org.javades.jqueues.r5.entity.jq.queue.nonpreemptive

Class AbstractNonPreemptiveWorkConservingSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

java.lang.Object

org.javades.jqueues.r5.entity.AbstractSimEntity

org.javades.jqueues.r5.entity.jq.AbstractSimJQ<J,Q>

org.javades.jqueues.r5.entity.jq.queue.AbstractSimQueue<J,Q>

org.javades.jqueues.r5.entity.jq.queue.AbstractClassicSimQueue<J,Q>

org.javades.jqueues.r5.entity.jq.queue.nonpreemptive.AbstractNonPreemptiveWorkConservingSimQueue<J,Q>

Type Parameters:

J - The type of SimJobs supported.

Q - The type of SimQueues supported.

All Implemented Interfaces:

SimQueue<J,Q>, SimQoS<J,Q>, SimEntity, org.javades.jsimulation.r5.SimEventListResetListener

Direct Known Subclasses:

FCFS, FCFS_B, FCFS_B_c, FCFS_c, IC, IS, IS_CST, LCFS, LCFS_B, LJF, NoBuffer_c, RANDOM, SJF

public abstract class AbstractNonPreemptiveWorkConservingSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>
extends AbstractClassicSimQueue<J,Q>
implements SimQueue<J,Q>

An abstract base class for non-preemptive work-conserving queueing disciplines.

The work model for this class is that of a waiting area of possibly limited size and a service area that consists of a fixed (but possibly infinite) number of servers of equal capacity and "inter-changeable" to visiting jobs (i.e., jobs do not care by which server they are served). Arriving jobs that need to wait but find the waiting area full are dropped by default; however, sub-classes may override this and select another job from the waiting area to be dropped. Each server can only serve at most one job at a time. Once taken into service on one of the servers, jobs are served by that server until completion (unless they are revoked from service), after which they depart from the system.

In addition, implementations of this class are always work-conserving, which in this context is interpreted as follows:

• No work for the queueing system can be created or destroyed other than by the arrival of jobs, and the service provided by the server(s) to jobs.
• The queueing system always attempts to deploy its maximum service capacity to its jobs; it never lets jobs wait unnecessarily.

Note that the potential lack of server-access credits inhibits any implementation of SimQueue to be truly work-conserving. The requirement of work-conservation should therefore be annotated with "given sufficient server-access credits".

Implementations allow (through inheritance) the job requested service time to be (positive) infinite. Jobs with that feature will never depart (through internal scheduling), even if time itself is positive or negative infinity. If time is infinite, jobs with finite service time requirement will always start and depart immediately upon arrival.

Despite the constraints and conditions outlined above, many classical non-preemptive queueing systems like FCFS, FCFS_B_c, SJF and IS are in fact work-conserving.

Implementations only need worry about:

• Resetting the queueing system, if queue-specific data structures are maintained for visiting jobs, by augmenting resetEntitySubClass().
• Inserting a job in the waiting area (possibly imposing a queue-specific structure) by overriding insertJobInQueueUponArrival(J, double).
• If needed, override selectJobToDropAtFullQueue(J, double) in order to impose a non-default drop policy.
• Selecting which job to start by implementing selectJobToStart() (the moments to start jobs are entirely managed by this class).
• If needed, override AbstractSimQueue.getServiceTimeForJob(J).
• Removing a job from the system, if queue-specific data structures are maintained for visiting jobs, by overriding removeJobFromQueueUponExit(J, double).
• If applicable, exposing the queue's QoS structure (which can only affect the waiting-area behavior) by overriding SimQoS.getQoS() and SimQoS.getQoSClass() and advertising the appropriate SimQueueQoS generic-type structure.

Author:

Jan de Jongh, TNO

Copyright (C) 2005-2017 Jan de Jongh, TNO

This file is covered by the LICENSE file in the root of this project.

Nested Class Summary

Nested classes/interfaces inherited from class org.javades.jqueues.r5.entity.AbstractSimEntity

AbstractSimEntity.Notifier, AbstractSimEntity.PreNotificationHook

Nested classes/interfaces inherited from interface org.javades.jqueues.r5.entity.jq.queue.SimQueue

SimQueue.AutoRevocationPolicy

Nested classes/interfaces inherited from interface org.javades.jqueues.r5.entity.SimEntity

SimEntity.Action, SimEntity.UnknownNotificationTypePolicy, SimEntity.UnknownOperationPolicy

Field Summary

Fields inherited from class org.javades.jqueues.r5.entity.jq.queue.AbstractSimQueue

eventsScheduled, SANITY

Fields inherited from class org.javades.jqueues.r5.entity.AbstractSimEntity

USE_ARRAY_OPTIMIZATION

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractNonPreemptiveWorkConservingSimQueue(org.javades.jsimulation.r5.SimEventList eventList, int bufferSize, int numberOfServers) Creates a non-preemptive work-conserving queue given an event list, buffer size and number of servers.

