combine break (Lunch) time with gaps

[Nagendra]

My time table becomes impossible when I make max gaps as "zero or one" per week. So, I decided to to go with max 2 gaps per week for all student sets. I have generated the timetable which looks like the attached.

I have a lunch break activity which is preferred to be placed in 6th or 7th periods. Now, what constraints I should use so that these gaps, if any, are always adjacent to a lunch break (or) it is in the 1st or last period of any day?

I don't think I can add a dummy activity (just like lunch) because, I don't know the number of gaps for any particular group (it can be 'zero', 'one', or 'two')....With this, my timetable will become perfect. 

Here, Lunch break is created by the combination of Subject: Lunch and activity Tag: Break.

[Liviu Lalescu]

You can add 2 dummy activities for each students subgroup, and decide yourself if it should be adjacent with a Break (so 100% 2 activities grouped) or preferred starting times first or last slots of each day.

You then impose max 0 gaps per week for every students set.

[Nagendra]

There are some groups where 39 slots out of 40 slots are occupied. I am getting error when I try to add 2 dummy activities (obviously)... There may be even some groups without a vacant slot. That's why I said I may not be able to add a dummy activity. So, my intention is to force the gap and lunch together, if at all there are any gaps. If there are no gaps, then I don't want to do anything for that students set.

Is there any way I can see the number of gaps (or atleast free slots) for each subgroup? So, I can write a program to add a dummy activity only for the groups with gaps.

For some years my student sub groups are individual roll numbers (they may be in thousands). So, do I need to add a dummy activity for each and every roll number independently? 

[Liviu Lalescu]

I think Volker wrote the statistics for gaps of students, see the HTML results.

Yes, for each subgroup 

[Nagendra]

I think Volker wrote the statistics for gaps of students, see the HTML results.

Yeah...In HTML it is...But in .csv it is not there.

Yes, for each subgroup 

Hmm, I can write a MATLAB code to create them (subjected to the availability of .csv of statistics). But I don't think it is feasible to have 1000's of addition activities just to avoid gaps.

I am leaving it as it is.....However, I impose the minimum gaps per week constraint on each year individually, instead of "all students". This way atleast I can reduce the gaps for some years. 

But, if there can be a way to add a constraint "minimum gaps between a 'GAP' and activity tag", it will solve my purpose. But, it doesn't make sense at all. 

[Liviu Lalescu]

But, if there can be a way to add a constraint "minimum gaps between a 'GAP' and activity tag", it will solve my purpose. But, it doesn't make sense at all. 

No, sorry, I cannot add this. Too difficult or impossible.