[Cbc-tickets] [COIN-OR Branch-and-Cut MIP Solver] #69: CBC 2.2.2 returns sub-optimal solution

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

#69: CBC 2.2.2 returns sub-optimal solution
------------------------+---------------------------------------------------
 Reporter:  knark       |       Owner:  somebody
     Type:  defect      |      Status:  new     
 Priority:  major       |   Milestone:          
Component:  component1  |     Version:  2.0     
 Keywords:              |  
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 CBC 2.2.2 returns an objective value of -960 for the attached small MIP
 model while the optimal objective value is -1160. I used MS V8 on Windows.


 {{{
 Coin Cbc and Clp Solver version 2.20.00, build Feb 25 2009
 command line - cbcsolve cbc00001.mps -solve
 At line 1 NAME          BLANK
 At line 2 ROWS
 At line 5 COLUMNS
 At line 17 RHS
 At line 19 BOUNDS
 At line 31 ENDATA
 Problem BLANK has 1 rows, 11 columns and 11 elements
 Coin0008I BLANK read with 0 errors
 Continuous objective value is -1194.03 - 0.00 seconds
 Optimal - objective value -1194.03
 Cgl0004I processed model has 0 rows, 0 columns (0 integer) and 0 elements
 Cbc3007W No integer variables - nothing to do
 Cuts at root node changed objective from -960 to -1.79769e+308
 Probing was tried 0 times and created 0 cuts of which 0 were active after
 adding rounds of cuts (0.000 seconds)
 Gomory was tried 0 times and created 0 cuts of which 0 were active after
 adding rounds of cuts (0.000 seconds)
 Knapsack was tried 0 times and created 0 cuts of which 0 were active after
 adding rounds of cuts (0.000 seconds)
 Clique was tried 0 times and created 0 cuts of which 0 were active after
 adding rounds of cuts (0.000 seconds)
 MixedIntegerRounding2 was tried 0 times and created 0 cuts of which 0 were
 active after adding rounds of cuts (0.000 seconds)
 FlowCover was tried 0 times and created 0 cuts of which 0 were active
 after adding rounds of cuts (0.000 seconds)
 TwoMirCuts was tried 0 times and created 0 cuts of which 0 were active
 after adding rounds of cuts (0.000 seconds)
 Result - Finished objective -960 after 0 nodes and 0 iterations - took
 0.00 seconds (total time 0.00)
 Total time 0.00
 }}}

 The CBC version at COIN-OR returns the correct value of -1160:


 {{{
 Coin Cbc and Clp Solver version 1.01.00, build Aug 18 2006 command line -
 /home/neos/neos-bin/cbc cbc.mps
 At line 1 NAME          BLANK
 At line 2 ROWS
 At line 5 COLUMNS
 At line 17 RHS
 At line 19 BOUNDS
 At line 31 ENDATA
 Problem BLANK has 1 rows, 11 columns and 11 elements
 Model was imported from ./cbc.mps in 0 seconds
 Optimal - objective value -1194.03
 Cgl0004I processed model has 1 rows, 11 columns (11 integer) and 11
 elements processed model has 1 rows, 11 columns and 11 elements Optimal -
 objective value -1184 11 integer variables
   - solution found
 Cbc0012I Integer solution of -1160 found by heuristic after 0 iterations
 and 0 nodes (0.01 seconds)
 }}}

-- 
Ticket URL: <https://projects.coin-or.org/Cbc/ticket/69>
COIN-OR Branch-and-Cut MIP Solver <http://projects.coin-or.org/Cbc>
An LP-based branch-and-cut MIP solver.