[gecode-users] Incremental constraints

[Christian Schulte]

Hi Malcolm,

yes you can add constraints dynamically. Actually you can add anytime! The
only thing you need is to have access to the space you want to add
constraints to.

One way to get started would be to branch only over the subset of the
variables. Then when search stops (it will stop if the branching is done),
you can add more constraints and additional branchings.

Cheers
Christian

--
Christian Schulte, www.ict.kth.se/~cschulte/


-----Original Message-----
From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
Of Malcolm Ryan
Sent: Monday, August 25, 2008 8:25 AM
To: gecode list
Subject: [gecode-users] Incremental constraints

I'm having efficiency problems with my constraint system. It is slow
compared to a standard search algorithm with much more limited
deductive ability. I think that too much time is being spent
propagating constraints in ways that are ultimately not improving the
search.

Rather than abandon CSPs completely, I'd like to experiment with
modulating the amount of propagation to see if there is some point at
which it becomes advantageous. Is there any generic way to do this? If
I remove constraints completely, it will effect the correctness of my
solution, which I don't want to do. I just want to delay constraint
checking/propagation.

One way that occurs to me would be to add constraints incrementally,
during the search. Could Gecode handle this? If so, which phase of the
search process should it occur in? I'm guessing that it should be part
of commmit(). Would that be appropriate?

Thanks,

Malcolm

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