[Osi] [Coin-discuss] OsiCpx writeMps does not print integer info

[Ted Ralphs]

For completeness, here is a long thread on the topic (also initiated by Matt :))

http://list.coin-or.org/pipermail/osi/2008-June/000138.html

Ted

On Wed, Apr 28, 2010 at 9:35 AM, Ted Ralphs <ted at lehigh.edu> wrote:
> I'm switching this thread over to the OSI list.
>
> On Wed, Apr 28, 2010 at 8:43 AM, Stefan Vigerske
> <stefan at math.hu-berlin.de> wrote:
>
>>> When using writeMps with OsiCpx, the integer information is lost. Using writeLp works, but not writeMps. How do I fix this?
>>
>> You remember, whether you solve the LP relaxation or the MIP before
>> calling writeMps?
>> Does it work better if you add "switchToMIP();" in the beginning of
>> OsiCpx::writeMps?
>>
>> writeMps calls the CPLEX MPS writing function, while writeLp uses an Osi
>> function. That may make a difference.
>
> Yes, OsiCpx has some strangeness coming from the fact that switching
> the problem type from LP to MIP erases cached solution information.
> I'm pretty sure that the problem is that CPLEX is storing the problem
> as an LP instead of a MIP most of the time to avoid this difficulty.
> There have been several discussions of this on the list in the past.
> It should be easy to see what's going on by looking at the source.
> Another solution would be to switch to using the MPS writer in
> CoinUtils instead.
>
> Cheers,
>
> Ted
> --
> Dr. Ted Ralphs
> Associate Professor, Lehigh University
> (610) 628-1280
> ted 'at' lehigh 'dot' edu
> coral.ie.lehigh.edu/~ted
>



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