Springer Online Journal Archives 1860-2000
Abstract When controlled stochastic systems have performances which satisfy generalisedconservation laws (GCL), an objective which is linear in the performance is optimised by aGittins index policy. We develop measures of the extent to which a system fails to satisfyGCL and derive suboptimality bounds for suitable index policies in terms of such measures.These bounds are used, inter alia, to explore the robustness in performance of cm‐typerules for a multiclass G/G/1 queueing system to departures from an assumption of exponentialservice times. We also study Gittins index policies for parallel processor versions of theclassical undiscounted and discounted multi‐armed bandit problems. In the undiscountedcase, the cost of an index policy comes within a constant of the optimal cost ‐ thisconstant being independent of the number of projects submitted for scheduling. In thediscounted case, under fairly mild conditions, Gittins index policies come within an O(1) quantity ofoptimality and are hence average reward optimal when the discount rate is small enough.
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