03/06/2025 - 15:00 - CORE B.-135
> 2 sessions.
Henri Dehaybe (CORE)
will give a presentation on :
New Heuristics for Phylogeny Estimation under the Balanced Minimum Evolution Criterion.
Abstract :
Recent advances in the combinatorics of the Balanced Minimum Evolution Problem (BMEP) enabled the characterization of the mathematical properties that a symmetric integer matrix of order must satisfy to encode the Path-Length Matrix (PLM) of an Unrooted Binary Tree (UBT). This result, together with the identification of fundamental facet-defining inequalities for the convex hull of BMEP solutions, has led to an integer linear programming formulation that currently serves as the reference exact solution algorithm. Here, we show how to exploit these advances to improve the approximation algorithms for the problem. We first leverage the tight linear programming relaxation of this formulation to develop an enhanced Neighbor Joining–like heuristic. Next, we embed this heuristic into a Beam Search framework to further improve the quality of the solutions. Computational experiments show that the proposed algorithms outperform existing heuristics, making their use highly desirable in practice.
Thomas De Munck (CORE)
will give a presentation on :
A rolling horizon approach to coordinating ride-hailing platforms and public transit systems.
Abstract :
The integration of ride-hailing platforms with public transit systems can bring many benefits, including improved utilization of public transit, and affordable and accessible customer services. In this work, we consider the online problem of a ride-hailing platform that dispatches drivers to customers while coordinating with public transit. Customer requests arrive dynamically over time. For each request, the platform must decide (i) whether to provide door-to-door, first-mile, or last-mile service, and (ii) which driver to dispatch to the resulting service. To address this problem, we develop a rolling horizon approach based on stochastic optimization. The approach is enhanced by a route selection procedure and a Benders decomposition. In numerical experiments, we evaluate the benefits of a coordinated system under various parameter configurations and objective functions. Our results suggest that the platform and the customers can significantly benefit from coordination.