[gecode-users] Unary: Allow for negative durations when task is not mandatory

[Andrea Peano]

Hi Roberto,
thank you very much. I'm pretty sure that it's close enough to my needs!

I'll try it asap :)

Thanks,
Andrea

On Fri, Nov 1, 2013 at 9:45 AM, Roberto Castaneda Lozano <rcas at kth.se>wrote:

> Hi Andrea,
>
> Interestingly enough I implemented for my own purposes a similar
> generalization to nooverlap a year ago, see the attachment.
>
> Best regards,
>
> Roberto
>
> From: users-bounces at gecode.org [users-bounces at gecode.org] on behalf of
> Andrea Peano [andrea.peano at unife.it]
> Sent: Thursday, October 31, 2013 12:50
> To: Christian Schulte
> Cc: users at gecode.org
> Subject: Re: [gecode-users] Unary: Allow for negative durations when task
> is not mandatory
>
> Yes, sure it's useful, thank you.
> I'm just wondering whether a modification of the unary might be more
> efficient or not.
> In such a case, I could modify the source files of Gecode, by adding
> another (modified) unary constraint, otherwise... should I write an
> user-defined propagator?
>
> I've the same doubt regarding the nooverlap, I'd like to achieve a
> generalization of it.
> In this generalization rectangles of the same "group" can overlap
> eachother, but they cannot overlap other rectangles of other groups.
> So the new nooverlap will take in input an IntArgs array which contains
> the group IDs.
>
> In your guide I read:
> "The constraints [nooverlap] are implemented by a naive propagator
> (considering pairwise no-
> overlap between rectangles including constructive disjunction, see also
> GCCAT: diffn),
> this will change in the future. "
>
> I could add a condition within the implementation of the nooverlap, that
> checks if the two rectangles belong to two different groups. Is it right?
>
> Do you have any suggestion?
>
> Thank you,
> Andrea
>
> On Wed, Oct 30, 2013 at 1:05 PM, Christian Schulte
> <cschulte at kth.se> wrote:
>
> Hi,
>
> There is a generic trick for situations like this: you introduce new
> variables tend', tstart' and tdur' and only enforce that they are equal to
> tend, tstart,
>  tdur respectively when the Boolean variable is 1. That means if the
> Boolean variable is 0, the new variables can have whatever value.
>
> Hope that helps
> Christian
>
> --
> Christian Schulte, Professor of Computer Science, KTH,
>
> www.ict.kth.se/~cschulte/
>
>
> From:
>
> users-bounces at gecode.org [mailto:users-bounces at gecode.org]
> On Behalf Of Andrea Peano
>
> Sent: Tuesday, October 29, 2013 10:21 AM
>
> To:
> users at gecode.org
>
> Subject: [gecode-users] Unary: Allow for negative durations when task is
> not mandatory
>
>
> Hello all,
>
> I would modify the unary constraint in order to allow negative durations
> (tend<tstart) when the boolvar m (mandatory) is 0.
>
> Is there an easy way to do this?
>
> Thank you,
>
> Andrea
>
> --
>
>
>
>
> Andrea Peano - PhD student
>
>
> Department of Engineering - University of Ferrara
> Tel: +39 0532 97 4827
>
>
>
>
>


-- 

Andrea Peano - PhD student
Department of Engineering - University of Ferrara
Tel: +39 0532 97 4827
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