OptQuest equation

Question

question

laitriminh asked Dec 22, '23 laitriminh commented Jan 4, '24

OptQuest equation

Hello everyone,

I'm facing an issue in finding the optimal position for 2 queues and 1 processor so that the average WIP (Work in Progress) at the upper two queues is minimized. The constraint here is that these 2 queues and 1 processor shouldn't overlap.

I asked the community and fortunately received suggestions on how to set up these constraints. However, when I start running the optimizer, the resulting .csv file shows that although the objective of minimizing the WIP at the two queues is achieved (Rank 1), the coordinates do not adhere to the constraints I set, causing objects to overlap.

I've attached the Flexsim file (version 2019) and some images, and I would greatly appreciate any help from the community.

best regard,

laitriminh

Cải tiến.fsm

Software Version:

FlexSim 19.0.0

optquest optimizer design

1.png (25.4 KiB)

1.png (22.7 KiB)

cai-tien.fsm (413.2 KiB)

Answer 1 · 2024-01-03T16:15:48Z

Jordan Johnson answered Jan 3, '24 Joerg Vogel commented Jan 4, '24

Here is your full constraint equation:

   ([Q7 x] < [Q8 x] - 2) 
OR ([Q8 x] < [Q7 x] - 2) 
OR ([bon tam x] < [Q8 x] - 7.5) 
OR ([Q8 x] < [bon tam x] - 7.5) 
OR ([bon tam x] < [Q7 x] - 7.5) 
OR ([Q7 x] < [bon tam x] - 7.5)

Because you are using the OR operator, the solution counts as feasible if any of the terms in that expression are true. For example, if [Q7 x] < [Q8 x] - 2, then none of the other statements are checked, so there are no constraints on other parameters. My guess is you need to look more at using additional constraints in addition to OR.

Edit:

This answer originally recommended using AND. OptQuest doesn't support AND in constraint expressions. To achieve the same result, use more than one constraint. All constraints are AND-ed together. All constraints must be satisfied for a solution to be valid.

So in this case, you probably need three constraints.

([Q7 x] < [Q8 x] - 2 OR ([Q8 x] < [Q7 x] - 2)

([bon tam x] < [Q8 x] - 7.5) OR ([Q8 x] < [bon tam x] - 7.5)

([bon tam x] < [Q7 x] - 7.5) OR ([Q7 x] < [bon tam x] - 7.5)

· 6

laitriminh commented · Jan 03 at 04:20 PM

Got the idea! Thank you

0 ·

laitriminh commented · Jan 03 at 11:46 PM

I've modified the equation as you suggested, but when I start running the optimization, I still encounter an 'Error Constraint Equation.' I'm not sure why this is happening.

0 ·

1704325517132.png (31.0 KiB)

1704325556826.png (25.1 KiB)

Joerg Vogel laitriminh commented · Jan 04 at 08:04 AM

@laitriminh, Can you explore, which equation causes this error. Please add or remove parts of it until you can identify where this error happens.

EDIT: may I suggest that you use variable names without a space character in it. It seems odd, but there existed a period in time, when it was not allowed to use any possible sequence of characters for variable names. you can replace a space character by an underscore.

0 ·

laitriminh Joerg Vogel commented · Jan 04 at 09:45 AM

I removed the space. I tried each part individually, and the optimization engine worked fine. However, when I combined 2 or 3 parts together, I encountered an error called 'Constraint Equation Error'

([bx] < [q8x] - 7.5) OR ([q8x] < [bx] - 7.5)
(([q7x] < [q8x] - 2) OR ([q8x] < [q7x] - 2)) AND (([bx] < [q8x] - 7.5) OR ([q8x] < [bx] - 7.5))
(([q7x] < [q8x] - 2) OR ([q8x] < [q7x] - 2)) AND (([bx] < [q8x] - 7.5) OR ([q8x] < [bx] - 7.5)) AND (([bx] < [q7x] - 7.5) OR ([q7x] < [bx] - 7.5))

Section Equation 1 works fine, but when additional sections are added, there's an error in the constraint equation (Equations 2 and 3).

Cải tiến.fsm

1 ·

1704361201168.png (20.1 KiB)

cai-tien.fsm (384.3 KiB)

Show more comments

question