[gecode-users] model with float variables sometimes hangs during search

[Vincent Barichard]

Hi,

My first thought is that it is a slow convergency process. It often occurs
when linear constraints are involved with particular coefficients. A first
clue may be the number of propagations done in one call to Space::status().
For the cases where the search ends (with a big amount of time) you may
check the number of propagations done. If it is abnormally huge, it's
probably a slow convergence. Without digging in the model and trace the
search, I can't say much more. Sorry ....

Regards,
Vincent

2015-04-15 16:05 GMT+02:00 Christian Schulte <cschulte at kth.se>:

> Hi,
>
>
>
> This could be a feature and not a bug in that constraint propagation is
> just very slow to converge. For floating point numbers there is this risk.
>
>
>
> I would not know what to suggest without knowing how the model looks like
> but I am also not an expert in floating point. Vincent: do you have an idea?
>
>
>
> Cheers
>
> Christian
>
>
>
> --
>
> Christian Schulte, www.gecode.org/~schulte
>
> Professor of Computer Science, KTH, cschulte at kth.se
>
> Expert Researcher, SICS, cschulte at sics.se
>
>
>
> *From:* users-bounces at gecode.org [mailto:users-bounces at gecode.org] *On
> Behalf Of *Kurt Van Den Branden
> *Sent:* Wednesday, April 15, 2015 4:00 PM
> *To:* users at gecode.org
> *Subject:* [gecode-users] model with float variables sometimes hangs
> during search
>
>
>
> hi,
>
> I have a Gecode model that uses float variables.
> I use a BAB searchengine with a Search::TimeStop object to interrupt the
> search when it takes too long.
>
> I noticed that when the model is created with certain parameters, the
> search isn't interrupted at the requested timelimit.
> it either continues a lot longer than allowed, or it doesn't stop at all.
>
> in these cases, the debugger shows that it's the method Space::status that
> doesn't return sometimes.
> it keeps on propagating and never stops.
>
> I haven't been able to reproduce this with a limited test model yet.
>
> Does anybody have tips on what could cause this problem?
>
> Kind Regards,
>
> *Kurt Van Den Branden | Agfa Graphics*
>



-- 
Vincent Barichard         Université d'Angers (LERIA)
Tel:  02 41 73 52 06      Département Informatique
Fax: 02 41 73 50 73      H203
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