[Cbc-tickets] [COIN-OR Branch-and-Cut MIP Solver] #56: CBC produce wrong solution and inconsistent solution between CBC 2.2 and CBC trunk

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

#56: CBC produce wrong solution and inconsistent solution between CBC 2.2 and
CBC trunk
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  Reporter:  cents       |       Owner:  somebody                             
      Type:  defect      |      Status:  closed                               
  Priority:  major       |   Milestone:                                       
 Component:  component1  |     Version:  2.0                                  
Resolution:  fixed       |    Keywords:  wrong solution inconsistent objective
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Changes (by forrest):

  * status:  new => closed
  * resolution:  => fixed

Comment:

 This seems to be a tolerance issue.  There are some small coefficients in
 matrix so preprocessed model may behave differently from processed model.
 I think trunk is correct in both cases as I put in stricter tests - you
 may see some messages in trunk output rejecting solutions.

 There are various possibilities -
 1) code refuses to cheat by setting integer variables to small values -
 answer 0.0
 2) code thinks preprocessed model has solution of -19.... but when
 original model is solved with integer variables fixed to those values
 objective is 0.0

 I have modified code to print messages to try and help clarify situation.

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Ticket URL: <https://projects.coin-or.org/Cbc/ticket/56#comment:1>
COIN-OR Branch-and-Cut MIP Solver <http://projects.coin-or.org/Cbc>
An LP-based branch-and-cut MIP solver.