set of activites has a set of prfered time slots

Started by dimzev, November 30, 2019, 06:01:22 PM

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dimzev

In trying to create a new program, I found the following case:
With 275 activity locations, it places the 125 in less than 10 seconds and gradually drops to staying for more than a day in the 66 localized activities ...
How can this be explained?
The limitation I had added was:
"a set of activities have preferred start times"
and certainly the activities were more than empty...
Where is the problem ?
why stuck on 66 ?

Liviu Lalescu

Your timetable might be too constrained. This behavior is normal for too difficult timetables.

Vangelis Karafillidis

Liviu, I think that the major problem is the dataset itself, i.e. the way that Dimitris described his timetabling problem in terms of FET.
I suggest that Dimitris should either:
1) Express the COMPLETE problem of his school in detail, which means that each student should be handled (and added) as a group or subgroup of students for the musical instrument activities. This approach is really difficult and requires a profound knowledge of FET and tricky combinations of preudo-activities along with specific types of constraints.
OR
2) Remove all the musicians (musical instruments teachers) and create a virtual teacher for ALL musical instrument activities. This virtual teacher should be constrained with "max hours daily", "min hours daily" and "max gaps per day/week". Most likely, his problem is going to become solvable by FET. Then he could "expand" the timetable of the virtual teacher into real activities with the real teachers by using a spreadsheet application.
What do you think?
Vangelis

Liviu Lalescu


dimzev

As for Vangelis's first suggestion, I don't really have much experience in using FET,
as for the second sugestion, i think it would be wrong to use a pseudo-teacher because it would narrow down the solutions ...
I explain why:
by putting the pseudo-teacher at a specific time in a particular section I exclude him from all other sections while in fact he could work at the same time different music teachers in different sections ...
how do you see it?

Vangelis Karafillidis

Hello Dimitris!

This pseudo-teacher just REPRESENTS the hours that your groups are going to be available for attending the musical instrument activities. For example, for the group B1 of the Gymnasium of a Music School, this pseudo-teacher (let's call him INSTRUMENTS) is going to have the activities B1, split = 4, duration = 1 (each one of them), etc. The easiest way to constrain this teacher is to use "teacher not available times", but only if you are sure that your timetable is not too difficult. Otherwise, I would suggest to use "max hours daily", "min hours daily" and "max gaps per day/week". FET should then solve this timetable. You can get the information of which groups are available for the musical instrument activities easily, from the timetable of this INSTRUMENTS pseudo-teacher. Then you can "expand" the timetable of the real teachers for these musical instrument activities, by assigning students to teachers or vise versa.
I noticed that in your old file you might have constrained too much your timetable.
When we have -let's say- two different activities of a subgroup B1a (for example Sports and Informatics) which take place at the same time with two subactivities of Musical Instruments for B1b, there is no reason to use the constraint "activities same starting time" for each one of the two activities. This constrains the B1a Sports activity with the 1st Musical Instruments subactivity for B1b, while B1a Sports activity, could take place at the same time with the 2nd Musical Instruments subactivity. So, it's better to use "a set of activities occupy max time slots from a selection", select all time slots, set max slots = 2, and select the four (4) above mentioned activities/subactivities.
Also, you have several constraints "teacher interval max days per week". Are you sure for these constraints? You might be wrong! After removing just these constraints, FET solves your timetable in 3-4 minutes!

Vangelis.