I have noted that at times,a file may take 10 minutes to generate.If i add a constraint and generate and realize that there was no need of it,upon stopping the generation and removing that constraint and telling it to generate,it ends up taking longer than the 10 minutes it had previously.Why does this happen?
It is normal, because:
Main reason: The generation is semi-random. It depends on luck. We have at least 2 files (CONCORDIA in Namibia and FS-difficult in Romania) which generally take a few minutes, but may take 5 hours.
Another possible reason: consider if you lock a timetable. It has more constraints, but generates instantly.
So as long as the constraints are manageable, speed lies on luck
Yes, a bit. There are some 'more random' files and 'more constant' files (like the German example). FET is a heuristic for an unsolved problem.
I understand
If you want to know some more about the speed, then maybe whatch some of my videos:
https://www.youtube.com/watch?v=XxfJAaPRmxo (Speed up by CPU)
https://www.youtube.com/watch?v=MVt0Yb9y8xc (Speed up by Multi Core)
https://www.youtube.com/watch?v=DejTeNM0T6I (Speed up by software)
https://www.youtube.com/watch?v=nEmsf_-f6P4 (Speed up by software)
https://www.youtube.com/watch?v=rl5N_ZyBB6A (Speed up by time limit)
Will have a look.Thanks