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Finite-Source Multiserver Queue with Preemptive Priorities. Alexandre Brandwajn School of Engineering University of California, Santa Cruz alexb@cse.ucsc.edu. Plan. Motivation System considered Simple recurrent analysis Alternative method Classes on several priority levels Conclusions.
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Finite-Source Multiserver Queue with Preemptive Priorities Alexandre Brandwajn School of Engineering University of California, Santa Cruz alexb@cse.ucsc.edu
Plan • Motivation • System considered • Simple recurrent analysis • Alternative method • Classes on several priority levels • Conclusions
Motivation • Priority service • computer application • Finite number of request sources • Multiple servers • Arbitrary number of classes
Assumptions • M servers • c classes • exponentially distributed • idle times • service demands • 1 class / priority level
Assumptions • Class i, i = 1,…c • Ni sources • 1/li mean idle time • 1/mi mean service demand • Class 1 highest priority
Simple recurrent analysis • One class at a time • state description (ni,li) • ni users of class i • li servers unavailable • servers • vanish ai(ni,li) • reappear bi(ni,li)
Simple recurrent analysis • Approximation • ai(ni,li) ai(li) • bi(ni,li) bi(li) • two-dimensional birth & death • p(ni,li) • starting with class 1
Simple recurrent analysis • Generally within confidence intervals • occasionally more significant errors • more likely with longer service at higher priority • not systematic • growth with ratio of service times • peak and vanish
Alternative approach • Pair (i, i+1) • State description (ni,ni+1,li) • ni, ni+1 users of class i and i+1 • li servers unavailable to pair
Alternative approach • Servers • vanish ai(ni,li) • reappear bi(ni,li) • Pair (1,2) keep • other (i,i+1) keep results for i+1