[Scip] Determinism + attachment

[Timo Berthold]

Hi all.

Sorry for the double post!
For some nondeterministic reason I forgot to attach the settings file.

Bye, Timo



Am Monday 19 October 2009 17:07:09 schrieb Timo Berthold:
> Hi Alejandro.
>
> I played a little bit with your instance.
> Indeed, you need a lot of B&B nodes for this small number of variables and
> the root LP optimum is quite far away from the integer optimum. By the way,
> Cplex 12 also takes 300'000 nodes to prove optimality.
>
> The attached settings file proved to work well (on my desktop, using
> SCIP-1.2). It consists of settings/heuristics/aggressive.set,
> settings/cuts/aggressive.set plus some changes to perform conflict based
> restarts. In particular, the parameter conflict/restartnum is interesting
> as it determines when SCIP should abort and restart the search.
>
> Best, Timo
>
> Am Monday 19 October 2009 14:17:51 schrieb Alejandro Burzyn:
> > Ok, thank you again, recently I've found what the difference was between
> > the runs: I had changed the SCIP version from 1.1 to 1.2. In the attach
> > I've put the lp problem, and the stats of the runs of both versions of
> > scip (precompiled binary for windows with soplex in both cases, default
> > settings). The runs were made on an athlon xp 1.8 ghz, with 1 gb ram. I
> > think the principal difference is in the root cuts, but I don't know if I
> > should keep with 1.1 or tune 1.2 a little. I'll be grateful for any
> > advice. Thank you very much,
> > Alejandro
> >
> >
> >
> > --- El lun 19-oct-09, Tobias Achterberg <achterberg at zib.de> escribió:
> >
> > De: Tobias Achterberg <achterberg at zib.de>
> >
> >
> >
> > Asunto: Re: [Scip] Determinism
> > A: "Alejandro Burzyn" <aleburzyn at yahoo.com>
> > Cc: scip at zib.de
> > Fecha: lunes, 19 octubre, 2009, 6:30 am
> >
> > Alejandro Burzyn wrote:
> > > Thank you all for your answers, I think I've made a mistake somewhere
> > > with the lp
> > > (I think I've modified it somewhere between runs). However, I did test
> > > on different computers
> > > with same lp and same binary, and there I saw differences in stats no
> > > related to time, is this behaviour expected?
> >
> > Yes, if you run SCIP on different machines or on different operating
> > systems, you will most likely see differences in the solving process.
> >
> > The reason is that many decisions in a mathematical programming solver
> > are based on the results of floating point arithmetic calculations. Since
> > there are small differences across machines and compilers on how to deal
> > with round-off in floating point calculations, the decisions are affected
> > by machine type, compiler, and also compiler options. In particular for
> > MIP, a small difference in some decision can lead to a very large
> > difference in solving behavior.
> >
> >
> > Tobias
> >
> >
> >
> >
> > _________________________________________________________________________
> >__ _________ ¡Obtén la mejor experiencia en la web!
> > Descarga gratis el nuevo Internet Explorer 8.
> > http://downloads.yahoo.com/ieak8/?l=e1


-------------- next part --------------
A non-text attachment was scrubbed...
Name: eq.set
Type: text/x-objcsrc
Size: 12160 bytes
Desc: not available
Url : http://listserv.zib.de/mailman/private/scip/attachments/20091019/3d8869d5/eq.bin