Séminaire
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Date : 23 octobre 2025 14:00 - Salle :Espace Fauriel - Salle 514
Mail sorting and processing challenges at La Poste and related optimization issuesEvgeny Gurevsky - Université de Nantes |
All over the world, traditional mail delivery operators are facing a drastic decline in postal traffic volumes. In France, La Poste has seen its mail volume drop from 18 billion in 2008 to 9 billion in 2018, with a forecast of 5 billion items processed in 2025. This has had an impact on La Poste's industrial mail platforms (IMPs), leading to the closure of several of them. To remedy this situation, La Poste intends to implement a more efficient mail processing way at the remaining IMPs in order to optimize the use of the so-called sorting machines and thus improve its distribution chain.
In this presentation, we first describe the current organization of mail processing and sorting at La Poste, which is carried out in two stages using sorting machines.
Next, we show how the first sorting stage can be improved by considering a dedicated optimization problem, which can be seen as a particular variant of the one-dimensional bin-packing problem, where the number of bins is fixed and specific precedence constraints between items are considered. In this problem, the items play the role of mail and the bins represent industrial mail containers, the objective being to distribute the total volume of mail as smoothly as possible between these containers. To do this, we first propose a simple heuristic suitable for dealing with this problem, then develop a more advanced simulated annealing meta-heuristic on this basis. Both algorithms have demonstrated promising results. However, for reasons of simplicity and speed of implementation, the simple heuristic method has been chosen for deployment everywhere in France for the moment.
In the second part of this presentation, based on the algorithms developed, we show how it is possible to minimize the total number of sorting sessions, which led us to study a specific vector bin-packing problem with the propagation effect within the vectors. In this problem, the vector items play the role of carrier routes and the bins correspond to sorting sessions. Finally, we also discuss a new variant of the classic one-dimensional bin-packing problem aimed at minimizing the number of bins used, which is not studied in this work, but which can also be taken into account in the organization of two-stage mail processing and merit consideration from academic point of view.
(Joint work with Emmanuelle Amann, Élliot Braud, Arnaud Laurent and Nasser Mebarki, all from the University of Nantes, France).
Webpage: https://pagesperso.ls2n.fr/~gurevsky-e/