Andrea Schaerf

• University of Udine

We consider a recently proposed integrated healthcare problem that deals with the assignment of patients to suitable rooms in wards (Patient-to-Room) and the assignment of nurses to patients to balance their workload and reduce patient disturbance (Nurse-to-Patient), in one single stage. For this problem, we designed an integrated local search meth...

We consider a complex university timetabling problem arising in a four-year study program of teacher education where every student has to choose two subjects. Since any combination of two subjects is feasible, the goal of designing a collision-free timetable for every student seems to be unreachable. However, the task becomes more tractable because...

We consider the medical student scheduling (MSS) problem, which consists of assigning medical students to internships of different disciplines in various hospitals during the academic year to fulfill their educational and clinical training. The MSS problem takes into account, among other constraints and objectives, precedences between disciplines,...

We consider the Nurse Rostering problem, in the real-world formulation proposed by Curtois and Qu [8]. For this formulation, we propose a local search approach based on a combination of four neighborhoods guided by a Simulated Annealing metaheuristic, and we test it on the publicly available dataset. This research is still ongoing and the prelimina...

Purpose: Over time, the focus on supportive and geriatric care has shifted from being predominantly provided in institutional settings like nursing or rest homes to be delivered within the homes of the patients. Trained caregivers now provide home healthcare services by visiting patients in their own homes and carrying out specific services based o...

This study investigates the application of reinforcement learning for the adaptive tuning of neighborhood probabilities in stochastic multi-neighborhood search. The aim is to provide a more flexible and robust tuning method for heterogeneous scenarios than traditional offline tuning. We propose a novel mix of learning components for multi-neighborh...

We propose a multi-neighbourhood simulated annealing algorithm for the ITC-2007 version of the capacitated examination timetabling problem. The proposed solver is based on a combination of existing as well as newly proposed neighbourhoods that better exploit the disconnected structure of the underlying conflict graph and that explicitly deal with t...

We propose a portfolio of exact and metaheuristic methods for the rich examination timetabling problem introduced by Battistutta et al. (in: Hebrard, Musliu (eds) 17th International conference on the integration of constraint programming, artificial intelligence, and operations research (CPAIOR-2020), LNCS, vol 12296. Springer, Berlin, pp 69–81, 20...

We address the Permutation Flow-Shop Scheduling Problem with Predictive Maintenance presented by Varnier and Zerhouni (2012), that consists in finding the integrated schedule for production and maintenance tasks such that the total production time and the advance of maintenance services are minimized. Predictive maintenance services are scheduled b...

We study a novel version of the capacitated facility location problem, which includes incompatibilities among customers. For this problem, we propose and compare on a fair common ground a portfolio of metaheuristic techniques developed independently from each other. We tested our techniques on a new dataset composed of instances of increasing size,...

Crowdsourcing is the practice of outsourcing a task that would otherwise be performed by one or a few experts to a crowd of individuals. It is often used to collect large amounts of manually created labels that form datasets for training and evaluating supervised machine learning models. When designing a (micro-task) crowdsourcing experiment, it is...

We propose a survey of the research contributions on the field of Educational Timetabling with a specific focus on “standard” formulations and the corresponding benchmark instances. We identify six of such formulations and we discuss their features, pointing out their relevance and usability. Other available formulations and datasets are also revie...

We describe the solver that we developed for the Sports Timetabling Competition ITC2021, a three-stage simulated annealing approach, that makes use of a portfolio of six different neighborhoods. Five of these neighborhoods are taken from the literature on round-robin tournament scheduling, whereas the last one, denoted as PartialSwapTeamsPhased, is...

Solving a home energy management problem by Simulated Annealing.

We propose an algorithm selection approach and an instance space analysis for the well-known curriculum-based course timetabling problem (CB-CTT), which is an important problem for its application in higher education. Several state of the art algorithms exist, including both exact and metaheuristic methods. Results of these algorithms on existing i...

We propose a survey of the research contributions on the field of Educational Timetabling with a specific focus on "standard" formulations and the corresponding benchmark instances. We identify six of such formulations and we discuss their features, pointing out their relevance and usability. Other available formulations and datasets are also revie...

In this paper, we study an important real-life scheduling problem that can be formulated as an unrelated parallel machine scheduling problem with sequence-dependent setup times, due dates, and machine eligibility constraints. The objective is to minimise total tardiness and makespan. We adapt and extend a mathematical model to find optimal solution...

