to intelligently select appropriate modes for each activity in the multi mode resource constrained project scheduling problem. The mode of an activity deter- mines its duration and the resources that it requires. In order to obtain a good (or optimal) makespan, nding an appropriate mode for each activity is...
Article
Full-text available
This paper introduces a novel approach for solving the multi-mode resource-constrained project scheduling problem (MR-CPSP), in which multiple execution modes are available for each of the activities of the project. The new approach ap-plies simple agent learning devices, i.e. learning automata, to construct the project schedules. We present some c...
Article
Full-text available
In this paper we propose a new hyper-heuristic that is composed of a simple selection mecha-nism based on a learning automaton and a new acceptance mechanism, i.e. the Iteration Limited Threshold Accepting criterion. This hyper-heuristic is applied to the challenging Traveling Tour-nament Problem. We show that the new hyper-heuristic method consist...
Article
In this paper we demonstrate how decentralized multi-project scheduling problems can be solved eciently by a group of project manager agents playing a simple sequence learning game. In the multi-project scheduling problem, multiple projects, each having a number of activities, must be sche- duled. A set of local and global resources are available f...

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