Pull strategy does not work for queues?

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Matthias Wanner asked Feb 15, '17 Joerg Vogel commented Dec 21, '23

Pull strategy does not work for queues?

priority-model-revisited.fsmIn my simulation, I have two sources with different flowitems. On exit at the sources of the flowitems, the sources set a label called "priority" in the flowitem. After the flowitem is placed on the first queue the operator should take the flowitem with higher priority label. Because I used the pull strategy in the following queue. I used best "Pull Best Item" with a custom label, in this case: priority. Now when I run the simulation the operator does not always take the correct item. The longer the simulation runs, the more errors occur. But if I use a processor without a queue in front and implement the pull strategy directly in the processor, the operator works correclty. Can someone help me? I dont want the operator to wait at the processor to collect the next flowitem and I want to use queues. Thanks a lot.

Software Version:

FlexSim 17.0.2

operator pull strategy queues

priority-model-revisited.fsm (29.6 KiB)

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5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Kari Payton commented · Feb 15, 2017 at 07:19 PM

Could you attach your model @matthias.wanner?

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Matthias Wanner Kari Payton commented · Feb 15, 2017 at 07:21 PM

now it should be there

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Fer Díaz commented · Dec 21, 2023 at 11:28 AM

Hello,

pullstrategy_priority.fsm I have used your script for the pull strategy of the queue.

In this simulation, I created 4 products in 4 different queues, each with a different priority, but giving higher importance to priority 1. These products are picked up by the transporter according to their priority. It works well, except for the first item taken by the transporter from queue 1, which is taken independently of its priority.

Additional information: these products are dispatched to a combiner, where they will be packed until a certain number of items is reached, depending on the product type. I utilized queue 5 before the combiner, as the combiner doesn't have a pull strategy.

I think it is related to the initialization of the variables. I would appreciate if someone can help me.

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1703157986486.png (118.4 KiB)

pullstrategy-priority.fsm (83.8 KiB)

Joerg Vogel Fer Díaz commented · Dec 21, 2023 at 12:32 PM

@Fer Díaz, please ask a new question! This question has got an accepted answer and it may a bit outdated, because other mechanism might be more effektive in newer versions of FlexSim.

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Answer 1 · 2017-02-15T21:34:39Z

Jacob Gillespie answered Feb 15, '17 Matthias Wanner commented Feb 16, '17

The problem that you are running into is that Queue1 has a Maximum Content value of 1000. Each new item isn't being blocked but reserves its spot in the queue. You could get the functionality you are looking for by setting Maximum Content to 1 and then having Queue1 send its item to an intermediary queue that has a regular Maximum Content.

priority-model-revisited-edit.fsm

queue.png (97.1 KiB)

priority-model-revisited-edit.fsm (28.7 KiB)

· 1

5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Matthias Wanner commented · Feb 16, 2017 at 06:16 AM

@Jacob Gillespie Yes! Thats it! It works. So if the queue has a max content more than 1 the pull strategy does not work, because the flowitems are not following the pull strategy but reserve a slot in the queue. Think I got it now. Thanks for your fast help!

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Answer 2 · 2017-02-15T20:09:44Z

Kari Payton answered Feb 15, '17 Matthias Wanner commented Feb 16, '17

@Matthias Wanner

If I understand what you are trying to do (use 3 queues instead of two) change the settings on queue 1 to be like the settings on processor 8. Flow Tab -> Input ->Pull Strategy -> Pull item with Maximum Custom Value -> item.priority

· 1

5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Matthias Wanner commented · Feb 16, 2017 at 06:14 AM

This solution approach I already tried, but it didnt work. Thanks for the answer! :D

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