Very difficult file needing your help

[Liviu Lalescu]

Also, you have 1 'group activities in initial order' item in your latest file - is it correct?

[yush]

Please consider that if you increase the duration of these EN activities, you need to assure the affected constraints are correct - like preferred times, occupy min/max, not available.

Yes. The only affected time constraints are activities with the same time, which G1 and G2 are two groups. I've made sure to change all of them the same way. Also is min days between. I've also thought about this one. So, it should be OK.

See the attached photo for my "FET farm". This might be the most number of simultaneous FET runs you have ever seen!

[yush]

Also, you have 1 'group activities in initial order' item in your latest file - is it correct?

Yes. It is an activity that need to be at the same time as another group. It is two activities of 4+4 to coincide with another group of 4+4+4+4, so I don't want to fix it using the same start time constraint. I ended up using group of activities having max timeslot to achieve the overlap that I want. Thus, I want to put them together in the initial order.

[Liviu Lalescu]

Oh, wow!

[yush]

I was wondering how much computing I was doing comparing to mining bitcoin!

[Liviu Lalescu]

Also, you have 1 'group activities in initial order' item in your latest file - is it correct?

Yes. It is an activity that need to be at the same time as another group. It is two activities of 4+4 to coincide with another group of 4+4+4+4, so I don't want to fix it using the same start time constraint. I ended up using group of activities having max timeslot to achieve the overlap that I want. Thus, I want to put them together in the initial order.

I think in this case the 'group activities' might be too strong. But it cannot hurt too much.

[yush]

The most updated FET file to run.

[Liviu Lalescu]

OK, I will see it.

I think it is useless from me to try your file blindly. I will try to understand it and learn something from this situation. I should also try some other approaches.

So, for the start, I might try to put all the activities of year 1 at the end.

[yush]

I think FET's default ordering is doing a great job. I am sure if you put all Yr=1 to the end, it will get too difficult. Somehow, letting it run as default. Once it up to 1100+ with just yr=1 left, it often get stuck. Stop it, unlock all yr=1, it might get a result in matters of minutes.

[yush]

I don't know how FET decide to "back track" when it faces a difficult activities. Does it back track in reverse order of the initial order? If my manual unlocking method has any merit, it means that we might want to back track according to the "connectedness" of the activities. For example, if I am stuck at place order #1074, which is activity id#909, which is a Yr2 chemistry class 2A. Perhaps we should look at all the classes that is "closet" to 2A, meaning ther other 2A classes, and since 2A is often block with other yr=2 classes... in other word, we should unlock all the yr=2 classes that has already been placed and try again... just like my manual process.

[Liviu Lalescu]

Please see: https://lalescu.ro/liviu/fet/doc/en/generation-algorithm-description.html

The essence: FET will displace the conflicting activities for the current activity, which means either same students set, same teacher, or other conflict.

Are the preferred times constraints of the activities in your file needed, or you try to obtain some other features?

[yush]

Please see: https://lalescu.ro/liviu/fet/doc/en/generation-algorithm-description.html

The essence: FET will displace the conflicting activities for the current activity, which means either same students set, same teacher, or other conflict.

Are the preferred times constraints of the activities in your file needed, or you try to obtain some other features?

What kind of preferred time constraints are you referring to? There should be no preferred starting time constraints.

[Liviu Lalescu]

There are two sections of activities preferred times. See the two attached screenshots (one to this post, the second one in my next post).

[Liviu Lalescu]

And the next screenshot.

[yush]

They are in theory not necessary. What they do is the following:
- 45 minutes (each "Hour" is actually 15 minutes slots) will always start the day
- 60 minutes will always follow a 45 minutes class in the morning (before 10:30)
- or a 45 minutes following a 45 minutes is also possible
- plus a few variation for activities of 30 minutes or 75 minutes

The result (or desired result) is give the morning more structure so there will never be activities takes up unnecessary space. Imagine a 60 minutes class being placed at 9:00 am, the 15 minutes before or the 30 minutes after became almost unusable. Also, with this structure, there will never be overlapping activities in the morning, making classroom allocation much easier as everything is swappable.

The afternoon (after 12:45 for Y1,2 and after 1:00 pm for yr3,4) is more complicated. But I limit the possible times for activities with different duration to achieve what I described above.

So, in theory, 100% not necessary. I have some debate myself if they are useful, but so far they seems to allow me to get better results.

You can disable all of them to see the effect.