[Coin-lpsolver] A bug. Re: Coin-lpsolver Digest, Vol 34, Issue 9

[John J Forrest]

Gleb,

You have not given enough information to track down your bug.  The matrix 
you point to has 418 rows and 563 columns (and is infeasible) so I don't 
see how columns and cuts can alternate.  Adding column C0000050 is fine, 
adding row R0000050 (with first 51 columns) is infeasible as there are no 
entries in row.

As to your other reported bug.  I can reproduce in 1.4 but not in 1.5.

I suggest you upgrade to 1.5 and see if this bug also goes away.

John Forrest



Gleb Belov <gleb.belov at tu-dresden.de> 
Sent by: coin-lpsolver-bounces at list.coin-or.org
09/20/2007 10:55 AM

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[Coin-lpsolver] A bug. Re: Coin-lpsolver Digest, Vol 34, Issue 9






Hello,

I use CLP 1.4.0 in a cut&price algorithm, i.e., column generation with 
cuts. In the following mps: 
http://www.math.tu-dresden.de/~belov/AFFconstr.mps, I started with a 
50x50 diagonal matrix and added columns and cuts interchangedly. After 
adding a column, I always executed primal. After adding a cut, I 
executed dual, then primal and tried to find new columns. Betwenn the 
two last constraints no columns were generated. The dual & primal 
methods were as well executed after adding the last cut. Now, when I 
check the solution, for the last constraint the sum on the left-hand 
side is -43.5 while it should be -44. Moreover, a variable with index 
980 is in the basis. It is obviously an internal slack for that row. 
But: its value is 0 in the Release compilation and 2e+218 in the Debug 
compilation!

Moreover, the function ClpModel::getRowUpper/Lower returns an array of 
zeros and ClpModel::matrix()->getCoef(i,j) always returns zero...

Best regards,
Gleb

-- 
Mit freundlichen Gruessen

G. Belov
----------------------------------------------------------------------
Dr. Gleb Belov                                Gleb.Belov at tu-dresden.de
Wiss. Assistent                   http://www.math.tu-dresden.de/~belov
Technische Universitaet Dresden                 Tel: +49 351 463 34186
Institut fuer Numerische Mathematik             Fax: +49 351 463 34268
Mommsenstr. 13                            Tel. priv.:+49 351 3743754
01062 Dresden

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