[gecode-users] IIS using undoing

[Max Ostrowski]

Hello,

i want to compute an "Irreducible Infeasible Set" (IIS) and some derivatives.
This means, given a set of contraints C that are infeasible i want to find the source of infeasibility.
I'm satisfied with a rather small (but not necessarily optimal) and fast approach.
A simple way of doing this would now be, trying to remove all single constraints from the set C and see if it is still infeasible. If yes, we can remove the constraint from the set.
In Gecode i could do this using a lot of copies of the Space, always posting the constraints again.
Instead of posting them again i could also use reified constraints and set all but one to true.
But here i also have to copy the space, as i can not ? undo the setting of a variable.
So is there a clever way of doing this abusing the Gecode SearchEngine ? (what i understood from the manual there is undoing instead of copying at some points).



The same thing i wanna do with a similar set C and a reified constraint x.
I wanna find the minimal (small) subset of C that the reified constraint x is still decided (true or false does not matter).


Thanks in advance for your proposals.

Best,
Max

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