[Cbc-tickets] [COIN-OR Branch-and-Cut MIP Solver] #58: Cbc 2.2 reports model integer-infeasible, actually feasible

[COIN-OR Branch-and-Cut MIP Solver]

#58: Cbc 2.2 reports model integer-infeasible, actually feasible
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 Reporter:  nowozin     |       Owner:  somebody
     Type:  defect      |      Status:  new     
 Priority:  major       |   Milestone:          
Component:  component1  |     Version:          
 Keywords:              |  
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 Cbc 2.2 reports the attached model (submitted to the lp-solve mailing list
 for examination) as integer feasible:

 {{{
 Coin Cbc and Clp Solver version 2.20.00, build Sep 20 2008
 command line - /opt/coin-cbc-2.2.0/bin/cbc out.mps
 At line 8 NAME
 At line 9 ROWS
 At line 2700 COLUMNS
 At line 137775 RHS
 At line 138113 BOUNDS
 At line 141138 ENDATA
 Problem no_name has 2689 rows, 4032 columns and 268128 elements
 Coin0008I no_name read with 0 errors
 Continuous objective value is 145980 - 0.15 seconds
 Perturbing problem by 0.001 % of 478.647 - largest nonzero change
 0.00146329 (% 0.000305713) - largest zero change 0.000244159
 0  Obj 145980 Primal inf 3349.78 (576)
 Primal infeasible - objective value 153640
 Cgl0000I Cut generators found to be infeasible!
 Pre-processing says infeasible or unbounded
 Total time 0.73
 }}}

 I personally verified Cplex 9.1 also reports the model infeasible, whereas
 people report later versions of Cplex, Xpress MP and SCIP producing
 integer-feasible solutions.

-- 
Ticket URL: <https://projects.coin-or.org/Cbc/ticket/58>
COIN-OR Branch-and-Cut MIP Solver <http://projects.coin-or.org/Cbc>
An LP-based branch-and-cut MIP solver.