Reevaluation of findSlot-Queries?

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Mario Moeller asked Dec 7, '20 Mario Moeller commented Dec 17, '20

Reevaluation of findSlot-Queries?

Hello,

I came across the following situation:

I want to assign flow items to a floor storage object by finding a slot via the Process Flow 'Find Slot'-activity. The problem that occured is that when flow items are queueing to enter the full floor storage, the SQL-queries in the 'Find Slot'-Activity will not be triggered/reevaluated when the first floor storage space becomes available, but only when the second flow item is being pulled out of the storage object. Thus there is always one storage space empty which could still be occupied by a queueing flow item.

I created a little example model which isolates the situation. The set breakpoint should directly navigate you to the problem.

Thank you!

Reevaluation of findSlot Queries.fsm

Software Version:

FlexSim 20.2.3

flexsim 20.2.3 warehousing findslot

reevaluation-of-findslot-queries.fsm (46.9 KiB)

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

Answer 1 · 2020-12-16T23:31:56Z

Logan Gold answered Dec 16, '20 Mario Moeller commented Dec 17, '20

This looks like a bug. The documentation for the Find Slot activity says, "The queries will be reevaluated each time an item exits the storage system, freeing up space in a slot."

I am going to send a bug report to the Developers to look into it, but I think I have a workaround for now.

You should be able to use the Max Wait Timer on the Find Slot activity and move the tokens to a Wait for Event if a slot cannot immediately be found. Then, in the Wait for Event activity, you can listen for when an On Slot Exit trigger fires - either on the FloorStorage1 object in the example model, or on the Storage System in other models if there is more than one Storage Object that the items could be sent to.

I am attaching your model with those changes made to give you a better idea of what I mean. (reevaluation-of-findslot-queries_FS1.fsm)

One thing that I have not tested is if a lot of tokens end up in the Wait for Event, or if the OnSlotExit trigger is fired a lot, I could see it slowing down the model. If that ends up being the case for you in a bigger model, then you could mitigate it depending on other factors of that model. Possibly by using a list instead of a Wait for Event activity, but I would need to know more information about the bigger model before I could tell you for sure.

reevaluation-of-findslot-queries-fs1.fsm (48.1 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.

Mario Moeller commented · Dec 17, 2020 at 03:01 PM

Thank you for your answer and for sending a bug report to the developers.

I will implement your workaround in my bigger model and will answer in this thread again if I am facing any problems in terms of slow downs.

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