[Osi] issue in OsiCbc - corrupting bounds

Ted Ralphs ted at lehigh.edu
Mon Aug 9 16:04:41 EDT 2010


Is there any debate over the fact that API functions in OSI should
have consistent behavior over solvers whenever possible? Yes, there
have been cases where that's difficult/impossible to enforce for some
reason related to the implementation of the underlying solver, but in
my view, solver independence is the most important principle and
should be enforced in all but the most extreme cases. Otherwise, the
usability of Osi is reduced significantly. Of course, there is the
problem of different solvers having different sets of parameters, but
that is a separate issue really. This particular case seems clear cut.
The way OsiCbc behaves is inconsistent and I think we should just fix
it.

As an aside, the problem at the moment with fixing bugs in Osi is that
the trunk of Osi is incompatible with anything but the trunk of Cbc
(due to the changes we are implementing in the build tools and the
reorganization of source code that just occurred in the Osi trunk).
The trunk of Cbc is in turn incompatible with Dip, among others,
because those haven't been converted yet. So for a bug fix to be
useful right now, we would have to propogate it out to the current
stable and make a new release.

Cheers,

Ted

On Mon, Aug 9, 2010 at 1:11 PM, Lou Hafer <lou at cs.sfu.ca> wrote:
> Folks,
>
>> Anyway, to achieve solver independence it should be OsiCbc's job to
>> hide [ modification of the problem representation ] from the user:
>
>        Presumably this could be done with the saveReferenceSolver /
> resetToReferenceSolver calls, inside OsiCbc. Matt, how motivated are you? Want
> to give this a try and see if it works for you? It might be a while before it
> rises to the top of someone elses' to-do list.
>
>        Anyone out there howling that this change will break their code?
>
>                                                        Lou
>
> _______________________________________________
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> Osi at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/osi
>



-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted





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