question

Ireneusz Kaczmar avatar image
0 Likes"
Ireneusz Kaczmar asked tannerp edited

Pull strategy and shortest processing time

The model is working in pull strategy, priority is shortest processing time for 5 items. Process time for elements is: (1+1,5+2,5+2+3)/5=20/5=4,0. AvgStaytime in queue should be 4.0, but in this mdel is 4.1s why ??? Someone has any idea ? spt.fsm

FlexSim 17.0.10
pull strategy shortest processing time
spt.fsm (19.2 KiB)
5 |100000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

1 Answer

Jeff Nordgren avatar image
1 Like"
Jeff Nordgren answered tannerp edited

@Ireneusz Kaczmar

I'm not sure where you are getting your numbers from. Here is how they should be calculated.

Enter Q		Exit Q	Time in Q
1		3	2
1.5		4	2.5
2		5.5	3.5
2.5		8	5.5
3		10	7
Total			20.5
20.5/5 = 4.1

So it appears to me that FlexSim is calculating the Avg. Staytime of flowitems in the queue correctly.

· 1
5 |100000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

Ireneusz Kaczmar avatar image Ireneusz Kaczmar commented ·

Thx for your support Jeff. In my first approach I was thinking that sum creation time and suma processing time 20/5 flowitems = 4s. In my first model processing sequence of flow items was wrong. Flow sequence was 1,2,3,4,5, but for STP should be 1,2,4,3,5 for flowitems. I rebuilt my model I compared FIFO vs. SPT now is correct. I send good model spt_ok.

Could you explain me how did you get your numbers Exit Q and Time in Q, flexsim has especialy report or something else? For new case I added new label (EDD Earliest due date). Can anyone verify if the flow is good? spt-ok.fsm

0 Likes 0 ·
spt-ok.fsm (18.4 KiB)
spt-rep.jpg (44.0 KiB)
edd.jpg (41.8 KiB)