LotRelax

Project funded by the 2011 ANR research funding program for young researchers

Participants
- Dr Céline Gicquel (coordinator)
- Pr Michel Minoux
- Pr Abdel Lisser

Fierce competition in today's global market forces industrial companies to better design and manage their supply chains. In particular, making the right decisions regarding one of the core supply chain processes, goods production, directly affects the productivity and hence the competitiveness of a company.

Industrial production management involves, among others, deciding about which products should be made, when and in which quantity. Despite its rather simple definition, production planning is most often a difficult task for industrial managers who can be overwhelmed by the complexity of the problem. This is particularly the case when production planning involves lot-sizing and scheduling decisions. This arises whenever start-up operations such as tool changes are required between production runs of different products on a machine. In this situation, finding the right quantity to produce after a start-up, i.e. the lot size, requires reaching a good trade-off between start-up costs and inventory holding costs. 

Lot-sizing and scheduling leads to the formulation of difficult combinatorial optimization problems. A wide variety of solution techniques from the Operations Research field have been proposed to solve them. The scientific challenge here is to develop optimization methods in which the production system is modelled with the required accuracy and which are capable of providing guaranteed optimal or near-optimal production plans within reasonable computation times.                              

The objective of project LotRelax is to contribute in solving this scientific challenge, in particular by exploiting one of the latest advances in applied mathematics : semi-definite programming.

Journal papers

C. Gicquel, M. Minoux. Multi-product valid inequalities for the discrete lot-sizing and scheduling problem. Computers & Operations Research, 2015, vol. 54, pp 12-20.

C. Gicquel,  M. Minoux, A. Lisser. An evaluation of semidefinite programming based approaches for discrete lot-sizing problems. European Journal of Operational Research, 2014, vol. 137(2), pp 498–507.

International conferences with proceedings

C. Gicquel and J. Cheng. Solving a stochastic lot-sizing problem with a modified sample approximation approach. 44^th International Conference on Computers and Industrial Engineering. October 2014, Istanbul, Turquie.

C. Gicquel and M. Minoux. New multi-product valid inequalities for a discrete lot-sizing problem. 3^rd International Conference on Operations Research and Entreprise Systems. March 2014, Angers, France. (8 pages). Best Application Paper Award.

C. Gicquel and M. Minoux. A tight MILP formulation based on multi-product valid inequalities for a lot-sizing problem. International Conference on Industrial Engineering and Systems Management. Octobre 2013, Rabat, Maroc (8 pages).

C. Gicquel, A. Lisser and M. Minoux. Tight lower bounds by semidefinite relaxations for the discrete lot-sizing and scheduling problem with sequence-dependent changeover costs. 9^th International Conference of Modeling, Optimization and Simulation. Juin 2012, Bordeaux,  France (9 pages).

J. Cheng, C. Gicquel and A. Lisser. A second-order cone programming approximation to joint chance-constrained linear programs. Internationl Symposium of Combinatorial Optimisation. Avril 2012, Athènes, Grêce. Published in Lecture Notes in Computer Science, 2012, vol. 7422, 71-80.

Other international conferences

C. Gicquel, J. Cheng and A. Lisser. A joint chance-constraint programming approach for a stochastic lot-sizing problem. International Workshop on Lot Sizing. August 2014, Porto, Portugal.

 J. Cheng, A. Lisser and C. Gicquel. A modified sample spproximation method for chance constrained problems. SIAM Conference on optimization. May 2014, San Diego, USA.

C. Gicquel and M. Minoux. Multi-product valid inequalities for the DLSP with sequence-dependent changeover costs. International Workshop on Lot Sizing. August 2013, Bruxelles, Belgium.

C. Gicquel, A. Lisser and M. Minoux. Semidefinite relaxation for the DLSP with sequence-dependent changeover costs. International Workshop on Lot Sizing. August  2012, Rotterdam, Netherlands.

C. Gicquel, A. Lisser and M. Minoux. Semidefinite relaxation of a lot-sizing problem with sequence-dependent changeover costs. International Symposium of Combinatorial Optimisation. April 2012, Athen, Greece.