27 research outputs found
A Multistage Stochastic Programming Approach to the Dynamic and Stochastic VRPTW - Extended version
We consider a dynamic vehicle routing problem with time windows and
stochastic customers (DS-VRPTW), such that customers may request for services
as vehicles have already started their tours. To solve this problem, the goal
is to provide a decision rule for choosing, at each time step, the next action
to perform in light of known requests and probabilistic knowledge on requests
likelihood. We introduce a new decision rule, called Global Stochastic
Assessment (GSA) rule for the DS-VRPTW, and we compare it with existing
decision rules, such as MSA. In particular, we show that GSA fully integrates
nonanticipativity constraints so that it leads to better decisions in our
stochastic context. We describe a new heuristic approach for efficiently
approximating our GSA rule. We introduce a new waiting strategy. Experiments on
dynamic and stochastic benchmarks, which include instances of different degrees
of dynamism, show that not only our approach is competitive with
state-of-the-art methods, but also enables to compute meaningful offline
solutions to fully dynamic problems where absolutely no a priori customer
request is provided.Comment: Extended version of the same-name study submitted for publication in
conference CPAIOR201
Soccer Team Vectors
In this work we present STEVE - Soccer TEam VEctors, a principled approach
for learning real valued vectors for soccer teams where similar teams are close
to each other in the resulting vector space. STEVE only relies on freely
available information about the matches teams played in the past. These vectors
can serve as input to various machine learning tasks. Evaluating on the task of
team market value estimation, STEVE outperforms all its competitors. Moreover,
we use STEVE for similarity search and to rank soccer teams.Comment: 11 pages, 1 figure; This paper was presented at the 6th Workshop on
Machine Learning and Data Mining for Sports Analytics at ECML/PKDD 2019,
W\"urzburg, Germany, 201
A reduced integer programming model for the ferry scheduling problem
We present an integer programming model for the ferry scheduling problem,
improving existing models in various ways. In particular, our model has reduced
size in terms of the number of variables and constraints compared to existing
models by a factor of approximately O(n), where n being the number of ports.
The model also handles efficiently load/unload time constraints, crew
scheduling and passenger transfers. Experiments using real world data produced
high quality solutions in 12 hours using CPLEX 12.4 with a performance
guarantee of within 15% of optimality, on average. This establishes that using
a general purpose integer programming solver is a viable alternative in solving
the ferry scheduling problem of moderate size.Comment: To appear in Public Transpor
The UEFA Champions League seeding is not strategy-proof since the 2015/16 season
Fairness has several interpretations in sports, one of them being that the
rules should guarantee incentive compatibility, namely, a team cannot be worse
off due to better results in any feasible scenario. The current seeding regime
of the most prestigious annual European club football tournament, the UEFA
(Union of European Football Associations) Champions League, is shown to violate
this requirement since the 2015/16 season. In particular, if the titleholder
qualifies for the first pot by being a champion in a high-ranked league, its
slot is given to a team from a lower-ranked association, which can harm a top
club from the domestic championship of the titleholder. However, filling all
vacancies through the national leagues excludes the presence of perverse
incentives. UEFA is encouraged to introduce this policy from the 2021-24 cycle
onwards.Comment: 11 pages, 1 figure, 1 tabl
Tank allocation problems in maritime bulk shipping
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In real world maritime routing problems, many restrictions and regulations influence the daily operations. The effects of several of these restrictions have not yet been studied in depth from an operations research perspective. This paper introduces the problem of allocating bulk cargoes to tanks in maritime shipping. A model and several variations are presented, and it is shown that the main problem consists of a number of complicating constraints. The problem studied is crucial when determining whether a given route is feasible for a given ship, and computational experiments are performed to assess the difficulty of solving realistically sized instances. The proposed formulation is hoped to provide a suitable starting point for research on stowage problems in maritime bulk shipping. (C) 2009 Elsevier Ltd. All rights reserved.361130513060Research Council of NorwayConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
2D-Packing with an Application to Stowage in Roll-On Roll-Off Liner Shipping
Roll-on/Roll-off (RoRo) ships represent the primary source for transporting vehicles and other types of rolling material over long distances. In this paper we focus on operational decisions related to stowage of cargoes for a RoRo ship voyage visiting a given set of loading and unloading ports. By focusing on stowage on one deck on board the ship, this can be viewed as a special version of a 2-dimensional packing problem with a number of additional considerations, such as one wants to place vehicles that belong to the same shipment close to each other to ease the loading and unloading. Another important aspect of this problem is shifting, which means temporarily moving some vehicles to make an entry/exit route for the vehicles that are to be loaded/unloaded at the given port. We present several versions of a new mixed integer programming (MIP) formulation for the problem. Computational results show that the model provides good solutions on small sized problem instances.acceptedVersio