Page 332 - ExtendSim User Guide
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306 Tips and Techniques
Moving items through the simulation
Avoid this pitfall
When one block holds an item and that item is only viewed by another block, the item does not move through the simulation and is blocked. This is never desired.
For example, both screenshots to the right show a History block that has been auto-created and is viewing items in an Activity block. In the top (error) screenshot, after the Activity block has finished processing its first item, the item will have nowhere to go since it is blocked.
Connections to multiple item input connectors
You can connect from one item output connector to as many item input connectors as you want. However, since items can only be in one place at a time, the first connector to pull in the passed item gets it and the other connectors do not.
• Ifmorethanoneinputonasingleblockisfree,theitemwillarbitrarilygotoanyavailable input. (Note that the selection is arbitrary – not random.)
• If more than one block is free to accept the item, the item will go to the block that was first connected in the model. This is shown in “Implicit routing” on page 164 and “Simple paral- lel connections” on page 180.
It is more typical that you would want to specify which input connector, or which block, would get an item. For more information, see “Items going to several paths” on page 161.
Unless it is completely unimportant in the model, you should always use the Select Item In and Select Item Out blocks to explicitly state how items should be routed. Otherwise, the order in which their connections were made will dictate the routing.
An item’s travel time
In a discrete event model items travel from block to block as dictated by the connection lines. The lines between blocks indicate the path of the movement, but they don’t provide any delay to the items.
In most cases, travel time is insignificant and can be safely ignored. Where an item’s travel time is significant to the model, you can:
• Increase the delay time of destination blocks to compensate for the travel time
• Specify a minimum wait time in a Queue block’s Options tab
• ExplicitlysetatraveltimeinaTransportorConveyItemblock,asdiscussedin“Transporta- tion and material handling” on page 200. (You can easily add a Transport block between two blocks by right-clicking the leftmost block’s output connector and selecting “Add transport block”.)
Discrete Event

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