Page 186 - ExtendSim User Guide
P. 186

160 Routing
Items from several sources
Input Line Balancing model
The Input Line Balancing model is the same as the Merging Inputs model, except a Max & Min block looks at the length for each of the queues and sends that information to the Select Item In block.
Input Line Balancing model
On the Max & Min block, the con output connector tells which of the inputs has the largest value, in this case it indicates the longest queue. This tells the Select Item In block which queue to retrieve the next item from. In the dialog of the Select Item In block, Select input based on: select connector and Top input is chosen by Select value: 1 have been selected. As you can see from the cloned Throughput table, items are drawn in a balanced man- ner from each line, and the queue lengths are almost equal, as opposed to what happened in the Merging Inputs model, earlier.
Throw Item and Catch Item blocks for merging item streams
The previous examples discussed routing items using connections to blocks that are nearby and at the same level of hierarchy. Sometimes, especially in large models, it is necessary to send an item to a different hierarchical layer. The Throw Item and Catch Item blocks are especially useful when there are items from various locations in a model (even from various hierarchical levels) that need to be sent to one place. Note that these blocks are used as an adjunct to rout- ing, not a replacement for the methods described previously.
Throw Item and Catch Item blocks pass items without connections and can even be used deep within nested hierarchical blocks to send items to other hierarchical blocks. For that reason, they are sometimes used instead of the Select Item In and Select Item Out blocks.
☞ Throw and Catch blocks should only be used when named connections will not be sufficient. For instance, to pass items through different levels of hierarchy or to use the routing features on the Throw and Catch blocks.
Throw & Catch model
The Throw Item and Catch Item blocks can also be used to merge several item flows into one stream. In the following example, three Throw Item blocks route items to Shipping, which is a
Discrete Event

   184   185   186   187   188