Breaks, gaps and building changes

[mannaia]

Hi,

I am a bit confused about the usage of gaps and breaks within FET. In our school, a typical day is made of 5 hours, with one FET break between the 2nd and the 3rd. I would like to raise the following two points:

1) The comment for the "Max gaps per week for all teachers" states that breaks are not counted as gaps.
On the other hand, it seems that breaks are counted as gaps by the "Min gaps for building changes for all teachers" constraint. 
So far nothing too serious, since it's reasonable to have a building change for teachers during the break....Anyway, are these "impressions" correct ?

2) I have imposed "Min gaps for building changes for all teachers" constraint equal to 1 and "Max gaps per week for all teachers" = 20 (teachers gaps don't hurt too much). Students' gaps are not allowed. Many other constraints (like "Min days between activities") are applied too.
Once the timetable successfully created, I realize that "Min gaps for building changes for all teachers" constraint is sometimes skipped: some teachers have a building change between two consecutive hours (with no break in between) which is something that is not great for us, due to the time required for a building change.
The impression I have is that FET does not give the priority to the "Min gaps for building changes for all teachers", while other constraints are handled as more important and accordingly observed.
I have tried to remove the "Max gaps per week for all teachers" constraint, but the problem still persists.

How would you tackle the question ?

Thanks a lot for any help,

Mannaia

[Volker Dirr]

0. if all students/teachers have a break, then most schools just doesn't add that break/hour in the dataset at all. (because one reason is, that it decrease the printed timetable size.)
1. Yes, because some buildings have a distance of several km (not only a few meters).
2. Hmm... FET shouldn't skip a constraint. Did you use 100% weight. Is there a report about that in the conflicts.txt? What version did you use? Maybe also sent me you dataset please.

[mannaia]

0. if all students/teachers have a break, then most schools just doesn't add that break/hour in the dataset at all. (because one reason is, that it decrease the printed timetable size.)

I put a break for students/teachers because I want teachers to be allowed to change building over the break. That should work if FET handles the break as a gap. Notice that "Min gaps for building changes for all teachers" is put equal to 1.

2. Hmm... FET shouldn't skip a constraint. Did you use 100% weight. Is there a report about that in the conflicts.txt? What version did you use? Maybe also sent me you dataset please.

Yes I use 100% weight. No report in the conflicts.txt. The version is the last one, 5.18. I certainly send you the dataset...I will be grateful if you have a look.

[Volker Dirr]

Hallo,

i checked your file. fet care only about building changes between 2 different buildings. if one room has no building and the other have a building, then fet doesn't count it.
so just add also a building to the other room.

Regards,
Volker

[mannaia]

Thanks Volker,
That was a big mistake, I wouldn't have found it without your help.
Now it works as a charm

BTW: it seems reasonable to create a break in the middle of a day, that FET handles as a gap, allowing building changes over it.

Best regards
Mannaia

[vire]

Hi mannaia and Volker,

I'm posting in this topic because I have the same issue, just 8 years later First of all, I would like to express my enormous gratitude for this amazing (and free!) piece of software, it is working great so far and I can successfully generate timetables. I started learning and using it for about a week now, as well as the StElTo software.

It seems that in the timetable generation the constraint "min gaps between building changes for all teachers" is not respected, it is set to value 1 with weight 100%.
- I have added breaks, and all teachers are unavailable during all breaks. I have added this manually for each teacher, on top of the fact that breaks make students and teachers unavailable.
- All rooms are added to a building (our school uses two buildings).
- No notification of conflicts about this not-respected constraint.

Could any of you point me in the right direction? I'm using version 5.45.1.
The main thing I'm trying to achieve is that teachers, when necessary, switch buildings only during breaks, or if it can't be helped, that they do it during a gap hour.

Thanks in advance

[Volker Dirr]

It seems that in the timetable generation the constraint "min gaps between building changes for all teachers" is not respected, it is set to value 1 with weight 100%.

Please add a (sample) file, so we can check the bug. (or send it to me if it should stay private. see www.timetabling.de)

[vire]

Thanks for the quick reply, it seems to be solved now because I'm not using home rooms anymore but instead activity tags and corresponding preferred set of rooms.

[Volker Dirr]

It should work with home rooms too. If you can reproduce the bug, please sent us a sample file, since it always feels bad if we worry about bugs. But i guess/hope you done a bug somewhere while entering the data.

[vire]

I'm sorry Volker, I can't do that anymore as I keep overwriting a single save file and I've made many changes already... If it happens again I will post my .fet file here. I guess I've learned a new reason why to number versions now...

[Liviu Lalescu]

Hello, vire,

Thank you for the appreciation!

No need to duplicate the break constraint as teacher not available.

If you added all the rooms to a single building, FET will obviously place the activities in any room, not considering building constraints.