Assigning "no room"

[aliponte]

I'm timetabling with a good commercial program, but I'm always openminded for something new in the field. That's why I'm giving FET a try now. With the program I've been using so far I make extensive use of pseudoactivities. These are powerful means to solve a lot of difficult constraints.

In FET I define a pseudoactivity for a group "A". This group a certain home room is assigned to. What can I do to override this home room by an "empty room" when group "A" is doing the pseudoactivity? There are constraints provided by FET to assign a specific room for every specific activity, but there seems to be no choice to assign "no room" to the activity.

Thank you for responding

alipont

[Volker Dirr]

you don't need to enter a pseudo activity for this.
you need to enter a "pseudo" room. (i wrote "pseudo", because why don't you just add the real room where they are, even the room is not at you school.)
then you can use a space constraint for this activity.

[Liviu Lalescu]

you don't need to enter a pseudo activity for this.
you need to enter a "pseudo" room. (i wrote "pseudo", because why don't you just add the real room where they are, even the room is not at you school.)
then you can use a space constraint for this activity.

Yes, do it like Volker suggests (because preferred room is more powerful than home room - preferred room(s) overrides home room(s) ), or like this: for this pseudo activity, add another dummy students set. This way, FET will not consider a home room (because it has more than one students sets).

What other program are you using? (I think they do not mind if you write here about it, and maybe also you could make a comparison and let us know).

[aliponte]

@Liviu (Last question)
About 20 years ago I used "UNTIS" by Gruber & Petters (Stockerau, Austria), which was a DOS-program then. Now I'm using "SPM" by Dietmar Klinger, Nürnberg (www.dklinger.de). This program is on the market since 1995 and meets especially the needs of the german "Kollegstufe" (a system, where a student chooses a set of courses out of a set of available courses).

[aliponte]

Excuse me, I didn't explain, why I need these pseudo activities.

Once a week "year A" (which is a class of 30 students in fact) has to attend 2 lessons in the afternoon, but not twice a week 1 lesson. Within the allowed frame of timetable places for that year A, I place pseudo activities with time constraints, that fix their starting times in the afternoon. I need 4 pseudo activities to cover 4 afternoons leaving 1 afternoon open. Since the starting time of each pseudo activity can float from monday afternoon to friday afternoon there is one open and _not_ defined afternoon that can float over the week. That was my intension.

Of course during these pseudo activities year A doesn't need a room. It would be unwise to declare the home room of year A occupied during pseudo activities. So I was looking for some means to override the home room reservation and found the constraint "An activity has a preferred room". But unfortunately I could not choose what I wanted to: "No room".

So I created a set of pseudo rooms each one to be assigned to a pseudo activity. This was the only approach I found so far. But wouldn't it be more obvious if there exists the option "no room"?

aliponte

[Liviu Lalescu]

Excuse me, I didn't explain, why I need these pseudo activities.

Once a week "year A" (which is a class of 30 students in fact) has to attend 2 lessons in the afternoon, but not twice a week 1 lesson. Within the allowed frame of timetable places for that year A, I place pseudo activities with time constraints, that fix their starting times in the afternoon. I need 4 pseudo activities to cover 4 afternoons leaving 1 afternoon open. Since the starting time of each pseudo activity can float from monday afternoon to friday afternoon there is one open and _not_ defined afternoon that can float over the week. That was my intension.

I think you are complicating things uselessly. You can a duration 2 activity, split into only 1, and add a constraint for it (to end students' day or preferred starting times or preferred time slots). Why adding 4 activities?

Of course during these pseudo activities year A doesn't need a room. It would be unwise to declare the home room of year A occupied during pseudo activities. So I was looking for some means to override the home room reservation and found the constraint "An activity has a preferred room". But unfortunately I could not choose what I wanted to: "No room".

So I created a set of pseudo rooms each one to be assigned to a pseudo activity. This was the only approach I found so far. But wouldn't it be more obvious if there exists the option "no room"?
aliponte

You are right, I never considered this possibility. But I told you another possible trick: add more teachers or students sets, and the home room is neglected (home room only matters if activity has only one teacher and only one student set). Or you can use preferred room and dummy rooms, as you like better.

[aliponte]

I think you are complicating things uselessly. You can a duration 2 activity, split into only 1, and add a constraint for it (to end students' day or preferred starting times or preferred time slots). Why adding 4 activities?

Not quite as useless as you might think. Sure, I could declare in advance which activity has to be in the afternoon, and then I choose the appropriate time constraint for it. But I want to leave it to the program which activity that is. The program is to decide: what is the best activity for the afternoon and the program is to decide which is the best afternoon in the week. My experience is: The less restrictions, the better the timetables.

[Liviu Lalescu]

I think you are complicating things uselessly. You can a duration 2 activity, split into only 1, and add a constraint for it (to end students' day or preferred starting times or preferred time slots). Why adding 4 activities?

Not quite as useless as you might think. Sure, I could declare in advance which activity has to be in the afternoon, and then I choose the appropriate time constraint for it. But I want to leave it to the program which activity that is. The program is to decide: what is the best activity for the afternoon and the program is to decide which is the best afternoon in the week. My experience is: The less restrictions, the better the timetables.

I am sorry! Now I understood. You don't know the activity to place at that interval. Yes, of course it is better to leave more options, the timetable is easier to find.

Another solution (I like it more than your's): add constraint students interval max days per week, interval afternoon, max days 1. Please let me know if it works (if you decide to test this one).