Any thoughts on my sudden output dropoff?

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Justin Brozzo asked Aug 9, '16 Adrian Haws answered Aug 9, '16

Any thoughts on my sudden output dropoff?

Hello All, @Matthew Gillespie @Matt Long @Logan Gold @Sam Stubbs

I have isolated an area of my main model here in this extremely reduced model as I believe it is the cause of my output drop off. When I run my main model it reaches its max output around 20000 minutes and stays there until 200000 minutes where it suddenly starts to drop off.

I have attached a sample in the area that I believe is causing the drop off. In this model the drop off happens much sooner but similar to the drop in my model.... In this model outputdrop.fsm between 1000 - 1500 minutes max output is reached and then it suddenly begins to drop off. I am wondering if you would be willing to provide some insight and hopefully using my model show me what I am doing that is causing this drop off.

Explaining the model:

There is an InitalSource that creates 20 objects that enter the system. While Source25 is an initial source for the inside line releasing only 5 objects into the inside line. ( I do not want the initial sources to change)

As an object from Q1 enters Processor1 it triggers source 25 to create an object ans it starts at Processor1A... The main line (Processors1-6) continue down that path and are joined with the object from the inside line at combiner1.

Queue: RemoveObjectFromQ28 destroys an object from Q28 when and object from the main line is sent to rejects. After RemoveObjectFromQ28 it is sent to a processor of time zero to trigger source26 keeping the same number of devices available for the system.

After processor6 objects go to the sink which on entry triggers source 26 again keeping the same number of devices in the system.

Ideally I am not looking to change how the objects flow. I am simply trying to discover why the output drops off. If you would please show me a way to not have that happen in this model: outputdrop.fsm I would greatly appreciate it.

Thanks again.

Software Version:

FlexSim 16.1.1

output drop off

outputdrop.fsm (26.7 KiB)

Answer 1 · 2016-08-09T16:13:41Z

Adrian Haws answered Aug 9, '16

Hi Justin,

I noticed a couple different things as I looked at your model. As you're displaying the output for Processor6, it can only process as fast as it receives items. As time progresses in the model, it has to wait longer and longer for a new item from the combiner. The combiner, in turn, has to wait longer and longer for a new item from Q_28, etc. This is shown here:

I made one small change (which you might not necessarily want to do in your model) to see how it would affect the results. I changed Q_25 to not perform batching so that items flow through more quickly. Here's what happened:

Another thing that could be accelerating the decrease in Processor6's output is what you said here: "After Processor6 objects go to the sink which on entry triggers source 26 again keeping the same number of devices in the system." Since Source 26 ultimately feeds the line that the Combiner is waiting for, this means that as Processor6's output decreases so does it's input (from the Combiner). Hopefully I've explained this clearly and you find this helpful.

output.png (15.3 KiB)

output2.png (17.3 KiB)

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