[Osi] OsiClp gives wrong iteration count?

[John J Forrest]

Jan-Willem,

It is a bug which crept in.  I was trying to get a more accurate count in
the case when OsiClp does two solves (e.g. dual followed by primal) and
missed out a line.  Can occur in initialSolve from an all slack basis.

John


                                                                                              
  From:       Goossens Jan-Willem <Jan-Willem.Goossens at nc3a.nato.int>                         
                                                                                              
  To:         osi <osi at list.coin-or.org>                                                      
                                                                                              
  Cc:         "Goossens Jan-Willem \[Internet\]" <Jan-Willem.Goossens at nc3a.nato.int>          
                                                                                              
  Date:       07/30/2009 09:45 AM                                                             
                                                                                              
  Subject:    [Osi] OsiClp gives wrong iteration count?                                       
                                                                                              
  Sent by:    osi-bounces at list.coin-or.org                                                    
                                                                                              





Hi,

Either it's me, or the iteration count reported through
OsiClpSolverInterface is wrong.

The following code solves a small problem:

        OsiClpSolverInterface model;

        int start[] = { 0, 1, 2};
        int index[] = { 0, 0};
        double values[] = {1.0, 2.0};
        double collb[] = {0.0, 0.0};
        double colub[] = {10.0, 10.0};
        double obj[] = { 1.0, 1.0};
        double rowlb[] = { 0.0};
        double rowub[]= { 3.9};

        // obj: Max x0 + x1
        //  st. x0 + 2 x1 <= 3.9
        //              0 <= x0 <= 10 and integer
        //              0 <= x1 <= 10
        model.loadProblem(2, 1, start, index, values, collb, colub, obj,
rowlb, rowub);
        model.setObjSense(-1.0);
        model.initialSolve();

        std::cout << "algorithm:" << model.lastAlgorithm() << std::endl;
        std::cout << "iteration count:" << model.getIterationCount() <<
std::endl;


The output is

Coin0506I Presolve 1 (0) rows, 2 (0) columns and 2 (0) elements
Clp0006I 0  Obj -0 Dual inf 2 (2)
Clp0006I 1  Obj 3.9
Clp0000I Optimal - objective value 3.9
Clp0032I Optimal objective 3.9 - 1 iterations time 0.012
algorithm:2
iteration count:0

So, Clp says "1 iterations", but the OsiClpSolverInterface says 0.

Is this a bug or a feature?

I'm working with the source as they come with Cbc-2.3.0..
Thanks in advance,

Jan-Willem Goossens


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