Method Summary

Modifier and Type	Method and Description
boolean	hasServerAvailable() Returns true if there are strictly fewer jobs in the service area than servers present in the system, or if the number of servers is infinite.
protected void	insertJobInQueueUponArrival(J job, double time) The default implementation does nothing.
protected void	insertJobInQueueUponStart(J job, double time) Does nothing.
boolean	isStartArmed() Returns whether a server is available.
protected void	queueAccessVacationDropSubClass(double time, J job) Calls super method (in order to make implementation final).
protected void	removeJobFromQueueUponDeparture(J departingJob, double time) Removes the job from the system and cancels its departure event (if present).
protected void	removeJobFromQueueUponDrop(J job, double time) Invokes removeJobFromQueueUponDeparture(J, double).
protected void	removeJobFromQueueUponExit(J exitingJob, double time) Removes a job that ends its visit (in whatever way) from the internal administration.
protected void	removeJobFromQueueUponRevokation(J job, double time, boolean auto) Invokes removeJobFromQueueUponDeparture(J, double).
protected void	reschedule(double time) Central rescheduling method.
protected void	rescheduleAfterArrival(J job, double time) Drops a job from the waiting area if it has overflown; otherwise reschedules.
protected void	rescheduleAfterDeparture(J departedJob, double time) Invokes reschedule(double) passing the time argument.
protected void	rescheduleAfterDrop(J job, double time) Invokes reschedule(double) passing the time argument.
protected void	rescheduleAfterRevokation(J job, double time, boolean auto) Invokes reschedule(double) passing the time argument.
protected void	rescheduleAfterStart(J job, double time) Depending on the job's requested service time, makes it depart immediately, schedules a suitable departure event, or does nothing if the job requires infinite service time.
protected void	rescheduleForNewServerAccessCredits(double time) Invokes reschedule(double) passing the time argument.
protected void	resetEntitySubClass() Invokes super-method and revokes a pending job drop.
protected J	selectJobToDropAtFullQueue(J arrivingJob, double time) Selects the job to drop from the waiting area that in case it "overflows".
protected abstract J	selectJobToStart() Selects which job in the waiting area to start next.
protected void	setServerAccessCreditsSubClass() Calls super method (in order to make implementation final).

Methods inherited from class org.javades.jqueues.r5.entity.jq.queue.AbstractClassicSimQueue

getBufferSize, getNumberOfServers

Methods inherited from class org.javades.jqueues.r5.entity.jq.queue.AbstractSimQueue

arrive, autoRevoke, cancelDepartureEvent, cancelDepartureEvent, depart, departureFromEventList, drop, getAutoRevocationPolicy, getDepartureEvents, getDepartureEvents, getFirstJob, getFirstJobInServiceArea, getFirstJobInWaitingArea, getJobs, getJobsInServiceArea, getJobsInWaitingArea, getNumberOfJobs, getNumberOfJobsInServiceArea, getNumberOfJobsInWaitingArea, getServerAccessCredits, getServiceTimeForJob, hasJobs, hasJobsInServiceArea, hasJobsInWaitingArea, hasServerAcccessCredits, isJob, isJobInServiceArea, isJobInWaitingArea, isQueueAccessVacation, registerStdOutSimQueueListener, revoke, revoke, scheduleDepartureEvent, scheduleJobArrival, setAutoRevocationPolicy, setQueueAccessVacation, setServerAccessCredits, start, takeServerAccessCredit, toStringDefault, triggerPotentialNewStartArmed, unregisterStdOutSimQueueListener

