Switch

Switch: Enabling an item to choose alternate paths

Switches enable items to dynamically select from a number of possible paths.

They are typically used in situations where items select shortest queues (ie. people queuing for ATM machines) or where an item can be processed by a number of servers.

The switch will choose from any paths along which the item can proceed (ie. flows which are not blocked). If none are available, the item will become blocked until one becomes available.

Different path selection rules are available through various switch 'Modes'.

Path selection can also be made according to attributes. This enables a switch to direct an item according to a characteristic the item carries, or according to an attribute of the model, either of which may be changed during the course of a model run.

Switches can also act like a gate, blocking the progress of items.

Due to the way Planimate® manages the progress of items, gating is a setting that is turned off or on.

Switches are classified as “Logical Only” - they cannot hold items.

Switch States

Switches are always idle.

They do not interact directly with items in the run of a model but rather influence the path that items going through the switch take.

Basic Switch Modes

Some Switch modes provide a convenient means of rule-setting that require a single setting, which Planimate® manages for you during the run.

Random Choice from Available Path

Each AVAILABLE path has an equal chance of being selected.

For full details refer to this page: Random Choice from Available Path

First Available Path

The switch selects from the AVAILABLE paths, the lowest numbered path.

For full details refer to this page: First Available Path

Shortest Queue

The switch selects from the AVAILABLE paths, the path that links to the Capacity Object (i.e. Queue, MultiServer, PickUp, Dispatcher, Splitter (and Spatial link??) that is holding the least number of items.

For full details refer to this page: Shortest Queue

Sequential

The switch will cycle between the available paths beginning with the lowest path number.

The switch will cycle between the available paths beginning with the lowest path number.

For full details refer to this page: Sequential

Advanced Switch Modes

Advanced switch modes enable you to construct sophisticated rule sets, which can determine the path for an item based on conditions within the model, or the item’s own attributes.

Attribute

The switch uses the value of an Attribute to assign a path for the item.

For full details refer to this page: Attribute Based Branching

Condition

This mode enables you to specify a test for the Switch to perform when an item looks through it.

For full details refer to this page: Single Condition Based Branching

Multiple Conditions

This mode enables you to construct a sequence of tests for the Switch to perform when an item looks through it.

Depending on the result, your Switch may choose from a range of outgoing paths, and/or block the items progress.

Multiple Conditions offers a choice of more than two outgoing paths, whereas the Single Condition option is limited to one or two outgoing path choices.

For full details refer to this page: Multiple Condition Based Branching

Track Lookahead Separator

Track Lookahead Separator mode is an advanced mode and is used in track modelling, where the modeller is building logic to manage the lookahead rules for a Planimate Tracks model.

This mode makes it easier to separate the "far lookahead" flow from the actual item movement flow.

For full details refer to this page: Track Lookahead Separator

Gating

This option sets whether the switch can block items or not.

Different icon colours indicate what Gating has been set.

Switch Cannot Block Item

• When to Use...

You can safely assume, or it is your design intent, that items will never be blocked from passing through this switch during a model run.

Switch Can Block Items

• When to Use...

You want or believe that items attempting to pass through the switch may become blocked, and forced to wait before moving on.

About Selecting a Gating Option

Switches do not have any capacity, so an item cannot become blocked at a switch. Rather it will become blocked at the object upstream that is feeding the switch.

Some switches in your model may NEVER block an item. If so, you can take advantage of this and increase your model's run speed by setting the Gating Option so that it does not need to manage blocking of items.

Read further to better understand the issues behind Gating Option Choices.

For full details refer to this page: About Gating Options

Switch Options

Switch Object Options enable the following option to be toggled on and off:

Act As Item Guide (On)

Select this option if you want your switch to acts like a Guide. Items passing through it will animate through its position.

Disable Range Errors (Off)

During a model run, if an item looks through a switch using the Attribute mode and the switch encounters a value that is greater than the number of available paths, Planimate® considers this to be a run-time error. It displays an error message indicating that the number is out of range, and then stops the run. If you select this option, then when this switch detects an out-of-range value, it will block the item's progress. If the switch is referencing a portal attribute, the item may be allowed to proceed if that attribute later comes within range. In the case of an Item Attribute reference, the item would continue to be block the path for the duration of the model run.

Show Icon During Run (Off)

Select this option if you wish to see the switch's icon during a model run.

Switch Cannot Block Items (INI file determines default)

This Gating Option is available directly from the Switch Object Menu. If enabled, it informs the switch that the modeller does not expect items to block behind it. This speeds up the model. If an item is forcibly blocked at the switch, it causes a model stop error.

For full details refer to this page: Switch Options

Switch Object Default Settings

You can use the Planimate INI file to assign as defaults the settings you prefer for switches you select from the Object Palette. The settings you can configure are:

[Edit] AssumeNoBlocking

IF 0 (default) then:

• new switches are blocking switches
• new routines invoke lookahead

If set to 1 then:

• new switches are assume no blocking
• new routines invoke only during move

This makes it easier for new users of PL to work with blocking switches and routines.

[Edit] SwitchVisibleInRun=1

If set to non 0, newly added switches default to being visible during the run, otherwise they default to hide during run.

Refer to Editing Object Properties for information about editing properties common to all objects.

Switch Articles

• Lookahead
• About Gating Options
• Attribute Based Branching
• Track Lookahead Separator
• Multiple Condition Based Branching
• Single Condition Based Branching
• First Available Path
• Random Choice from Available Path
• Sequential
• Shortest Queue
• Switch Options
• Unblocking, Threads and Attribute Gates
• Switch Modes Choice

Switch Object Frequently Asked Questions

• I have used the system clock in a switch to act as a gate, but it doesnt work.
• I want my switch to make decisions depending on who is going through it.
• My switch works the wrong way around, the item goes down path one when it should go down path two.