Messages

You set that time constraint only to 3 activities (id 124, 126 and 123).
I guess you want to have something like this:
FET -> Data -> timeconstraint -> Activities -> An activitiy has a set of pref. timeslots
remove that 3 constraints.

then go to
FET -> Data -> timeconstraint -> Activities -> A set of activities has a set of pref. times
now add fot tag "Allattamento" an constraint with only 1st hour allowed.

Thanks a lot for the hint! I think I have not understood very well the differences between activity, sub-activity and maybe even activity group.

Hello fetters ^_^,

this is something which is really puzzling me. I'm trying to use this simple constraint in the subject to have the activities tagged with "Allattamento" always at the first hour. There are 5 sub-activities  (5 lessons which last 1 hour) and 5 possible work days for the teacher.
However even if I generate the timetable without conflicts, the constraint does not seem to be respected. It seems so strange to me that I think I'm probably overlooking something very simple, but until now I haven't found the problem. You know when you try to turn on the TV and you are using the wrong remote control, that's the feeling. ^_^

Hello! :-)

I have 5 hours per day and a Teacher has 3 activities (lessons) of two hours each.
This teacher can work only on Monday and Saturday and it's easy to achieve this in this great program called FET.
But now he is asking for additional constraint (the more you give them the more they ask!!!!):
he should work 4 hours on Saturday and 2 hours on Monday.
How can I achieve this without forcing the specific activities to be on Saturday or on Monday?
Thx a lot!

Generalmente riesco ad esaudire quasi tutti i desiderata dei docenti a t.i. (giorno libero o non fare 2 o 3 volte la prima ora), mentre i docenti a t.d. devono accettare l'orario come viene, ho già riempito fet di vincoli e ha bisogno di avere cattedre in cui scelga lui i giorni liberi. Non posso rifiutare i desiderata, anzi un problema è il tentativo di cumulo di essi: c'è chi vorrebbe sia giorno libero che non fare le prime ore.

Io per cercare di mantenere una certa "giustizia" ho cominciato da qualche anno a tenere uno storico dei desiderata soddisfatti/insoddisfatti per fare un po' a turno.

Hello,
I just want to thank you once again.
The idea of 100% constraints is very helpful (if understood properly).

Since I use one of the not perfectly optimized constraints involving tag I have very different times to solutions, but is okay.

At least I think that is the reason.

See the attached screenshot for example.

Thanks!

Difficult to say: That is depending on your dataset and what you want to do next.
If you don't want to add (much) more constraints, then FET can get much time.
If you need to add a lot of other constraints, then FET should be able to solve it "fast". You might skip that constraints if they are not highly needed and add others first.

Times will be different with your dataset, i just talk about my difficult dataset (If i have an easy timetable, then you can replace the "half an hour" to max 5 minutes):
If i work with my dataset, then I "know" that it is ok if FET was able to place around 90% after a half hour. In that cases FET was always able to solve it (sometimes just it need just a few minutes more and sometime a few hours.)
If i work with my dataset and FET placed less then around 50% after half an hour, then there was always a bug in my dataset. So there where impossible constraints/data, but FET tried to "solve" even it is impossible. I "just check" my dataset set then. In many cases it is easy for a human to see that bug if you know where to search. Then I fix it and let FET generate again.
(If there are values between 50% and 90% after half an hour, then i just wait some more time and decide a bit later again.)
These percentages are only "correct" for my dataset (around 600 activities.)
If you have less activities, then you might need to increase the 50% and 90% limit.
If you have more activities, then i think these percentages are also ok.

I have about 160 activities and FET places about 140 almost at the start, it then usually increases that number slowly until it solves. But if there is a bug I don't think I spot any special abnormal behaviour in FET

Maybe think about this:

I prefer to split an activity into max (number of days per week) and use 100% weight.
So activity 1 is fine.
I prefer to split activity 2 as 2+2+2+2+1
So in worst case there are 4 hours per day.

Now try if the timetable is still solvable.

If it is still solveable use constraint "same day" for the first subactivity of activity 1 (duration 2) and the last subactivity of activity 2 (duration 2).
So there are always 3 hours per day.

I've read your manual where you also suggest to use always 100% constraints whenever possible.

When you say to use 100% in this post you mean to set minimum days between activities = 1 day at 100 %?

The problem with this approach I think is that the same teacher has maybe another single hour of another course with the same student set so there is still the risk that he meets the same students too many hours (e.g. 4) in one day.

I was trying with 1+1+1+1.... because I was thinking that this way FET would have had more possibilities to solve the timetable and thus a faster computation but now I'm not sure anymore. I've also read the important tips section of documentation where the first tip suggests a third and different approach. I'm a bit confused.

By the way, when you say check that the timetable is still solvable how much time should i wait?
For example if FET solved the timetable in 3 minutes, than with the new constraint "Same day" how much extra time should I accomodate?

