Different weeks and additional constraints

[mininger]

Hi,

I have to make a timetable with (at least) the following constraints:
- several weeks, that are not similar because the available time change each week for the teachers
- max days per week is equal to 2 for one group of my students

As the weeks are different, I have tried to define more than 5 days per week in the data menu (by instance 3*5=15 days to consider 3 actual weeks). It works fine, I have a timetable of 15 days.
In order to impose the 2nd constraint (max 2 days/week for one group), I have tried different stuff... but nothing works, as the actual week of 5 days does not exist, only the 15 day week is considered... and FET then impose max 2 days on this "big" 15 day week... instead of 3*2 days.
Do you have an idea to overcome this problem?
Thank You
Xavier

[Liviu Lalescu]

I see three possibilities:

1. A custom version.

2. Add 3 dummy activities with duration n_hours_per_day for each students set for each real week, with preferred time slots each in their allowed week. If you need to apply students max hours daily, this might not work.

3. Consider FET to have 5 days per week and 3 x n_hours_per_day hours per day. Then use 3 constraints students interval max days per week.

Let me know if you need more clarification on anything.

[mininger]

Thank you for your answer.
solution 1: ok :-)
solution 2: (if I have well understood) in this case it means that I have to choose with the 3 dummy activities the days I do not want the course. Then I lost a degree of freedom. Or am I missing something?
solution 3: (if I have well understood) in this case, the 2 chosen days for the group are the same for the 3 weeks, no (by instance each Monday and Thursday)? If yes, I again loose a degree of freedom.
Thank you for your clarification.
Xavier

[mininger]

For solution 1: the idea should be to add the possibility to consider several weeks (when different) and some new associated constrains, by instance:
- max/min days per week
- max/min hours of a course per week
...
but I understand that it is easier said than done
Xavier

[Liviu Lalescu]

For 2: You are missing my point. Preferred times will be the whole real week. So FET can choose 3 days from the real week.

For 3: You are missing my point: Please see how the constraint students interval max days per week works. Specify interval the first real week, max times = 2.

For max hours per real week you can use a constraint activities occupy max time slots from selection. Please see how this constraint works - it is a useful one.

[mininger]

Ok, it seems that solution 2 works fine. I'll try to understand the third :-)
Thank you.

[Liviu Lalescu]

Please see the attached file for solution 3.

[Liviu Lalescu]

About solution 3: the internal code of FET accepts only maximum 3 constraints students interval max days per week for each subgroup. So, with 3 real weeks it works just to the limit. If you want more, it can be increased (I was stupid at the time of writing that code that I thought nobody needed more than 3, and I did not simply use a list instead of 3 numbers).

[mininger]

 
Thank you, it's ok for me with 3 weeks (for this year at least)