Hi Christian,
I know that optional tasks cannot have their start and end times pruned,
however, their mandatory flag can be marked false.
It seems that the two commented-out lines would discard the optional
tasks when it detects that they cannot be mandatory.
Very similar code can be found in detectable.hpp:
for (int i=n; i--; )
if (t[i].mandatory()) {
GECODE_ME_CHECK(t[i].est(home,est[i]));
} else if (est[i] > t[i].lst()) {
GECODE_ME_CHECK(t[i].excluded(home));
t[i].cancel(home,p,Int::PC_INT_BND); t[i]=t[--n];
}
Kind regards,
Bauke
On 02/17/2014 03:59 PM, Christian Schulte wrote:
> Hi Bauke,
>
> No, they can't, in the current setup this would make the propagator
> incorrect. The reasoning is as follows: while the task is still optional,
> one is not allowed to prune anything. The reason why the code still lingers
> on as a comment is that if one introduces an additional wrapper in forms of
> task variables, this kind of reasoing could be used.
>
> Best
> Christian
>
> --
> Christian Schulte, Professor of Computer Science, KTH,
> www.ict.kth.se/~cschulte/
>
>
> -----Original Message-----
> From: users-boun...@gecode.org [mailto:users-boun...@gecode.org] On Behalf
> Of Conijn, B.J.
> Sent: Friday, February 14, 2014 2:08 PM
> To: users@gecode.org
> Subject: [gecode-users] Unary constraint not-first-not-last propagation does
> not cancel optional tasks
>
> Hi,
>
> In not-first-not-last.hpp I found the following piece of code and I was
> wondering why those two lines have been commented out. While running the
> tests with those two lines included, those lines get executed and the test
> still succeeds. Can those two lines be safely included?
>
> if (t[i].mandatory()) {
> GECODE_ME_CHECK(t[i].lct(home,lct[i]));
> } else if (lct[i] < t[i].ect()) {
> // GECODE_ME_CHECK(t[i].excluded(home));
> // t[i].cancel(home,p); t[i]=t[--n];
> }
>
> Kind regards,
>
> Bauke
>
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