A conservation law for single-server queues and its applications

1991 ◽  
Vol 28 (1) ◽  
pp. 198-209 ◽  
Author(s):  
Genji Yamazaki ◽  
Hirotaka Sakasegawa ◽  
J. George Shanthikumar
Keyword(s):  
Conservation Law ◽  
Extremal Property ◽  
Service Discipline ◽  
Single Server ◽  
Processor Sharing ◽  
Equilibrium Equations ◽  
Common Mean ◽  
The Mean ◽  
Mean Queue Length ◽  
Basic Equations

We establish a conservation law for G/G/1 queues with any work-conserving service discipline using the equilibrium equations, also called the basic equations. We use this conservation law to prove an extremal property of the first-come firstserved (FCFS) service discipline: among all service disciplines that are work-conserving and independent of remaining service requirements for individual customers, the FCFS service discipline minimizes [maximizes] the mean sojourn time in a G/G/1 queue with independent (but not necessarily identical) service times with a common mean and new better [worse] than used (NBUE[NWUE]) distributions. This extends recent results of Halfin and Whitt (1990), Righter et al. (1990) and Yamazaki and Sakasegawa (1987a,b). In addition we use the conservation law to obtain an approximation for the mean queue length in a GI/GI/1 queue under the processor-sharing service discipline with finite degree of multiplicity, called LiPS discipline. Several numerical examples are presented which support the practical usefulness of the proposed approximation.

A conservation law for single-server queues and its applications

1991 ◽  
Vol 28 (01) ◽  
pp. 198-209 ◽  
Author(s):  
Genji Yamazaki ◽  
Hirotaka Sakasegawa ◽  
J. George Shanthikumar
Keyword(s):  
Conservation Law ◽  
Extremal Property ◽  
Service Discipline ◽  
Single Server ◽  
Processor Sharing ◽  
Equilibrium Equations ◽  
Common Mean ◽  
The Mean ◽  
Mean Queue Length ◽  
Basic Equations

We establish a conservation law forG/G/1 queues with any work-conserving service discipline using the equilibrium equations, also called the basic equations. We use this conservation law to prove an extremal property of the first-come firstserved (FCFS) service discipline: among all service disciplines that are work-conserving and independent of remaining service requirements for individual customers, the FCFS service discipline minimizes [maximizes] the mean sojourn time in aG/G/1 queue with independent (but not necessarily identical) service times with a common mean and new better [worse] than used (NBUE[NWUE]) distributions. This extends recent results of Halfin and Whitt (1990), Righter et al. (1990) and Yamazaki and Sakasegawa (1987a,b). In addition we use the conservation law to obtain an approximation for the mean queue length in aGI/GI/1 queue under the processor-sharing service discipline with finite degree of multiplicity, called LiPS discipline. Several numerical examples are presented which support the practical usefulness of the proposed approximation.

scholarly journals Pseudo-conservation laws in cyclic-service systems

1987 ◽  
Vol 24 (4) ◽  
pp. 949-964 ◽  
Author(s):  
O. J. Boxma ◽  
W. P. Groenendijk
Keyword(s):  
Conservation Laws ◽  
Conservation Law ◽  
Waiting Times ◽  
Service Systems ◽  
Stochastic Decomposition ◽  
Single Server ◽  
Weighted Sum ◽  
Cyclic Service ◽  
The Mean

This paper considers single-server, multi-queue systems with cyclic service. Non-zero switch-over times of the server between consecutive queues are assumed. A stochastic decomposition for the amount of work in such systems is obtained. This decomposition allows a short derivation of a ‘pseudo-conservation law' for a weighted sum of the mean waiting times at the various queues. Thus several recently proved conservation laws are generalised and explained.

Use of erlangian distributions for single-server queueing systems

1969 ◽  
Vol 6 (3) ◽  
pp. 584-593 ◽  
Author(s):  
T. C. T. Kotiah ◽  
J. W. Thompson ◽  
W. A. O'N. Waugh
Keyword(s):  
Queue Length ◽  
Queueing Systems ◽  
Single Server ◽  
System A ◽  
Bulk Service ◽  
Mean And Variance ◽  
The Mean ◽  
Mean Queue Length ◽  
Mean Time ◽  
Server System

SummaryThe use of Erlangian distributions has been proposed for the approximation of more general types of distributions of interarrival and service times in single-server queueing systems. Any Erlangian approximation should have the same mean and variance as the distribution it approximates, but it is not obvious what effect the various possible approximants have on the behaviour of the system. A major difference between approximants is their degree of skewness and accordingly, numerical results for various approximants are obtained for (a) the mean time spent by a customer in a simple single-server system, and (b) the mean queue length in a system with bulk service. Skewness is shown to have little effect on these quantities.

scholarly journals A Unifying Conservation Law for Single-Server Queues

2007 ◽  
Vol 44 (04) ◽  
pp. 1078-1087 ◽  
Author(s):  
Urtzi Ayesta
Keyword(s):  
Conservation Laws ◽  
Service Time ◽  
Conservation Law ◽  
Single Server ◽  
Processor Sharing ◽  
Time Sharing ◽  
Single Class ◽  
Class Time ◽  
Single Server Queues ◽  
General Service