We consider the Minimum Interference Frequency Assignment Problem and we propose a novel Simulated Annealing approach that makes use of a portfolio of different neighborhoods, specifically designed for this problem. We undertake at once the two versions of the problem proposed by Correia (2001) and by Montemanni et al. (2001), respectively, and the...

The Test Laboratory Scheduling Problem (TLSP) is a real-world scheduling problem that extends the well-known Resource-Constrained Project Scheduling Problem (RCPSP) by several new constraints. Most importantly, the jobs have to be assembled out of several smaller tasks by the solver, before they can be scheduled. In this paper, we introduce differe...

We consider the energy scheduling problem for a domestic setting proposed and modeled by Della Croce et al. (Comput Ind Eng 109:169–178, 2017). We solve it by means of a Simulated Annealing approach based on a complex neighborhood structure. We perform an extensive and statistically-principled tuning phase using F-Race, given that the solver is dep...

We propose a Simulated Annealing approach for the Examination Timetabling problem, in the classical uncapacitated formulation of Carter et al. (1996). Our solver is based on a novel combination of many neighborhoods and a principled tuning procedure performed on artificial training instances. The experimental results on real-world benchmarks show t...

We investigate the examination timetabling problem in the context of Italian universities. The outcome is the definition of a general problem that can be applied to a large set of universities, but is quite different in many aspects from the classical versions proposed in the literature. We propose both a metaheuristic approach based on Simulated A...

This paper proposes a local search method based on a large neighborhood to solve the static version of the problem defined for the Second International Nurse Rostering Competition (INRC-II). The search method, driven by a simulated annealing metaheuristic, uses a combination of neighborhoods that either change the assignments of a nurse or swap the...

This paper reports on the Second International Nurse Rostering Competition (INRC-II). Its contributions are (1) a new problem formulation which, differently from INRC-I, is a multi-stage procedure, (2) a competition environment that, as in INRC-I, will continue to serve as a growing testbed for search approaches to the INRC-II problem, and (3) fina...

The thesis defense timetabling problem consists in composing the suitable committee for a set of defense sessions and assigning each graduation candidate to one of the sessions. In this work, we define the problem formulation that applies to some Italian universities and we provide three alternative solution methods, based on Integer Programming, C...

We propose a general model for the problem of planning and scheduling steelmaking and casting activities obtained by combining common features and constraints of the operations from a real plant and the literature. For tackling the problem, we develop a simulated annealing approach based on a solution space made of job permutations, which uses as s...

We consider the discrete single-machine, multi-item lot-sizing and scheduling problem and we propose a Simulated Annealing (SA) approach together with a statistically-principled tuning procedure to solve it. We compare our solver with the state-of-the-art methods based on Mixed Integer Programming (MIP), both on publicly-available instances and on...

We propose a simulated annealing approach for the examination timetabling problem, as formulated in the 2nd International Timetabling Competition. We apply a single-stage procedure in which infeasible solutions are included in the search space and dealt with using suitable penalties. Upon our approach, we perform a statistically-principled experime...

In this work, we consider the shift design problem and we define a novel, complex formulation arising from practical cases. In addition, we propose a new search method based on a fast Simulated Annealing, that, differently from previous approaches, solves the overall problem as a single-stage procedure. The core of the method is a composite neighbo...

MiniZinc is a high-level declarative modeling language that has become quite popular in the last few years. One of the main features of MiniZinc is the underlying middle-level constraint language FlatZinc, into which a MiniZinc model, along with a given instance, is translated. In this work, we describe an on-going project consisting in the impleme...

In this paper, we provide all information to participate to the Second International Nurse Rostering Competition (INRC-II). First, we describe the problem formulation, which, differently from INRC-I, is a multi-stage procedure. Second, we illustrate all the necessary infrastructure do be used together with the participant's solver, including the te...

We revisit and extend the patient admission scheduling problem, in order to make it suitable for practical applications. The main novelty is that we consider constraints on the utilisation of operating rooms for patients requiring a surgery. In addition, we propose a more elaborate model that includes a flexible planning horizon, a complex notion o...

We consider the university course timetabling problem, which is one of the most studied problems in educational timetabling. In particular, we focus our attention on the formulation known as curriculum-based course timetabling problem (CB-CTT), which has been tackled by many researchers and has many available benchmarks. The contributions of this p...