Methods inherited from class org.javades.jqueues.r5.entity.AbstractSimEntity

addPendingNotification, addPendingNotification, clearAndUnlockPendingNotificationsIfLocked, delegateOperation, doAfterNotifications, doOperation, fireAndLockPendingNotifications, getEventList, getLastUpdateTime, getRegisteredDelegatedOperations, getRegisteredNotificationTypes, getRegisteredOperations, getSimEntityListeners, getUnknownNotificationTypePolicy, getUnknownOperationPolicy, isIgnoreEventListReset, notifyEventListReset, registerDelegatedOperation, registerNotificationType, registerOperation, registerPreEventHook, registerPreNotificationHook, registerPreUpdateHook, registerSimEntityListener, registerStdOutSimEntityListener, removeDelegationForOperation, resetEntity, setIgnoreEventListReset, setName, setUnknownNotificationTypePolicy, setUnknownOperationPolicy, toString, unregisterSimEntityListener, unregisterStdOutSimEntityListener, update

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.javades.jqueues.r5.entity.jq.queue.SimQueue

arrive, getAutoRevocationPolicy, getCopySimQueue, getJobs, getJobsInServiceArea, getJobsInWaitingArea, getNumberOfJobs, getNumberOfJobsInServiceArea, getNumberOfJobsInWaitingArea, getServerAccessCredits, isJob, isJobInServiceArea, isJobInWaitingArea, isQueueAccessVacation, revoke, revoke, setAutoRevocationPolicy, setQueueAccessVacation, setServerAccessCredits

Methods inherited from interface org.javades.jqueues.r5.entity.SimEntity

doAfterNotifications, doOperation, getEventList, getLastUpdateTime, getRegisteredNotificationTypes, getRegisteredOperations, getSimEntityListeners, getUnknownNotificationTypePolicy, getUnknownOperationPolicy, isIgnoreEventListReset, registerSimEntityListener, resetEntity, setIgnoreEventListReset, setName, setUnknownNotificationTypePolicy, setUnknownOperationPolicy, toStringDefault, unregisterSimEntityListener, update

Methods inherited from interface org.javades.jsimulation.r5.SimEventListResetListener

notifyEventListReset

Methods inherited from interface org.javades.jqueues.r5.entity.jq.SimQoS

getQoS, getQoSClass

Constructor Detail

AbstractNonPreemptiveWorkConservingSimQueue

protected AbstractNonPreemptiveWorkConservingSimQueue(org.javades.jsimulation.r5.SimEventList eventList,
                                                      int bufferSize,
                                                      int numberOfServers)

Creates a non-preemptive work-conserving queue given an event list, buffer size and number of servers.

Parameters:

eventList - The event list to use.

bufferSize - The buffer size (non-negative), Integer.MAX_VALUE is interpreted as infinity.

numberOfServers - The number of servers (non-negative), Integer.MAX_VALUE is interpreted as infinity.

Method Detail

resetEntitySubClass

protected void resetEntitySubClass()

Invokes super-method and revokes a pending job drop.

Overrides:

resetEntitySubClass in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

See Also:

insertJobInQueueUponArrival(J, double)

hasServerAvailable

public final boolean hasServerAvailable()

Returns true if there are strictly fewer jobs in the service area than servers present in the system, or if the number of servers is infinite.

Returns:

True if there are strictly fewer jobs in the service area than servers present in the system, or if the number of servers is infinite.

See Also:

AbstractClassicSimQueue.getNumberOfServers(), AbstractSimQueue.getNumberOfJobsInServiceArea()

insertJobInQueueUponArrival

protected void insertJobInQueueUponArrival(J job,
                                           double time)

The default implementation does nothing.

Specified by:

insertJobInQueueUponArrival in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that arrived.

time - The current time (i.e., arrival time of the job).

See Also:

AbstractSimQueue.arrive(double, J), AbstractSimQueue.rescheduleAfterArrival(J, double)

selectJobToDropAtFullQueue

protected J selectJobToDropAtFullQueue(J arrivingJob,
                                       double time)

Selects the job to drop from the waiting area that in case it "overflows".

Implementations only have to select either the arriving job, or a job from the waiting area to be dropped, i.e., they should not alter the internal administration and they should not reschedule. Note that the arriving job is actually present in the waiting area, see AbstractSimQueue.arrive(double, J).

The default implementation returns the arrivingJob argument; which causes the arriving job to be dropped.

Parameters:

arrivingJob - The job that arrives, non-null.

time - The job's arrival time.

Returns:

The job to drop which must be either the arriving job, or a job currently in the waiting area.

See Also:

insertJobInQueueUponArrival(J, double)

rescheduleAfterArrival

protected final void rescheduleAfterArrival(J job,
                                            double time)

Drops a job from the waiting area if it has overflown; otherwise reschedules.

