[Cbc] "Integer infeasible..." issue?

[John Forrest]

James,

It is not a bug in Cbc, but an error (feature?) in Coin's lp format 
reader.  The reader does not like the last two constraints - if I replace

/p0_2 + p1_2 = x2//
//p0_3 + p1_3 = x3

by

////p0_2 + p1_2 - x2 = 0//
//p0_3 + p1_3 - x3//= 0

everything is fine

John Forrest
/

On 08/05/15 09:07, James Gunning wrote:
> Hello All,
>         This is probably a dumb question: why does this simple .lp file
>
> /Min//
> //obj: -10.9139 p1_3 +15.3211 x1 -3.30662 x3 //
> //s.t.//
> //x0 - p0_2 >= 0//
> //x2 - p0_2 >= 0//
> //p0_2 - x0 - x2 >= -1//
> //x0 - p0_3 >= 0//
> //x3 - p0_3 >= 0//
> //p0_3 - x0 - x3 >= -1//
> //x1 - p1_2 >= 0//
> //x2 - p1_2 >= 0//
> //p1_2 - x1 - x2 >= -1//
> //x1 - p1_3 >= 0//
> //x3 - p1_3 >= 0//
> //p1_3 - x1 - x3 >= -1//
> //x0 + x1 = 1//
> //x2 + x3 = 1//
> //p0_2 + p1_2 = x2//
> //p0_3 + p1_3 = x3//
> //Binaries//
> //x0 x1 x2 x3 p0_2 p0_3 p1_2 p1_3//
> //End/
>
>
>
> Give me "Integer infeasible..." under cbc?
>
> lp_solve gives me an integer solution
>
> p1_3                            0
> x1                              0
> x3                              1
> x0                              1
> p0_2                            0
> x2                              0
> p0_3                            1
> p1_2                            0
>
>
>
> I'm sure I've done something stupid, but it may be a subtle roundoff 
> thing?
> This is cbc 2.8.12.
>
> Best wishes all & kudos to John for keeping things going so well...
>        James.
>
>
>
>
>
> _______________________________________________
> Cbc mailing list
> Cbc at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/cbc

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20150508/7d08b57e/attachment.html>