Hi,
David Rijsman wrote:
> you are absolutely right, this extension is very useful for cyclical rosters.
> Should not be very hard to enable in the current implementation, basically
> changing the check at posting the constraint. I see if I can do this and see
> if this gets accepted?
The question is whether the algorithm is still correctly reporting fixpoints
when the variable array contains variables more than once. I don't know the
algorithm well enough to tell from just a quick glance. Usually, the test
suite is pretty good at detecting these cases, so you could simply remove the
check in the post function and write a test to see if anything goes wrong.
If shared variables are indeed a problem for the algorithm, you can use unshare
to replace all shared variables with fresh variables (linked to the originals
by equality constraints).
Cheers,
Guido
>
> David
>
>>>>
> From: Kish Shen <[email protected]>
> To: <[email protected]>
> Date: 8/19/2010 2:03 AM
> Subject: [gecode-users] sequence constraint: variable occurring multiply
>
> Hi,
>
> I have another question about the sequence constraint: exception
> ArumentSame is thrown if a variable occurs more than once. Should this
> exception be thrown? I can see that it does not make sense for a
> variable to occur in a subsequence of q variables, but if the 'distance'
> between the same variable > q, i.e. it cannot occur multiply in the same
> subsequence, should this be allowed? Can the implemented algorithm deal
> with this?
>
> There are useful cases for variables to occur multiply, the simplest is
> a cycle, e.g. say for the following variables
>
> x1,x2,x3,x4,x5
>
> and a cycle would be
>
> x1,x2,x3,x4,x5,x1,x2,....
>
> such cycle could be used for a schedule that repeats.
>
> Cheers,
>
> Kish
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--
Guido Tack, http://people.cs.kuleuven.be/~guido.tack/
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