A teacher works in an hourly interval max days....

[Chafik Graiguer]

what is the use of this constraints:
A teachar works in an hourly interval max days per week

Can it be used, on a standart non customised FET version, to obtain : teacher works only a helf day ( either morning or afternoon) ?

[Liviu Lalescu]

At some universities or schools, teachers would like to work at the last hours say from 20 to 22) only 2 (or 1) times per week, so they don't get exhausted in these periods.

No, you cannot use this constraint for your situation (I am tired now, please think about it and if I am wrong correct me).

[nouvakis]

This option doesn't seem to work.
I don't know if it worked with previous versions of FET.

It would be a nice feature !

[Volker Dirr]

Please attach (or sent by email) a sample file where we can check/see that the constraint failed.

[nouvakis]

I tried to a real timetable. I also tried with only one teacher and one lesson.

I've attached the second one.

[Volker Dirr]

ah. ok. now i understand.

the fet constraint work correct. you request is a bit different. it can't be used that way. (you need to add come more "works in an hourly interval max days per week"-constraint and that constraints must be connected with an logical OR. But that is not possible with fet. So you still need to use the customised FET version.)

[mbarsan]

Hi. In Italy we have a working week of 6 days and we let every teacher to chose one free day.
So every teacher works only 5 days over 6.

We adopted a trick to let FET to chose a free day, when a teacher ask a free one from a selection of 2 (or more) days.

Applying this trick to your example seems to give a solution.
To get the solution I presumed that your working day is 4 hours in the morning and 3 hours in the afternoon.
I added a dummy hour to 7 to have exactly 4 hours for half a day.

No student may work in that eighth hour.

I added an activity divided in 5 subactivities of 4 hours each - teacher1, no student - , with 1 day between subactivities at 100%.
This activity may start at first or at fifth hour every day. Subject name is "HalfDayFree"...
The teacher will be constrained to work max 8 hours per day (instead of 4). We have 4 hours dummy.

We obtain attached file.

[nouvakis]

I added an activity divided in 5 subactivities of 4 hours each - teacher1, no student - , with 1 day between subactivities at 100%.
This activity may start at first or at fifth hour every day. Subject name is "HalfDayFree"...
The teacher will be constrained to work max 8 hours per day (instead of 4). We have 4 hours dummy.

We obtain attached file.

Thanks a lot. Nice trick !!!

Proposal: Tricks like this should be collected in a help file !!!

[Volker Dirr]

Thanks a lot. Nice trick !!!

Proposal: Tricks like this should be collected in a help file !!!

Dummy tricks are already collected in the manual ("It's allowed to add pseudo activities. Pseudo activities doesn't include a students set or a teachers set. Sounds stupid, but they are useful to care about some constraints. Compare sections Not available teachers, students or rooms & breaks, Gaps, Preferred time(s) and Preferred room(s).").

But maybe i should add more examples.

But don't forget that these dummy tricks has also disadvantages:
They effect not available times, gaps, rooms, min n hours constraint und max x hours constraints.
In this case it also work only correct if morning has as many hours as the evening.

[nouvakis]

Is it possible to explain how the "A teachar works in an hourly interval max days per week" constraint works ?

[Volker Dirr]

You set number of days=5. So it has no effect, because your week has also 5 days.
if you reduce it down to 4 (and keep hours from 1-4), then the teacher will teach max 4 days in the morning.
don't forget that the constraint tells you nothing about the afternoon. so it might happen that the teacher work at no afternoon, but it might also happen that he work at every afternoon.