We develop a conservation law for a multi-class GI/GI/1 queue operating under a general work-conserving scheduling discipline. For single-class single-server queues, conservation laws have been obtained for both nonanticipating and anticipating disciplines with general service time distributions. For multi-class single-server queues, conservation laws have been obtained for (i) nonanticipating disciplines with exponential service time distributions and (ii) nonpreemptive nonanticipating disciplines with general service time distributions. The unifying conservation law we develop generalizes already existing conservation laws. In addition, it covers popular nonanticipating multi-class time-sharing disciplines such as discriminatory processor sharing (DPS) and generalized processor sharing (GPS) with general service time distributions. As an application, we show that the unifying conservation law can be used to compare the expected unconditional response time under two scheduling disciplines.

scholarly journals Pseudo-conservation laws in cyclic-service systems

1987 ◽  
Vol 24 (04) ◽  
pp. 949-964 ◽  
Author(s):  
O. J. Boxma ◽  
W. P. Groenendijk
Keyword(s):  
Conservation Laws ◽  
Conservation Law ◽  
Waiting Times ◽  
Service Systems ◽  
Stochastic Decomposition ◽  
Single Server ◽  
Weighted Sum ◽  
Cyclic Service ◽  
The Mean

This paper considers single-server, multi-queue systems with cyclic service. Non-zero switch-over times of the server between consecutive queues are assumed. A stochastic decomposition for the amount of work in such systems is obtained. This decomposition allows a short derivation of a ‘pseudo-conservation law' for a weighted sum of the mean waiting times at the various queues. Thus several recently proved conservation laws are generalised and explained.

Use of erlangian distributions for single-server queueing systems

1969 ◽  
Vol 6 (03) ◽  
pp. 584-593 ◽  
Author(s):  
T. C. T. Kotiah ◽  
J. W. Thompson ◽  
W. A. O'N. Waugh
Keyword(s):  
Queue Length ◽  
Queueing Systems ◽  
Single Server ◽  
System A ◽  
Bulk Service ◽  
Mean And Variance ◽  
The Mean ◽  
Mean Queue Length ◽  
Mean Time ◽  
Server System

Summary The use of Erlangian distributions has been proposed for the approximation of more general types of distributions of interarrival and service times in single-server queueing systems. Any Erlangian approximation should have the same mean and variance as the distribution it approximates, but it is not obvious what effect the various possible approximants have on the behaviour of the system. A major difference between approximants is their degree of skewness and accordingly, numerical results for various approximants are obtained for (a) the mean time spent by a customer in a simple single-server system, and (b) the mean queue length in a system with bulk service. Skewness is shown to have little effect on these quantities.

scholarly journals A Unifying Conservation Law for Single-Server Queues

2007 ◽  
Vol 44 (4) ◽  
pp. 1078-1087 ◽  
Author(s):  
Urtzi Ayesta
Keyword(s):  
Conservation Laws ◽  
Service Time ◽  
Conservation Law ◽  
Single Server ◽  
Processor Sharing ◽  
Time Sharing ◽  
Single Class ◽  
Class Time ◽  
Single Server Queues ◽  
General Service

We develop a conservation law for a multi-class GI/GI/1 queue operating under a general work-conserving scheduling discipline. For single-class single-server queues, conservation laws have been obtained for both nonanticipating and anticipating disciplines with general service time distributions. For multi-class single-server queues, conservation laws have been obtained for (i) nonanticipating disciplines with exponential service time distributions and (ii) nonpreemptive nonanticipating disciplines with general service time distributions. The unifying conservation law we develop generalizes already existing conservation laws. In addition, it covers popular nonanticipating multi-class time-sharing disciplines such as discriminatory processor sharing (DPS) and generalized processor sharing (GPS) with general service time distributions. As an application, we show that the unifying conservation law can be used to compare the expected unconditional response time under two scheduling disciplines.

scholarly journals The Mean-field Behavior of Processor Sharing Systems with General Job Lengths Under the SQ(d) Policy

2019 ◽  
Vol 46 (3) ◽  
pp. 54-55
Author(s):  
Thirupathaiah Vasantam ◽  
Arpan Mukhopadhyay ◽  
Ravi R. Mazumdar
Keyword(s):  
Mean Field ◽  
Processor Sharing ◽  
Field Behavior ◽  
The Mean

scholarly journals The Combined Effect of Rotation and Magnetic Field on Finite-Amplitude Thermal Convection

1973 ◽  
Vol 26 (5) ◽  
pp. 617 ◽  
Author(s):  
R Van der Borght ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Field Approximation ◽  
Finite Amplitude ◽  
Combined Effect ◽  
Mean Field Approximation ◽  
Free Boundaries ◽  
Wide Range ◽  
The Mean ◽  
Basic Equations

The combined effect of an imposed rotation and magnetic field on convective transfer in a horizontal Boussinesq layer of fluid heated from below is studied in the mean field approximation. The basic equations are derived by a variational technique and their solutions are then found over a wide range of conditions, in the case of free boundaries, by numerical and analytic techniques, in particular by asymptotic and perturbation methods. The results obtained by the different techniques are shown to be in excellent agreement. As for the linear theory, the calculations predict that the simultaneous presence' of a magnetic field and rotation may produce conflicting tendencies.

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