Effective use of constraint A set of activities as same starting time

[Daniel]

Hey All,

In our high school timetable we have 2 types of lessons length in a day, 40 min lessons and 1 hour lessons. To address that we setup our lessons as 20 min lessons and made:
Single lesson = duration 2
1 hour lesson = duration 3
Double lesson = duration 4

Our day looks like this:
20 min x 6
break
20 min x 7
break
20 min x 3
day ends

We don't allow 1 hour lessons or double lessons to span across a break and FET takes care of that just fine as is.
ATM i m testing each form on it's own with minimal constrains, to make sure our lessons structure is valid, Over all FET is able to generate the form time table but it is slow we have ~250 activities in a form and with no constraints (just basic comp) it can take up to 10 min to get the time table for a single form.

With our primary school that got about 600 activities in all forms with no constraints but the basics the timetable is ready in a few seconds.


I think there are 2 mine reasons for this:
1. If FET slots a 1 hour lesson in the first part of the day it must be followed by a 1 hour lesson or else there will be a free 20 min slot and we don't have 20 min lessons or free space and it makes the solver work harder for no good reason. I could not fined and constraint to use for this case.

2. Options blocks where students are split to groups can have a structure of 4,3,2 lessons, and FET can slot options with duration 3 and 4 at same time resulting again in unnecessary searching. for this I was thinking I could add a activities have same starting time constraint . for activities with the same duration for a block, will this result in a speed up in your opinion ? I can give it a try but it is a lot of work to add all the constraints

I attached a file with a single form.

thanks,

Daniel

[Liviu Lalescu]

Unnecessary search is not a problem for FET, I think and I hope. But same starting time constraints may help, if they are needed.

I did a test, with your previous file (TIMETABLE.fet), it is not solved after 14 minutes. The current file (high school.fet) is solved in about 1-2 minutes. The advice would be to add all the students in the current file and see how it goes.

Please let me know.