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Q&A Using Flexsim and building models

Old 08-10-2015
Axel Kohonen
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Default Default routing for released flowitems


I have a very basic twofold question. I tried to look for an answer for it in the threads and in the user manual, but cannot find it clearly described so I thought I would ask it here. I think I have figured the answer out, but want to verify it to make sure.

The general questions are: If I have a downstream object, e.g. a processor, and 1 or 2 queues that contain released objects, what is the default order that the objects flow down to the processor? Are the flowitems released in the order they happen to be in the queue, in the order they were released, or possibly in some other order?

The two specific questions that I would want an answer to relate to the two attached models.

Model description:
The flowitem is given a numeric label “releaseTime” on creation which contains the time before which the item should be not released to the processor. Send to port of the queue is set to not release the item. At entry to the queue the time when the item should be released is calculated and the queue sends a message to itself to arrive at that time. When the queue receives the message it releases the item.

Specific questions:
  1. The model with 1 unsorted queue seems to show that the first flowitem to exit the queue is always the one that is first in the queue (FIFO) as long as the item has been released. The order the items have been released in does not matter. Is this correct? (Sorting the queue according to releasetime obviously makes the flowitems exit in the order of the releasetime then.)
  2. The model with 2 sorted queues seems to show that the processor always first takes all released objects from the queue connected to the first input port of the processor, no matter if there is an item with an earlier releasetime in the second queue. So as long as there are released items in the queue connected to the first input port of the processor they always get picked and no items flow to the processor through the seconds input port. Is this correct?
Thank you!

Kind regards,

Attached Files
File Type: fsm 1UnsortedTimedQueue-DefaultFlowOrder.fsm (19.7 KB, 346 views)
File Type: fsm 2SortedTimedQeues-DefaultFlowOrder.fsm (23.9 KB, 337 views)
Old 08-18-2015
Axel Kohonen
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Downloads: 22
Uploads: 0

Hi all,

Sorry for initially posting this in the Tips and tricks section as it was a question. However, I got this clarified with Flexsim support. See Ben's answer below.

Hi Axel,

1) Yes, you are correct. Look at the queue in the tree, then expand with the '+' button to see the flowitems inside.

The default order that flowitems appear in the tree is oldest item on top of list, with new items added to the bottom. You can use the queue's onEntry trigger to do sorting and change this ordering any way you wish (for instance by the releaseTime label, as you suggested).

When the downstream object tells the queue that it can accept a new flowitem, the queue loops through its list of flowitems from top to bottom (default FIFO), or from bottom to top (LIFO, if checked on properties page). The first item it finds that has been released will be sent downstream.

I have modified your first model to more easily see everything that is going on. Check out the tree view of the items in the queue to see what I mean. Model attached.

2) Yes, the processor notifies the upstream objects of its availability in the order of its ports. You could use pull logic on the processor to program finer-grained control of which flowitem the processor should accept next.


Ben Wilson
FlexSim Tech Support
The Following User Says Thank You to Axel Kohonen For This Useful Post:
Jing Chen (08-18-2015)

default flow, timed queue

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