We propose an extension of the Generalized Balanced Academic Curriculum Problem (GBACP), a relevant planning problem arising in many universities. The problem consists of assigning courses to teaching terms and years, satisfying a set of precedence constraints and balancing students’ load among terms. Differently from the original GBACP formulation...

This paper is the organizers’ report on the Third International Timetabling Competition (ITC2011), run during 2011–2012 with the aim of raising the profile of automated high school timetabling. Its participants tackled 35 instances of the high school timetabling problem, taken from schools in 10 countries. The paper describes the data model used, t...

Shift design and break scheduling are important employee scheduling problems that arise in many contexts, especially at airports, call centers, and service industries. The aim is to find a minimum number of legal shifts, the number of workers assigned to them, and a suitable number of breaks so that the deviation from predetermined workforce requir...

is a logic-based executable specification language developed primarily by Marco Cadoli, with the collaboration of these and other authors. This paper describes, by means of several examples, the core language of , along with its semantics and expressive power. Finally, we briefly discuss the translation of specifications into SAT formulae, which pr...

Objective: Our goal is to propose and solve a new formulation of the recently-formalized patient admission scheduling problem, extending it by including several real-world features, such as the presence of emergency patients, uncertainty in the length of stay, and the possibility of delayed admissions. Method: We devised a metaheuristic approach...

We propose a set of formulations for the Curriculum-Based Course Timetabling problem, with the aim of “capturing” many real-world formulations, and thus encouraging researchers to “reduce” their specific problems to one of them, gaining the opportunity to compare and assess their results. This work is accompanied by a web application that maintains...

Portfolio selection is a problem arising in finance and economics. While its basic formulations can be efficiently solved using linear or quadratic programming, its more practical and realistic variants, which include various kinds of constraints and objectives, have in many cases to be tackled by heuristics. In this work, we present a hybrid techn...

We propose a multi-neighborhood local search procedure to solve a healthcare problem, known as the Patient Admission Scheduling problem. We design and experiment with different combinations of neighborhoods, showing that they have diverse effectiveness for different sets of weights of the cost components that constitute the objective function. We a...

The post-enrolment course timetabling (PE-CTT) is one of the most studied timetabling problems, for which many instances and results are available. In this work we design a metaheuristic approach based on Simulated Annealing to solve the PE-CTT. We consider all the different variants of the problem that have been proposed in the literature and we p...

The Balanced Academic Curriculum Problem (BACP) consists in assigning courses to teaching terms satisfying prerequisites and balancing the credit course load within each term. The BACP is part of the CSPLib with three benchmark instances, but its formulation is simpler than the problem solved in practice by universities. In this article, we introdu...

The Portfolio Selection Problem [7] is amongst the most studied issues in finance. In this problem, given a universe of assets (shares, options, bonds, . . . ), we are concerned in finding out a portfolio (i.e., which asset to invest in and by how much) which minimizes the risk while ensuring a given minimum return. In the most common formulation i...

We propose a hybrid local search algorithm for the solution of the Curriculum-Based Course Timetabling Problem and we undertake a systematic statistical study of the relative influence of the relevant features on the performances of the algorithm. In particular, we apply modern statistical techniques for the design and analysis of experiments, such...

Mr. Hamann gave some of the constraints upon the engineer in the automotive industry.

We propose a complex real-world problem in logistics that integrates routing and packing aspects. It can be seen as an extension of the Three-Dimensional Loading Capacitated Vehicle Routing Problem (3L-CVRP) introduced by Gendreau, Ion, Laporte, and Martello (2006). The 3L-CVRP consists in finding a set of routes that satisfies the demand of all cu...

In this work we formalize a new complex variant of the classical vehicle routing problem arising from a real-world application. Our formulation includes a heterogeneous fleet, a multi-day planning horizon, a complex carrier-dependent cost for vehicles, and the possibility of leaving orders unscheduled. For tackling this problem we propose a metaheu...

The problem of designing workforce shifts and break patterns is a relevant employee scheduling problem that arises in many contexts, especially in service industries. The issue is to find a minimum number of shifts, the number of workers assigned to them, and a suitable number of breaks so that the deviation from predetermined workforce requirement...

Nurse rostering is a complex task of practical relevance. Over the last years, researchers have been able to solve increasingly larger and more complex problems. In this paper, we describe the full procedure of running the First International Nurse Rostering Competition. The aim of the competition was to develop further interest in the area and to...

