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Infinite Server

Delay any number of entities for period of time

Library

Servers

Description

This block serves any number of entities for a period of time, called the service time, and then attempts to output them through the OUT port. If the OUT port is blocked, then the block holds the entities until the port becomes unblocked. If an entity in this block is scheduled to time out, then it might depart prematurely via the optional TO port. For an example that uses the TO port of a queue block in the same way, see Use Timeouts to Limit Entity Queueing Time.

An infinite server is like an infinite set of single servers connected in parallel, followed by a path combiner; the path combiner notifies entities of an unblocked path in the sequence in which the entities completed their service time, until one entity departs.

You specify the service time, which is the duration of service, via a parameter, attribute, or signal, depending on the Service time from parameter value. The block determines the service time for an entity upon its arrival. Service times are assumed to be specified in seconds.

    Note:   If you specify the service time via an event-based signal, be sure that its updates occur before the entity arrives. For common problems and troubleshooting tips, see Unexpected Use of Old Value of Signal.

The IN port of an infinite server is always available. You can interpret an infinite server as a mechanism for delaying entities. Some discussions of this block suggest this interpretation by using the word delay instead of serve.

Ports

Entity Input Ports

LabelDescription
INPort for arriving entities, which will be served.

Signal Input Ports

LabelDescription
tService time, in seconds, for a newly arrived entity. This signal must be an event-based signal. You see this port only if you set Service time from to Signal port t.

Entity Output Ports

LabelDescription
OUTPort for departing entities that have completed their service time and have not timed out while in this block.
TOPort for entities that time out while in this block. You see this port only if you select Enable TO port for timed-out entities. This port must not be blocked when an entity attempts to depart here.

Signal Output Ports

LabelDescriptionTime of Update When Statistic Is OnOrder of Update When Entity Departs
#dNumber of entities that have departed from this block via the OUT port since the start of the simulation.After entity departure via the OUT port5
#nNumber of entities in the block.After entity arrival and after entity departure4
pe

A value of 1 indicates that the block stores at least one entity that has tried and failed to depart. Such entities are pending entities.

A value of 0 indicates that the block does not store any pending entities.

After the block stores an entity that has tried and failed to depart. In this case, the signal value is 1.

After the departure of a pending entity. In this case, the signal value depends on whether any other pending entities remain in the block.

1
#peNumber of pending entities in the block.

After the block stores an entity that has tried and failed to depart.

After the departure of a pending entity.

3
wSample mean of the waiting times in this block for all entities that have departed via any port. An entity's waiting time might exceed its service time if the OUT port is blocked when the entity completes service.After entity departure2
#toNumber of entities that have timed out from this block since the start of the simulation.After entity departure via the TO port5

Output signals having the same number in the Order of Update column in the table above are updated in an arbitrary sequence relative to each other; you should not rely on a specific sequence for your simulation results.

The initial output value, which is in effect from the start of the simulation until the first update by the block, is 0 for all signals.

Dialog Box

Infinite Server Tab

Service time from

Determines whether the service time is computed from a parameter in this dialog box, a signal input port, or an attribute of the entity being served.

Service time

The service time, in seconds, for all entities. You see this field only if you set Service time from to Dialog.

Attribute name

The name of the attribute whose value the block uses as the service time for an entity. You see this field only if you set Service time from to Attribute.

Service completion event priority

The priority of the service completion event, relative to other simultaneous events in the simulation.

Timeout Tab

Enable TO port for timed-out entities

This option becomes relevant if an entity times out while in this block. Selecting this option provides a TO entity output port through which the timed-out entity departs. If you clear this option in a model that uses timeouts, see the If entity has no destination when timeout occurs parameter of the Schedule Timeout block.

Statistics Tab

These parameters determine whether the block produces data at signal output ports or omits those ports.

Number of entities departed

Allows you to use the signal output port labeled #d.

Number of entities in block

Allows you to use the signal output port labeled #n.

Pending entity present in block

Allows you to use the signal output port labeled pe.

Number of pending entities

Allows you to use the signal output port labeled #pe.

Average wait

Allows you to use the signal output port labeled w.

Number of entities timed out

Allows you to use the signal output port labeled #to.

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