2 min 04 secs on an Intel Core i5-2520M CPU@2.50 Ghz 2.50Ghz

Ma con i criteri che dici non c'è il rischio che siano sempre i soliti ad avere i desiderata soddisfatti?

Ciao,
nella mia esperienza la difficoltà nasce quando raccolti tutti i vincoli come dici tu poi l'orario comunque non viene.
In questo caso bisogna cominciare a scegliere dei vincoli da rimuovere/rilassare per far tornare l'orario e nasce il problema di come farlo con equità/giustizia, inoltre non è sempre facile capire quali sono i desiderata che impediscono all'orario di venire generato.

Ad esempio quasi tutti i professori vorrebbero come giorno libero il sabato oppure il lunedì, ma a volte non ci sono abbastanza professori che lavorano in questi gg per tutte le classi della scuola e quindi è necessario cominciare a scegliere un professore e rimuovere il vincolo gg libero al sabato.

Se ci fosse una priorità almeno tra i desiderata degli insegnanti personalmente riuscirei a lavorare meglio, ad esempio se un professore di italiano mi dicesse che preferisce rinunciare alle 3 ore attaccate per il tema pur di avere il gg libero al sabato avrei già una bussola con cui orientarmi.

Maybe think about this:

I prefer to split an activity into max (number of days per week) and use 100% weight.
So activity 1 is fine.
I prefer to split activity 2 as 2+2+2+2+1
So in worst case there are 4 hours per day.

Now try if the timetable is still solvable.

If it is still solveable use constraint "same day" for the first subactivity of activity 1 (duration 2) and the last subactivity of activity 2 (duration 2).
So there are always 3 hours per day.

Thanks, this also could be useful but I think it is a bit complex for me.

The link is wrong.

Yes, your steps are correct, but define two activity tags and set teacher activity_tag_1 max 3 hours daily then teacher activity_tag_2 max 3 hours daily. So, different activity tags for different students sets.

Your approach is better for performance, but only if you don't add min days constraints.

Sorry here should be the right link:
http://lalescu.ro/liviu/fet/forum/index.php?topic=407.0;topicseen

I don't understand your example with the tags. If i do as you say I think that it could happen that there are three hours 1A and then two hours of 1A,1B in the same day and I don't want this. Could you please explain better?

I think this maybe similar or the same as an old post of mine;
http://lalescu.ro/liviu/fet/forum/index.php?topic=1502.0;topicseen

I think I can't use Teacher activity tag max hours daily because the teacher can do up to 5 hours daily, the problem is that she can't see the same students for more than 3 hours daily.

Let's suppose I have teacher T with
- an activity 1 in class 1A of 6 hours in 5 days and
- an activity 2 in classes 1A,1B of 9 hours in 5 days
with constraints
- I don't any class to see teacher T more than three hours daily
- I want at least 2 consecutive hours of activity 1 but I'm not interested in how al other hours get splitted/grouped

Is the following correct?

1) I split activity 1 as 2 +1+1+1+1 and activity 2 as 1+1+1+1+1+1+1+1+1
2) I avoid at all min days between activities
3) I set a TAG such as max3h for both activities
4) I use the constraint max hours daily with an activity tag for all students

My idea is that this could lead to more possible solutions than splitting activity 2 in 3 +2 +2 +1+1 but I'm not sure because on performance hints it's suggested to split the activities to match the number of working days.

Ciao a tutti,

non mi ricordo se fosse un argomento già trattato.

Per caso sapete se esiste un modulo/questionario da sottoporre ai docenti per raccogliere tutti i dati necessari in input a FET?
Secondo me gli insegnanti dovrebbero esprimere i vari vincoli con un'ordine di priorità in modo da poter eventualmente rilassare i vincoli che causano un orario impossibile.
Ad esempio per un insegnante che fa 18 ore o più alla settimana su 30:
1) 5 ore libere in un determinato giorno
2) non più di due ore buche
3) Una lezione da 3 ore attaccate senza intervallo per il TEMA

E' chiaro che in un caso come questo dopo aver esposto tutti i vincoli bisogna metterli in ordine di priorità per capire cosa è più importante.

Spesso ho notato che gli insegnanti fanno fatica ad esprimere tutti i loro desiderata e solo se messi di fronte a una domanda puntuale del tipo "preferisci A o B" sono in grado di esprimersi.

Hello,
this is maybe the third year that I use fet to generate the timetable for our high school. 
Every year it takes a bit of time to rember how to use it properly and this year I've a new idea.
I often split an activity of 6 hours in 5 days as 2 + 1 + 1 +1 and then I set at 95% min days between activities in order not to have more than 2 hours per day with the same teacher. I'm not interested in having 2 hours consecutive if they happen the same day except for the first activity that I set with a two hours duration by myself.
So wouldn't be easier for FET (and me) to avoid completely the min days between activities constraint and just to add a max hours daily for a teacher with a student set ?
Unfortunately some teacher has more than one activity with a student set so I think this would be not the same as "max hours daily for an activity".

Ciao!