The Variance of Production Counts over a Long Time Horizon Yoni Nazarathy* EURANDOM, TU/e Contains joint work with Ahmad Al-Hanbali, Yoav Kerner, Michel Mandjes, Gideon Weiss and Ward Whitt Workshop on Stochastic Models of Manufacturing Systems Eindhoven, June 2010 *Supported by NWO-VIDI Grant 639.072.072 of Erjen Lefeber
Problem Domain: Queueing Output Processes PLANT OUTPUT - Single Server Queues - Tandem Queues - Re-Entrant Lines Desired over long term: High Throughput Low Variability Our focus: for large T
Asymptotic Variance Rate of Outputs For Renewal Processes: Variance Curves Example: Stationary stable M/M/1, D(t) is PoissonProcess( ): Example: Stationary M/M/1/1 with . D(t) is RenewalProcess(Erlang(2, )): Asymptotic Variance Rate of Outputs For Renewal Processes:
Asymptotic Variance Rate M/M/1 Non-Stop Service Burkes Theorem
The Basic Loss-Less Stable Queueing System Q(t)
Our main focus: Overloaded and critically loaded systems
GI/G/1 Non-Stop Service
Queues in Tandem (with 1 bottleneck) Bottleneck Server Just as simple…
Re-entrant Line bottleneck In the stable case:
Overloaded case --> Infinite Supply Re-entrant Line Result:
Overloaded case --> Infinite Supply Re-entrant Line 1 6 8 1 2 3 5 6 4 8 7 9 Result:
Shocking result* coming up… * at least for me
Back to Single Server (GI/G/1/K) What happens here? Balancing Reduces Asymptotic Variance of Outputs Note: the figure assumes
BRAVO Effect (illustration for M/M/1) More than a singular theoretic phenomenon
BRAVO Effect (for M/M/1/K)
Some (partial) intuition for M/M/1/K Easy to see: 1 K K-1
Questions?