Hi everyone,
I've got a scenario where I've got a timetable that takes quite a while to build, but I've got a new requirement where a group of students can go to any of two teachers, not a specific teacher. So for a practical lesson they can go to either Teacher A or Teacher B. Is there a solution to this in FET Timetabler? If I specify a specific teacher, it doesn't build (I've let it run for over 5 hours multiple times), but without that constraint it does build.
Any help or guidance are appreciated.
I am afraid, you have to try both variants for this activity, one with Teacher A and one with Teacher B and try to solve the respective timetables. I have encountered this problem a couple of times. Unfortunately, in order to solve this type of problems a new constraint is needed, which (as Liviu told me) is extremely difficult to be implemented. The constraint we need for this type of situations is something like: "a set of activities shares min common time slots with another set of activities" (and maybe in selected time slots). I don't know if Liviu or Volker have a different opinion and suggest another approach.
Vangelis.
Hello,
Maybe, using Vangelis' idea: Say activity A1(students St, subject S) can go to teachers T1 or T2. Then add dummy A2(T1, dummy subject) and A3(T2, dummy subject), then not overlapping A2 and A3, then activities min 2 simultaneous in selected time slots allowing empty slots, select all slots, activities=A1,A2,A3.
Or a similar approach, but add A1,A2,A3 occupy max 2 time slots from selection.
Quote from: Liviu Lalescu on December 26, 2024, 09:11:15 AMHello,
Maybe, using Vangelis' idea: Say activity A1(students St, subject S) can go to teachers T1 or T2. Then add dummy A2(T1, dummy subject) and A3(T2, dummy subject), then not overlapping A2 and A3, then activities min 2 simultaneous in selected time slots allowing empty slots, select all slots, activities=A1,A2,A3.
Or a similar approach, but add A1,A2,A3 occupy max 2 time slots from selection.
I think that Adele could try this approach. But, it seems that this timetable needs quite many hours in order to solve. I suspect it is an extremely difficult one. So, if she tries this approach, other problems might occur, such as difficulties in respecting other constraints (for example teacher max hours daily, max hours continuously), which means that she would need to relax other constraints, etc in order to avoid an impossible timetable. Maybe, if she has a multi-core CPU, she might try to run two different instances of FET, with each one running one single alternative of the REAL timetable, and try to generate multiple timetables on each one, utilizing the multiple cores. Maybe this is a safer way, to achieve a timetable which respects the needs of her school...
Vangelis.
Vangelis, I think Adele has many such alternative activities, otherwise she would have surely tried your approach.
Quote from: Liviu Lalescu on December 26, 2024, 09:53:59 AMVangelis, I think Adele has many such alternative activities, otherwise she would have surely tried your approach.
Most likely, you are right. The crucial point is that the necessity for this type of constraint
"a set of activities shares min common time slots with another set of activities" (and maybe in selected time slots) seems to appear more often than I expected...
Vangelis
Yes. I am not sure if this constraint would be possible.