The waiting area is "overflown" if it holds more (i.c., one) jobs than the buffer size and a job cannot be taken into service immediately in view of AbstractSimQueue.hasServerAcccessCredits() and isStartArmed().

If a job is to be dropped from the waiting area, it is selected through selectJobToDropAtFullQueue(J, double).

Specified by:

rescheduleAfterArrival in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that arrived (and is already present in AbstractSimQueue.getJobs()).

time - The current time (i.e., the arrival time of the job).

See Also:

insertJobInQueueUponArrival(J, double), selectJobToDropAtFullQueue(J, double), AbstractSimQueue.drop(J, double), reschedule(double)

queueAccessVacationDropSubClass

protected final void queueAccessVacationDropSubClass(double time,
                                                     J job)

Calls super method (in order to make implementation final).

Overrides:

queueAccessVacationDropSubClass in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

time - The time the job was dropped, i.e., the current time.

job - The dropped job.

See Also:

AbstractSimQueue.arrive(double, J), AbstractSimQueue.setQueueAccessVacation(double, boolean)

removeJobFromQueueUponDrop

protected final void removeJobFromQueueUponDrop(J job,
                                                double time)

Invokes removeJobFromQueueUponDeparture(J, double).

Specified by:

removeJobFromQueueUponDrop in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that is to be dropped.

time - The current time (i.e., drop time of the job).

See Also:

AbstractSimQueue.drop(J, double), AbstractSimQueue.rescheduleAfterDrop(J, double)

rescheduleAfterDrop

protected final void rescheduleAfterDrop(J job,
                                         double time)

Invokes reschedule(double) passing the time argument.

Specified by:

rescheduleAfterDrop in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The jobs that was dropped.

time - The current time (i.e., drop time of the job).

See Also:

AbstractSimQueue.drop(J, double), AbstractSimQueue.removeJobFromQueueUponDrop(J, double)

removeJobFromQueueUponRevokation

protected final void removeJobFromQueueUponRevokation(J job,
                                                      double time,
                                                      boolean auto)

Invokes removeJobFromQueueUponDeparture(J, double).

Specified by:

removeJobFromQueueUponRevokation in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that is to be revoked.

time - The current time (i.e., revocation time of the job).

auto - Whether or not this applies to an auto-revocation.

See Also:

AbstractSimQueue.revoke(double, J, boolean), AbstractSimQueue.autoRevoke(double, J), AbstractSimQueue.rescheduleAfterRevokation(J, double, boolean), SimQueue.AutoRevocationPolicy

rescheduleAfterRevokation

protected final void rescheduleAfterRevokation(J job,
                                               double time,
                                               boolean auto)

Invokes reschedule(double) passing the time argument.

Specified by:

rescheduleAfterRevokation in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The jobs that was successfully revoked.

time - The current time (i.e., revocation time of the job).

auto - Whether or not this applies to an auto-revocation.

See Also:

AbstractSimQueue.revoke(double, J, boolean), AbstractSimQueue.autoRevoke(double, J), AbstractSimQueue.removeJobFromQueueUponRevokation(J, double, boolean), SimQueue.AutoRevocationPolicy

setServerAccessCreditsSubClass

protected final void setServerAccessCreditsSubClass()

Calls super method (in order to make implementation final).

Overrides:

setServerAccessCreditsSubClass in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

See Also:

AbstractSimQueue.getServerAccessCredits(), AbstractSimQueue.setServerAccessCredits(double, int), AbstractSimQueue.rescheduleForNewServerAccessCredits(double)

rescheduleForNewServerAccessCredits

protected final void rescheduleForNewServerAccessCredits(double time)

Invokes reschedule(double) passing the time argument.

Specified by:

rescheduleForNewServerAccessCredits in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

time - The current time (i.e., the time at which new server-access credits became available).

See Also:

AbstractSimQueue.setServerAccessCredits(double, int), AbstractSimQueue.hasServerAcccessCredits()

isStartArmed

public final boolean isStartArmed()

Returns whether a server is available.

Specified by:

isStartArmed in interface SimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Returns:

Whether a server is available, i.e., the result from hasServerAvailable().

See Also:

hasServerAvailable()

selectJobToStart

protected abstract J selectJobToStart()

Selects which job in the waiting area to start next.

