Le laboratoire Samovar accueille M. Alexandre Brandwajn ( Computer Engineering, UCSC, USA) pour une présentation intitulée « Multi-server preemptive priority queue with general arrivals and service times »

Quand: Le Jeudi 26 septembre 2019, à 10h30
Où: En salle A03, à Télécom SudParis, Evry

Titre: Multi-server preemptive priority queue with general arrivals and service times
Alexandre Brandwajn, Computer Engineering, UCSC, USA
(joint work with Thomas Begin, ENS-Lyon, France)

Abstract :
We present a simple approximate solution for preemptive-resume queues with multiple servers, general service and inter-arrival time distributions. In our solution, we solve priority levels one at a time in the order of decreasing priorities. We solve each priority level approximately using a reduced state description. The complexity of our approximate solution in terms of the number of equations solved grows linearly with the number of servers and priority levels.
Numerical results from a large number of examples indicate that, overall, in the case of Poisson and quasi-Poisson arrivals, expected relative error for the mean number of customers in the system tends to be below 2% while the corresponding median relative error stays below 0.25%. The good accuracy of our approximation appears to extend to the case of general times between arrivals, with expected relative errors for the mean number in system below 5% even for a Pareto-like distribution of inter-arrival times with a large coefficient of variation. Thus, the proposed approximation provides a relatively simple and generally accurate approach to preemptive-resume queues with larger numbers of servers and general distributions of service and inter-arrival times.

Brief biography
Alexandre Brandwajn holds a Ingénieur Civil des Télécommunications degree from the Ecole Nationale Supéreure des Télécommunications in Pairs, and a Docteur d’Etat in Computer Science degree from the University of Paris VI. He worked as researcher at the Institut de Recherche en Informatique et Automatique (IRIA), France; then, he was on the faculty of the Ecole Nationale Superieure des Telecommunications in Paris where he directed a project in adaptive computer architecture. Later he joined Amdahl Corporation in Sunnyvale, California, where he was a senior computer architect, and then manager of Systems Analysis group. Since 1985, he is a professor of Computer Engineering at the University of California at Santa Cruz and President of PALLAS International Corporation in the SF Bay Area. His current research interests include efficient solution of systems with large state space, application of conditional probability in the solution of performance models, models of virtualized systems, and efficient solution of priority systems.