As a follow up to my previous post on this, then from the reference
documentation, for
count(home, x, y, IRT_EQ, z)
where y and z are int, then there is only one consistency level
supported, and it is not domain consistent.
We have a rostering program (originally written for our ic solvder),
which I used to test the Gecode interface, and it uses count
constraints, and changing the consistency level affected the execution
times significantly for certasin problem instances. I took a look again
at the code, and the count constraints are with y and z being integers.
(the execution times are faster with ICL_BND than ICL_DOM)
The count single vsalue constraint is posted to Gecode using only one
propagator, the version with y and z being IntVar (and if they are
integers, they are posted as IntVar with a singleton domain). This is
done for all constraints that have variants that accept both IntVar and
int, as this avoid me having to write a lot of code to distinguish the
argument types, and I remember asking about this here a while ago and I
think Chirstian said that Gecode will figure out the best propagator to
use for the argument.
So my questions are: is the propagator posted the one with y and z being
int? If so, is there more than consistency level for the propagator, as
my result seem to suggest? The difference is very significant, e.g. for
one instance:
ICL_BND: 0.73s ICL_DOM: 198s
the ICL_BND times are more than 100 times faster, and the only
difference between the two runs are the count constraint posted with
ICL_BND rather than ICL_DOM (running on the same machine, of course).
Cheers,
Kish
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