Past Events

Title: Capacity upper bounds for deletion-type channels Speaker: Dr Mahdi Cheraghchi Affiliation: Dept of Computing, Imperial College London Location: 218 Huxley Building Time: 16:00 - 17:00 Abstract. We develop a systematic approach, based on convex programming and real analysis, for obtaining upper bounds on the capacity of the binary deletion channel and, more generally, channels with i.i.d. insertions and deletions. Other than the classical deletion channel, we give a special attention to the Poisson-repeat channel introduced by Mitzenmacher and Drinea (IEEE…

Title: Arrangements of Circles and Spheres leading to Convex Hulls with Minimal Boundaries Speaker: Dr Josef Kallrath Affiliation: Advanced Business Analytics, BASF SE, Germany Location: 218 Huxley Building Time: 15:00 - 16:00 Abstract. We present and solve a new computational geometry optimization problem in 2D and 3D and provide theoretical insights. Circles (2D) and Spheres (3D) with given radii should be arranged in such a way that a) they do not overlap and b) the length of the perimeter or surface…

Title: Random projections in mathematical programming Speaker: Dr Leo Liberti Affiliation: CNRS LIX, École Polytechnique Location: 218 Huxley Building Time: 15:00 - 16:00 Abstract. In the algorithmic trade-off between generality and efficiency, sometimes the only way out is to accept approximate methods. If all else fails, we can always fall back on heuristic methods. But some form of approximation guarantee is usually preferable. In this talk we shall discuss a set of approximating reformulations to various classes of mathematical programming problems…

Title: More Virtuous Smoothing and Embracing the Ghost of Rolle Speaker: Prof Jon Lee Affiliation: Industrial and Operations Engineering, College of Engineering, University of Michigan Location: LT 308 Huxley Building Time: 14:00 - 15:00 Abstract. In the context of global optimization of mixed-integer nonlinear optimization formulations, we consider smoothing univariate concave increasing functions that have poorly behaved derivative at 0 (for example, root functions). Extending earlier work of Lee and Skipper, we give general conditions under which our smoothing is concave…

Title: Computing Pessimistic Leader-Follower Equilibria with Multiple Followers Speaker: Dr Stefano Coniglio Affiliation: Dept. of Mathematical Sciences, Southampton University Location: Room 217 Huxley Building Time: 14:00 - 15:00 Abstract. We investigate the problem of computing a Leader-Follower equilibrium in Stackelberg games where two or more followers react to the strategy chosen by the (single) leader by playing a Nash Equilibrium. We consider two natural cases, the optimistic one where the followers select a Nash Equilibrium maximizing the leader's utility and the pessimistic one…

Title: Large neighbourhood Benders' search Speaker: Dr. Stephen Maher Affiliation: Lancaster University Management School Location: Room 218 Huxley Building Time: 14:00 - 15:30 Abstract. Enhancements for the Benders' decomposition algorithm can be derived from large neighbourhood search (LNS) heuristics. While mixed-integer programming (MIP) solvers are endowed with an array of LNS heuristics, their use is typically limited in bespoke Benders' decomposition implementations. To date, only ad hoc approaches have been developed to enhance the Benders' decomposition algorithm using large neighbourhood search techniques---namely…

Title: ADMM and Random Walks on Graphs Speaker: Prof. José Bento Affiliation: Dept. of Computer Science, Boston College Location: Room 217 Huxley Building Time: 11:15am - 12:30pm Abstract. A connection between the distributed alternating direction method of multipliers (ADMM) and lifted Markov chains was recently proposed by Franca et al. 2016 for a non-strictly-convex consensus problem parametrized by a graph G. This was followed by a conjecture that ADMM is faster than gradient descent by a square root factor in its convergence…

Title: Multi-level Optimization by multi-parametric programming & its use for the solution of Mixed Integer Adjustable Robust Optimization Problems Speaker: Prof. Michel Gendreau Affiliation: Dept. of Mathematics and Industrial Engineering, Polytechnique Montréal Location: LG19a, Business School Time: 2:00pm Abstract. While Vehicle Routing Problems have now been studied extensively for more than 50 years, those in which some parameters are uncertain at the time where the routes are made have received significantly less attention, in spite of the fact that there are many…