Implementations can assume that the waiting area is non-empty. Moreover, they are free to chose whichever job from the waiting area to start, irrespective of the structure implied by insertJobInQueueUponArrival(J, double).

Returns:

The job in the waiting area to start next, must not be null and must be present in the waiting area.

See Also:

insertJobInQueueUponArrival(J, double), reschedule(double)

insertJobInQueueUponStart

protected final void insertJobInQueueUponStart(J job,
                                               double time)

Does nothing.

Specified by:

insertJobInQueueUponStart in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that starts.

time - The current time (i.e., start time of the job).

See Also:

AbstractSimQueue.start(double, J), AbstractSimQueue.rescheduleAfterStart(J, double)

rescheduleAfterStart

protected final void rescheduleAfterStart(J job,
                                          double time)

Depending on the job's requested service time, makes it depart immediately, schedules a suitable departure event, or does nothing if the job requires infinite service time.

Performs sanity checks on the fly (job present; job not yet started; requested service time zero or positive). The time argument must match the result from AbstractSimEntity.getLastUpdateTime() (and is thus only present for sanity checking).

If a job has infinite requested service time, it will start but never depart, even if the start is scheduled at positive or negative infinity.

With zero requested service time, a job departs immediately. This is also the case if the start is at positive or negative infinity AND the job has finite requested service time.

In all other cases, a suitable departure event is scheduled through AbstractSimQueue.scheduleDepartureEvent(double, J).

Caveat: the specification above implies that NOT all jobs in the service area will have a departure event scheduled for them!

Specified by:

rescheduleAfterStart in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

job - The job that started (and is already present in AbstractSimQueue.getJobsInServiceArea().

time - The current time (i.e., the start time of the job).

See Also:

AbstractSimQueue.getServiceTimeForJob(J), AbstractSimQueue.scheduleDepartureEvent(double, J), AbstractSimQueue.depart(double, J)

removeJobFromQueueUponDeparture

protected final void removeJobFromQueueUponDeparture(J departingJob,
                                                     double time)

Removes the job from the system and cancels its departure event (if present).

Checks the presence of the departing job through AbstractSimQueue.isJob(org.javades.jqueues.r5.entity.jq.job.SimJob) (jobs must be present), cancels pending departure events for the job (if present), and invokes removeJobFromQueueUponExit(J, double).

This method also serves as entry point for removeJobFromQueueUponDrop(J, double) and removeJobFromQueueUponRevokation(J, double, boolean).

Specified by:

removeJobFromQueueUponDeparture in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

departingJob - The job that departs.

time - The departure (current) time.

Throws:

IllegalStateException - If sanity checks fail.

See Also:

removeJobFromQueueUponExit(J, double)

rescheduleAfterDeparture

protected final void rescheduleAfterDeparture(J departedJob,
                                              double time)

Invokes reschedule(double) passing the time argument.

Specified by:

rescheduleAfterDeparture in class AbstractSimQueue<J extends SimJob,Q extends AbstractNonPreemptiveWorkConservingSimQueue>

Parameters:

departedJob - The departed job.

time - The departure (current) time.

See Also:

AbstractSimQueue.depart(double, J), AbstractSimQueue.removeJobFromQueueUponDeparture(J, double)

removeJobFromQueueUponExit

protected void removeJobFromQueueUponExit(J exitingJob,
                                          double time)

Removes a job that ends its visit (in whatever way) from the internal administration.

The default implementation does nothing.

Implementations do not have to cancel (registered) departure events; this has been done by caller already.

Parameters:

exitingJob - The jobs that ends its visit, non-null.

time - The current time, i.e., the time the job ends its visit.

See Also:

removeJobFromQueueUponDrop(J, double), removeJobFromQueueUponRevokation(J, double, boolean), removeJobFromQueueUponDeparture(J, double)

reschedule

protected final void reschedule(double time)

Central rescheduling method.

As long as there are service-access credits (AbstractSimQueue.hasServerAcccessCredits()), start-able jobs (all waiting jobs) and at least one server (hasServerAvailable()) available, a single job is selected through (the sub-class specific) selectJobToStart() and started through AbstractSimQueue.start(double, J).

Parameters:

time - The time of rescheduling.

See Also:

AbstractSimQueue.hasServerAcccessCredits(), AbstractSimQueue.hasJobsInWaitingArea(), hasServerAvailable(), AbstractSimQueue.start(double, J), selectJobToStart()