The 2nd International Timetabling Competition (ITC2007) was announced on the 1st Au-gust 2007. Building on the success of the first, this competition aimed to further develop interest in the area of educational timetabling while providing researchers with models of the problems faced which incorporate an increased number of real world constraints....

We consider a complex variant of the Container Loading Problem arising from a real-world industrial application. It includes several features such as multiple containers, box rotation, and bearable weight, which are of importance in many practical situations. In addition, it also considers the situation in which boxes have to be delivered to differ...

In this work we study a hybrid local search algorithm for the solu-tion of timetabling problems, and we undertake a systematic statistical study of the relative influence of the relevant features on the perfor-mances of the algorithm. In particular, we apply statistical methods for the design and analysis of experiments. This work is still ongoing,...

We propose a multi-neighborhood local search procedure to solve a healthcare problem, known as the Patient Admission problem. We design and experiment different combinations of neighborhoods, showing that they have diverse effectiveness for different sets of weights of the cost components that constitute the objective function. We also compute some...

The Balanced Academic Curriculum Problem (BACP) consists in assigning courses to teaching periods satisfying prerequisites and balancing students’ load. BACP is included in CSPlib along with three benchmark instances. However, the BACP formulation in CSPLib is actually simpler than the real problem that, in general, universities have to solve in pr...

The min-Shift Design problem (MSD) is an important scheduling problem that needs to be solved in many industrial contexts. The issue is to find a minimum number of shifts and the number of employees to be assigned to these shifts in order to minimize the deviation from workforce requirements. Our research considers both theoretical and practical a...

Portfolio selection is a relevant problem arising in finance and economics. While its basic formulations can be efficiently solved through linear or quadratic programming, its more practical and realistic variants, which include various kinds of constraints and objectives, have in many cases to be tackled by approximate algorithms. In this work, we...

During the execution of the project Floating Automotive Data Collection (FADC), various traffic conditions were recorded using in-vehicle measurements. A series of reference measurements were performed on a fixed route in Belgium in real traffic circumstances, including motorway, rural and city traffic. Three vehicles were used for the reference me...

The Traveling Tournament Problem (TTP) is a combinatorial problem that combines features from the traveling salesman problem and the tournament scheduling problem. We propose a family of tabu search solvers for the solution of TTP that make use of complex combination of many neighborhood structures. The different neighborhoods have been thoroughly...

Portfolio selection is a relevant problem arising in nance and economics. While its basic formulation can be ecien tly solved through linear programming, its more practical and realistic variants, that include various kinds of constraints and objec- tives, have to be tackled by approximate algorithms. In this work, we present a hybrid technique tha...

Following the success of the First International Timetabling Competition in 2002, the timetabling research community is organising a new competition on this problem (opening August 1st). This new competition will be on three dierent timetabling problems, and one of the tracks concerns the course timetabling formulation that applies to Italian unive...

One of the aspects of applying software engineering to Stochastic Local Search (SLS) is the principled analysis of the features of the problem instances and the behavior of SLS algorithms, which —because of their stochastic nature— might need sophisticated statistical tools. In this paper we describe EasyAnalyzer, an object-oriented framework for t...

We present a software tool, called EasySyn++, for the automatic synthesis of the source code for a set of stochastic local search (SLS) algorithms. EasySyn++ uses C++ as object language and relies on EasyLocal++, a C++ framework for the development of SLS algorithms. EasySyn++ is particularly suitable for the frequent case of having many neighborho...

In its early stage, tracking devices were primarily used to locate stolen vehicles. However functionalities can be expanded very far. Built-in functions can be added and extra sensor signals can be added to the standard registrations. Especially, fleet management solutions are envisaged currently. With the use of intelligent transport systems, serv...

EasyLocal++ is an object-oriented framework that helps the user to design and implement local search algorithms in C++ for a large variety of problems. In this paper we highlight the usability of EasyLocal++ by showing its contribution for the development of a solver for a real-life scheduling problem, namely the Course Timetabling problem. The Co...

In this paper, we first discuss the level of compliance for timetabling research to two important research qualities, namely measurability and reproducibility, analyzing what we believe are the most important contributions in the literature. Secondly, we discuss some practices that, in our opinion, could contribute to the improvement on the two afo...