Technical Sessions – Monday July 11

TC-08 IFORS 2011 - Melbourne
The scheduling of orders for multiple pickers on a picking line in a real life
distribution centre (Pep Stores Ltd, South Africa) is considered. The picking
line may be modelled as a variant of a unidirectional carousel system. The size
and complexity of exact solution approaches, based on generalized TSPs, is
highlighted and the need for heuristics discussed. Several heuristic approaches
are presented and their performances compared base on real life data sets.
2 - A Column Generation Approach to Real World Two-
Dimensional Cutting Problems
Enrico Malaguti, DEIS, University of Bologna, Viale
Risorgimento, 2, 40136, Bologna, Italy, emalaguti@deis.unibo.it,
Rosa Medina Durán, Paolo Toth
We consider a real-world generalization of the 2-Dimensional Guillotine Cutting
Stock Problem arising in the wooden board cutting industry. A set of
rectangular items has to be cut from rectangular stock boards, available in multiple
formats. In addition to the classical objective of trim loss minimization,
the problem also asks for the maximization of the cutting equipment productivity,
which can be obtained by cutting several identical boards in parallel. We
present an algorithm which produces high quality cutting patterns, and compare
its performance with some commercial software tools.
3 - Routing Problems with Loading Constraints
Silvano Martello, DEIS, University of Bologna, Viale
Risorgimento 2, 40136, Bologna, Italy, smartello@deis.unibo.it,
Manuel Iori
Difficult combinatorial optimization problems arise in transportation logistics
when one is interested in optimizing both the routing of vehicles and the loading
of goods into them. As the separate routing and loading problems are
already NP-hard, and very difficult to solve in practice, a fortiori their combination
is extremely challenging and stimulating. We review vehicle routing
problems with two- and three-dimensional loading constraints, as well as other
combinations of routing and special loading constraints arising from industrial
applications.
� TC-08
Tuesday, 15:00-16:30
Meeting Room 107
Bandit Processes and Resource Allocation
Stream: Dynamic Programming
Invited session
Chair: Christopher Kirkbride, The Management School, Lancaster
University, Dept. of Management Science, LA1 4YX, Lancaster,
Lancashire, United Kingdom, c.kirkbride@lancaster.ac.uk
1 - Index Policies for Some Families of Stochastic Machine
Maintenance Problems
Diego Ruiz-Hernandez, Mathematics and Statistics Dept.,
CUNEF, c/ Serrano Anguita 9, 28004, Madrid, Spain,
d.ruiz@cunef.edu
In Glazebrook, K., Ruiz-Hernandez, D. and Kirkbride, C. (2006) we established
the indexability of a class of restless bandits designed to model machine
maintenance problems in which maintenance interventions have to be scheduled
to mitigate escalating costs as machines deteriorate, and to reduce the
chances of a machine breakdown. In this paper we further develop the findings
in our earlier work by offering new families of examples for which explicit
formulae for the Whittle index can be derived. A numerical investigation
demonstrates the very strong performance of Whittle’s heuristic.
2 - Shelf Space Driven Assortment Planning for Seasonal
Consumer Goods
Joern Meissner, Kuehne Logistics University, Hamburg,
Germany, joe@meiss.com, Kevin Glazebrook, Jochen Schurr
We consider the operations of a "fast-fashion" retailer. Zara and others have
developed and invested in merchandize procurement strategies that permit lead
times as short as two weeks. Our research focuses on the use of the most
valuable resource of such a retailer: shelf space. We investigate the use of
multi-armed bandits to model the assortment decisions under demand learning.
The learning aspect is captured by a Bayesian Gamma-Poisson model. We propose
a knapsack based index heuristic that results in policies that are close to
theoretically derived upper bounds.
52
3 - Monotone Policies and Indexability for Bi-directional
Restless Bandits
Christopher Kirkbride, The Management School, Lancaster
University, Dept. of Management Science, LA1 4YX, Lancaster,
Lancashire, United Kingdom, c.kirkbride@lancaster.ac.uk
We consider a development of Whittles restless bandit model in which project
activation requires a state-dependent amount of a key resource, assumed to be
available at a constant rate, where as many projects may be activated at each
decision epoch as resource availability allows. Projects are bi-directional such
that the project state tends to move in a different direction when it is activated
from that in which it moves when passive. We demonstrate the value of the
ideas for the construction of policies for dynamic resource allocation in contexts
which involve a large number of projects.
� TC-09
Tuesday, 15:00-16:30
Meeting Room 108
VRP I
Stream: Vehicle Routing
Invited session
Chair: Arne Lokketangen, OIS, Molde College, Bitveien 2, 6411,
Molde, Norway, Arne.Lokketangen@hiMolde.no
1 - The Driver Routing Problem
Johan Oppen, Molde University College, P O Box 2110, 6402,
Molde, Norway, johan.oppen@hiMolde.no
A company offers a transportation service to bring both you and your vehicle
from one location to another. Some of the transportation tasks are known in
advance, others are called in while the plan is being executed. Several different
transportation modes are used to bring drivers between tasks. The associated
planning problem can be modelled as a dynamic and stochastic Vehicle Routing
Problem with multiple transportation modes. We present a mathematical model
and discuss solution methods for a simplified, deterministic version where all
parameter values are assumed to be known in advance.
2 - Milk Collection in Western Norway Using Trucks and
Trailers
Arild Hoff, Molde University College, P.O.Box 2110, 6425,
Molde, Norway, arild.hoff@himolde.no, Arne Løkketangen
Milk collection is a problem which is well known in rural areas all around the
world. This talk considers a real world problem for a Norwegian dairy company
collecting raw milk from farmers. Most farms are inaccessible for a large
truck carrying a trailer. Thus the routes are organized as a main tour between
larger parking spots where the trailer is left behind, and the truck drives subtours
from this spots to visit the actual farms. The talk will present heuristics
for constructing such tours and computational results comparing our result with
the current plan of the company.
3 - Metaheuristics with three search spaces for the vehicle
routing problem
Christian Prins, ROSAS, University of Technology of Troyes, BP
2060 - 12 rue Marie Curie, 10010, Troyes, France,
christian.prins@utt.fr
Some effective metaheuristics for the vehicle routing problem relax vehicle capacity
and generate TSP tours, converted into VRP solutions using a splitting
procedure. The results can be improved by a systematic alternation between
the two search spaces, see the multi-start evolutionary local search of C. Prins
in "Bio-inspired algorithms for the vehicle routing problem’, Studies in Computational
Intelligence 161, 35-53, Springer, 2009. The talk presents a metaheuristic
with a third search space, defined by the partitions of customers into
clusters compatible with vehicle capacity.
4 - Multiobjective VRP Decision Support
Arne Løkketangen, Molde University College, Britveien 2, 6411,
Molde, Norway, arne.lokketangen@himolde.no, Johan Oppen,
Jorge Oyola, David Woodruff
Due to the simplifications inherit in the modeling process, a Decision Maker
(DM) often wants to see a set of good solution instead of just the optimal one.
Also, the DM might often be interested in focusing on a set of solutions fulfilling
certain conditions that are of specific importance that day, or in general, like
avoiding a certain road due to road-works. We show how the use of a measure
for the distance between solutions implemented in a Multi-Objective setting for
the VRP problem, can be used for both of these purposes.