4 Presentations

• 
  10:30 AM - 10:55 AM

  A location problem for cash management centers

  • Abdullah Dasci, presenter, Sabanci University
  • Burcu Keskin, University of Alabama
  • Rongbing Huang, York University

  Banks manage cash logistics operations, such as satisfying cash needs of branches and ATMs or collecting extra cash and other valuables, through cash management centers (CMCs) located across the geography. In this talk, we present a mathematical program to optimally locate CMCs in a geographical market and discuss solution approaches.

• 
  10:55 AM - 11:20 AM

  Branch-and-benders-cut algorithms for the single source capacitated facility location problem

  • Furkan Enderer, presenter, Université Concordia
  • Bernard Gendron, Université de Montréal, CIRRELT
  • Claudio Contardo, GERAD - ESG UQÀM

  We present two Benders decomposition schemes and a Benders-Branch-and-Cut based exact algorithm for the Single Source Capacitated Facility Location Problem (SSCFLP). In our implementation the Benders subproblems are formulated as set partitioning problems from which LP-based Benders cuts and canonical cuts are derived. Numerical results on benchmark instances demonstrate the effectiveness of the proposed algorithm in reasonable computation times.

• 
  11:20 AM - 11:45 AM

  Formulations and approximation algorithms for multi-level facility location problems

  • Camilo Ortiz, presenter, Concordia University
  • Ivan Contreras, Concordia University
  • Gilbert Laporte, HEC Montréal

  We study multi-level uncapacitated p-location problems, a general class of facility location problems. We use a combinatorial representation of the general problem where the objective function satisfies the submodularity property, and we exploit this characterization to derive worst-case bounds for a greedy heuristic. We obtain sharper bounds when the setup cost for opening facilities is zero. Moreover, we introduce a mixed integer linear programming formulation for the problem based on the submodularity property. Some computational results are summarized in the presentation.

• 
  11:45 AM - 12:10 PM

  Facility location under service level constraints for heterogeneous customers

  • Sachin Jayaswal, Indian Institute of Management Ahmedabad
  • Navneet Vidyarthi, presenter, Concordia University

  We study the problem of locating service facilities to serve heterogeneous customers. Customers
  requiring service are classified as either high priority or low priority, where high priority patients are always
  served on a priority basis. The problem is to optimally locate service facilities and allocate their service
  zones to satisfy the coverage and service level constraints defined based on waiting time distribution of each priority class. For this, we model the network of service facilities as spatially distributed priority queues, whose locations and user allocations need to be determined. The resulting integer programming problem is challenging to solve, especially in absence of any known analytical expression for the service level function of low priority customers. We develop a cutting plane based solution algorithm, exploiting the service level function of low priority customers to approximate
  its non-linearity using tangent planes, determined numerically using matrix geometric method.