topic Re: Queue Stuck in the Releasing State in FlexSim Forum

Queue Stuck in the Releasing State

adrian_moraZLCQV — Thu, 20 Jun 2024 22:42:27 GMT

[ FlexSim 23.0.15 ]

Hello,

It looks like Queue10a is stuck in the releasing state because at first the condition I have set in the Send to Port was false. Eventually the condition does become true, but Queue10a does not want to release the item to its designated output port. I'm guessing it's because Queue10a needs to recheck the condition for the particular item, but I'm not sure how to execute.

I have tried using ProcessFlow (EventTriggeredSource, Decide with the same condition, Move Object, Sink) and it works as intended, but the problem with this is the timing since I have other Objects with the same condition to send to port if the condition is met. When I have multiple objects checking the condition where they will send the item to designated port because for a second the condition is met. The Variable ends up with a value of -1 since two items were inputted into the system when there was only space for 1.

I guess what I'm wondering is how can I get the items in Queue10a to move by rechecking the condition for that particular item. I hope this makes sense.

Software Version = 23.0.2

Thank you,

Re: Queue Stuck in the Releasing State

Paula_LG — Fri, 21 Jun 2024 06:51:13 GMT

Hi Adrian,

Have you tried using a zone with max content one? The structure should be very similar: EventTriggeredSource, Enter Zone, Decide with the same condition, Move Object, Exit Zone, Sink. This way, you make sure that there's only one item at a time evaluating if it can enter the next object and the rest of them will enter the decide activity once this first one has already left, returning false and not exiting.

I hope it helps!

Re: Queue Stuck in the Releasing State

adrian_moraZLCQV — Mon, 24 Jun 2024 15:51:15 GMT

Hi Paula,

Yes, I have utilized the Zone feature; however, my variable still reaching -1 meaning that two items were meeting the condition and released two items at once when I only had room for one item. This is mostly due to my 3d objects having the same condition (Queues and/or Processors) and for that one second where the condition is true any object or process flow decide activity executing this condition will release its object. At times multiple items are released resulting in -1.

I'm wondering if there is a way where we can execute the condition again for the items in the queue. It looks as if the condition was initiated when it first arrived in the queue but it was false so the item stays in the queue. After that, the item stays in the queue forever because there is nothing telling the queue to check the condition again for that particular item.

Thank you,

Re: Queue Stuck in the Releasing State

adrian_moraZLCQV — Mon, 24 Jun 2024 23:28:35 GMT

For some reason, I have the same code snippet implemented in the processor (far right of the video) that decremented the Current value from 2 to 1. In the processor (far left of the video) that did not execute the code snippet which needed to decrement the Current value from 1 to 0. Instead, the next time the code snippet is executed at another object then it realizes we have -1 in the system (inputting two items when the value is at 1.) Why is the code snippet trigger on entry not working? It works every time before this, but at this particular time it decides not to work.

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Re: Queue Stuck in the Releasing State

adrian_moraZLCQV — Tue, 25 Jun 2024 00:43:53 GMT

I think I figured out what the problem was - the snippet code counts all the subnodes.length of each processor I call out that I need to maintain. However, when an operator is transporting the unit from one processor to another, the subnodes.length command does not count it when I need it to count since the item is still within the same operation and utilizing the same resource (trackedvariable).

Now, another issue occurs where all the available spaces in the tracked variable are accounted for at 0. I stop the input of the processors affected with .input.stop, but since the task sequence has been generated for this particular operator it will continue until it finishes its task and load the item on the processor (and sabotage the count and turn the count to -1) although the processor's input is stopped. Is there a way for the operator to reevaluate the situation.

Re: Queue Stuck in the Releasing State

moehlmann_fe — Tue, 25 Jun 2024 06:23:56 GMT

In theory that would be probably be possible but I am sure that there must be an easier way to handle this.

Could you explain a bit more about what you are trying to achieve in the model? It looks like you are trying to limit the amount of items present in a chain of processors. The tracked variable denotes how many processors of some type are available?

Re: Queue Stuck in the Releasing State

adrian_moraZLCQV — Tue, 25 Jun 2024 15:34:21 GMT

I'm going back to square one on this model. There is a queue with a Conditional Port as the Send to Port. When the condition is false the item stays in the queue, but at some point the condition becomes true. However; when the condition becomes true, the initial item that had a false condition does not move. Rather the new item going through the queue will be sent through the port.

How can I send to port the items in the queue when the condition eventually becomes true? Is there a way to re-execute the condition for the item stuck in the queue?

Please see attached model for an example. As you can see all the items that failed the condition and have been accumulated in the queue will stay there forever because of the send to port condition. If you remove the conditional port to first available, then it works the way I want it to but the tracked variable goes past 0 to -1 which is wrong.

Example.fsm

Re: Queue Stuck in the Releasing State

moehlmann_fe — Tue, 25 Jun 2024 16:44:06 GMT

In general, whenever you have a case like this, where you want to re-check some condition, try to wait for the condition in the first place.

Here that means setting the queue to not release items by itself at all. Then react to each item entering with an Event-Triggered Source in Process Flow, have the token wait for the condition to be true, then release the item.

You currently also set the TR in each object's entry trigger. It would be better to initialize it once at the start of the model. Then only increment/decrement it when applicable (when an item is released or exits the chain of processors).

example_1.fsm

Re: Queue Stuck in the Releasing State

adrian_moraZLCQV — Tue, 25 Jun 2024 17:18:05 GMT

Looks good, this method should work just fine on the prime model. Thank you Felix and as always, its much appreciated!