[Cbc-tickets] [COIN-OR Branch-and-Cut MIP Solver] #149: CBC reports incorrect optimal objective value

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

#149: CBC reports incorrect optimal objective value
-------------------+-----------------
Reporter:  vitaut  |      Owner:  tkr
    Type:  defect  |     Status:  new
Priority:  major   |  Component:  Cbc
 Version:  2.8.8   |   Keywords:
-------------------+-----------------
 CBC reports an incorrect optimal objective value when solving a trivial
 problem available in .nl format here:
 https://drive.google.com/file/d/0B8fdrkFjzN7mV2ZIODc5cnBIMm8/edit?usp=sharing

 Running

   cbc test.nl -AMPL

 produces a file test.sol containing the line:

   CBC 2.8.8 optimal, objective 4e+01

 Apart from strange formatting (the optimal value it tries to report is
 actually 45), the value is incorrect as can be checked with any other
 solver, e.g.

   cplex test.nl
   CPLEX 12.6.0.0: optimal solution; objective 15005
   4 dual simplex iterations (3 in phase I)

 One obvious issue is that the constant offset is not taken into account
 here: https://projects.coin-
 or.org/Cbc/browser/trunk/Cbc/src/CbcSolver.cpp?rev=1780#L2802

 However, even when taking the offset into account, one can still see that
 the value returned from CoinModel::getObjValue is wrong.

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Ticket URL: <https://projects.coin-or.org/Cbc/ticket/149>
COIN-OR Branch-and-Cut MIP Solver <http://projects.coin-or.org/Cbc>
An LP-based branch-and-cut MIP solver.