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Tips and Techniques
Moving items through the simulation
This chapter provides some tips, techniques, and information you may find helpful when build- ing discrete event models. The chapter covers:
• Movingitemsthroughasimulation
• How items move: holding and pushing. viewing and pulling
• Implications of connecting to multiple item inputs
• Anitem’straveltime
• Using scaling for a large number of items
• Preprocessing
• Restrictingitemsinasystem
• Connectingtotheselectconnector
• Issues for continuous blocks in discrete event models
• Settingtime-basedparametersusingaRandomNumberorLookupTableblock • Varyingadistribution’sargumentsfortheCreateblock
• AccumulatingvaluesusingaHoldingTankblock
• Cycletiming
• Itemlibraryblocks
• The Executive
• Types of blocks: residence, passing, decision, and non-item • Common connectors on Item library blocks
• Templates for common situations
• Eventscheduling
• Messaging in discrete event models
☞ The models for this chapter are located in the folder \Examples\Discrete Event\Tips.
Moving items through the simulation
In general, item input connectors on discrete event blocks will pull an item in, do something with it, wait for the block connected to the item output connector to pull the item out, then pull in another item. For example, the Activity block will pull items from preceding blocks, process those items, and hold them to be picked up by another block.
It is important that you understand the ExtendSim discrete event behavior so you can avoid making modeling errors.
How items move through the simulation
It is important to understand how items move through specific blocks so that you can avoid two rare but possible pitfalls: losing items from the simulation and having items stop moving in the simulation.
To avoid the problems discussed below, you should probably connect Create blocks to queues so that items do not get lost and connect the History block in parallel with other blocks that will actually pull in the items.
Discrete Event

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