Author Topic: Why is my timetable not feasible?  (Read 425 times)

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Monte Stello

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Why is my timetable not feasible?
« on: January 05, 2017, 05:44:43 PM »
Hi,

I do not understand why this timetable is not feasible. Mainly, I have one subject (S4) where I have limited capacity and some new groups have to be split. Instead of 6 groups, I need 7 groups with group Culture 7 being made of some students from G1, G2 and G3. I do not understand why FET is failing because if I remove the group Culture 7, I can easily find a slot for the S4 activity.

Could you please help me on this topic?

Many thanks.

Volker Dirr

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Re: Why is my timetable not feasible?
« Reply #1 on: January 05, 2017, 05:53:21 PM »
But there is a detailed error report for your bug:
you have got only 24 free time slots, but Culture 7 need 25 slots.
so this is impossible.

you need to:
a) decrease the number of activities for Cultures 7
or
b) allow one more time slot.

since you didn't understood the bug yet, i suggest to do variant b). then generate and view the timetable. i hope you will understand then why you need 25 time slots.

Monte Stello

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Re: Why is my timetable not feasible?
« Reply #2 on: January 06, 2017, 03:42:28 AM »
Thank you for your answer. I understood the error message but I am confused because I am able to solve the timetable by hand. I have removed the subgroup "Culture 7" (and its activity S4). Then FET can solve easily the timetable. I am attaching a solution I am getting (with locked time slots).

If you look at the attached file, you realise you can find easily a time slot for a "Culture 7" subgroup (made of students from G1, G2 and G3) on Subject S4 with Teacher t4: 27/02 PM, 15/03 AM and 16/03 AM+PM timeslots are not used by anybody.

Could you please explain me why I am not able to have FET finding a solution?

Many thanks.

Volker Dirr

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Re: Why is my timetable not feasible?
« Reply #3 on: January 06, 2017, 05:36:52 AM »
Sorry, but your manual found solution is wrong.
Why? Because you want to have "Cultures 7" in G1 and G2.
But now have a look at your timetable. There are a lot of activites from set G1 and G2 at the same time now. For example on 02/03.
G1 has got S6 - t6
G2 has got S1 - t1
That is impossible if you add "Cultures 7" into G1 and G2, because it mean those activities can't be at the same time.

Your manual solution has got a similar bug on 07/03.

If you say that G1 and G2 are allowed at the same time, then you totally misunderstood the idea of a subgroup. In that case you should read the following link to understand it better:
http://www.timetabling.de/manual/FET-manual.en.html#id_12
« Last Edit: January 06, 2017, 05:45:22 AM by Volker Dirr »

Volker Dirr

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Re: Why is my timetable not feasible?
« Reply #4 on: January 06, 2017, 11:31:15 AM »
Reading your messages again, i saw this:
Quote
Culture 7 being made of some students from G1, G2 and G3.

I also saw you use "G1" and "Y1 Culture 1" the activities. that is "stupid" since both are the same!

So i guess you misunderstood how to make subgroups.
Please check the attached file and check how i done subgroups for G1, G2, G3 and Cultures7.

Or, instead of "Cultures7" just add G1, G2 and G3 into the activity.

I fear a bit that your students set is not finished yet. You should use the automatic split feature, since it will be more complicated if you have more of those "problems".
Or import the students structure by csv.
« Last Edit: January 06, 2017, 11:34:03 AM by Volker Dirr »

Monte Stello

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Re: Why is my timetable not feasible?
« Reply #5 on: January 06, 2017, 03:56:42 PM »
Thank you for the time you spent on my issue. You were right I misunderstood how group/subgroup work. I think I have managed to make it right now.

Thanks again.