[gecode-users] Limiting some combinations of variables

[Conrad Drescher]

Hi,

2013/6/6 Pascal Francq (Mailing lists) <mailing-list at francq.info>

> Hi,
> I have a question regarding how to avoid some combinations of variables
> to test. I give here a simple example:
> 1. I have four IntVar a,b,c and d.
>

Gecode-matters aside I think that this


> 2. I want to allow a=2*b=2*c only if a==1 and d==0.
> If have try to encode this constraint with a code that looks like:
>         BoolVar tmp;
>

doesn't say the same as this:


>         tmp=expr(home,(a!=1)&&(a==2*b)&&(a==2*c)&&(d==0));
>         rel(home,!tmp);
>

If I understand your 2. correctly it says:

neg (a = 2*b /\ a = 2*c /\ (a != 1 \/ d != 0))

Hence I think tmp should be something like

expr(home,(a==2*b)&&(a==2*c)&&((a!=1)||(d!=0))

HTH
Conrad


> But it seems that it does not try the only combination allowed.
> Is this the correct way ?
> Thanks.
> --
> Dr. Pascal Francq
> Belgium
>
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