Tài liệu Queueing mạng lưới và chuỗi Markov P11 pptx

Optimization

Analytic performance models are very well suited as kernels in optimiza￾tion problems. Two major categories of optimization problems are static and

dynamic optimization. In the former, performance measures are computed

separately from an analytic queueing or CTMC model and treated simply

as functions (generally complex and non-linear) of the control (decision) vari￾ables. In the latter class of problems, decision variables are integrated with the

analytic performance model and hence optimization is intimately connected

with performance evaluation. We limit our discussion to static optimization.

For a treatment of dynamic optimization in the context of computer and com￾munication systems see [PGTP96], [DrLa77], [MeDii97], [MTD94], [MeFi97],

[MeSe97], and [Meer92].

Designs of early computer and communication systems made little use of

mathematical optimization techniques. Because the systems were not so com￾plex, the number of possible design alternatives was limited and a good design

decision was often obvious. This state of affairs has changed dramatically since

modern systems are very complex and requirements for high performance and

dependability have evolved. Therefore an optimal design is not obvious any

more and the number of possible design decisions can be enormous.

A system designer is called on to produce a design of an implementable sys￾tem from a given design specification. The design specification may include

cost, performance, and dependability specifications, in addition to function￾al specifications. The performance specification states how well the specified

functions (as stated in the functional specification) should perform in terms

of throughput, response time, etc. The dependability specification states how

the system tolerates component/sub-system faults. The dependability spec￾557

Queueing Networks and Markov Chains

Gunter Bolch, Stefan Greiner, Hermann de Meer, Kishor S. Trivedi

Copyright  1998 John Wiley & Sons, Inc.

Print ISBN 0-471-19366-6 Online ISBN 0-471-20058-1