[Cbc] preprocessing problem

[John J Forrest]

Tuomo,

I can reproduce the error using cbc-stable/2.0 but the bug appears to have
been fixed in trunk.

I am hopeful that a new stable version will be out in a few days which will
have the current trunk fixes.

John Forrest


                                                                                                                          
  From:       Tuomo Takkula <tuomo.takkula at inform-ac.com>                                                                 
                                                                                                                          
  To:         cbc at list.coin-or.org                                                                                        
                                                                                                                          
  Date:       04/17/2008 10:09 AM                                                                                         
                                                                                                                          
  Subject:    [Cbc] preprocessing problem                                                                                 
                                                                                                                          





Hi,

on a mps file vanilla cbc reports

   Cgl0000I Cut generators found to be infeasible!
   Pre-processing says infeasible or unbounded

If I switch off preprocessing (preprocess off in cbc shell), then the
problems solves just fine. Is there a bug in preprocessing rendering a
feasible problem into an infeasible? Is there a simple way to get more
output from preprocessing (log and slog do not help).

The preprocess options I tried are the following:

off             solves
on              infeasible
equal           infeasible
sos             infeasible
trysos          infeasible
equalall        infeasible
strategy        solves after some complaints:
                 Cgl0000I Cut generators found to be infeasible!
                 Cbc0006I The LP relaxation is infeasible or too expensive
aggregate       infeasible


The mps file is available from me on request - write to
tuomo.takkula at inform-ac.com.


Best regards
Tuomo Takkula



--
__
Dr. Tuomo Takkula
Geschäftsbereich Systeme Logistik
INFORM GmbH,     Pascalstraße 23,    52076 Aachen
Telefon: +49-2408-14589-17, Fax: +49-2408-9456-45
tuomo.takkula at inform-ac.com,    www.inform-ac.com
Registered AmtsG Aachen HRB1144 Gfhr. Adrian Weiler
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