A free day but never on Monday

[gesamtschule]

We have the wish form on teacher, that the only want to work 4 days a week. For her it was unimportant at which day she has a free day, except that the definitely want to work on Monday. Any ideas how to realize this?

[Liviu Lalescu]

The easiest way, but not perfect: choose an activity of this teacher and constrain it to be on Monday. You might obtain a solution - but in some cases you are excluding some solutions.

It might work, though.

[gesamtschule]

This was our solution to, because we have only one teacher for which this becomes necessary this is indeed a solution which doesn't made the solution room to small.
But it would be made the program easier to use if it become possible to define such constraint directly.

[Liviu Lalescu]

It would be difficult and I cannot express this constraint into words, to give it a FET notation (I mean how to name the new constraint).

[gesamtschule]

Well you could create a constraint preferred time for a teacher, where we could define the Monday, analog to preferred time for an activity. This gives fet more freedom to find a solution.
But if this become difficult to realize, we must use your idea to fix an activity on Monday.

[Liviu Lalescu]

Well you could create a constraint preferred time for a teacher, where we could define the Monday, analog to preferred time for an activity. This gives fet more freedom to find a solution.
But if this become difficult to realize, we must use your idea to fix an activity on Monday.

It is not the same. To put an activity on Monday is simple, to put any activity from a set on Monday is not easy.

Maybe you could also try with making a not available day for this teacher, your choice: Tuesday, Wed. or Thu or Fri.

[Volker Dirr]

I will be easy if that teacher teach an activity that is splitted into 4 period per week and min n day constraint.
Just use a constraint that one out of that subactivities must be scheduled on Monday.


If that teacher have activities with less then 4 periods per week, then try it with an activity that have duration 3.

[Liviu Lalescu]

I will be easy if that teacher teach an activity that is splitted into 4 period per week and min n day constraint.
Just use a constraint that one out of that subactivities must be scheduled on Monday.


If that teacher have activities with less then 4 periods per week, then try it with an activity that have duration 3.

Yes, exactly, good suggestion. It is the same for FET which component you select, from 4 components. The algo has the same speed.

Also, you might choose a day to make a teacher not available (not nice solution).

[Chafik Graiguer]

-Define a dummy activity for this teacher: Ad
- Define Maximum days per wwk for this teacher = 4
-Define constraint that Ad must be scheduled on Monday
Since activity Ad will be scheduled on monday, FET has no other choice than putting additional activities on monday also
then FET will look for 3 other day !!!

This assume that (number of REAL activities) + (Ad) doesnot exceed Maximum hours daily for this teacher
For example,  I can constraint this dummy activity  into lunch break for example

[Liviu Lalescu]

-Define a dummy activity for this teacher: Ad
- Define Maximum days per wwk for this teacher = 4
-Define constraint that Ad must be scheduled on Monday
Since activity Ad will be scheduled on monday, FET has no other choice than putting additional activities on monday also
then FET will look for 3 other day !!!

This assume that (number of REAL activities) + (Ad) doesnot exceed Maximum periods per day for this teacher
For example,  I can constraint this dummy activity  into lunch break for example

Brilliant! Congrats on nice tricks!

Maybe he also needs to add min hours daily constraint.

But you cannot put this activity into Lunch break, because no activity can be there. But as a last resort he can increase number of hours per day and make other slots not available as needed.

[Volker Dirr]

The dummy activity trick is also nice, but be careful:
1. If that teacher teach only a few hours per week, then he might get a gaps problem. Solution: just add that dummy activity not into a special slot, just use constraint preferd day.
2. You might get problems if the teacher teach many hours per week and if you also have a max hours per day constraint.

[Chafik Graiguer]

But you cannot put this activity into Lunch break, because no activity can be there. .

I meant a lunch break witch is defined only for students or rooms not fir teachers
This is what actualy I did, when I tried to tweak official FET version settings, I defined lunch break for rooms only, that is making them unavailable!!

2. You might get problems if the teacher teach many hours per week and if you also have a max hours per day constraint.

Yes
We need to know exactly how much hours  per week teacher has

[gesamtschule]

Well my experience with dummy activities are really ambivalent. You could solve a lot of problems with it, but you get mostly new ones.  In this case the teacher has not very much hours a week (This is a normal situation at this school). So we defined that every teacher must have at least 2 hours a day. So in this case you must for the Monday define that it must be at least 3 hours. So the number of constraints increase rapidly.

Never the less I respect that Liviu said it is not easy to implement - so we must live with the workarounds.  I prefer to start in such a case a detailed analysis and then use one of the suggested solutions.

[Volker Dirr]

What is about the subactivity trick? Or is that teacher only teaching activities with less then 4 periods?

[gesamtschule]

Good hint, this could work. We will try it next time. It doesn't work in every situation but I hope in such special case.

Just to make it clear: I like FET and I'm really glad to work with it. All suggestions are send to make a good product better.