[Osi] OsiCpx writeLp not working

[Matthew Galati]

It looks like the problem is related to the actual OsiCpx implementation.

Notice, if obj_ is non null, it does not get the new objective vector. 
That means, if a column is added, it does not get the new information. 
This is obviously not good. Ticket #62 added.

//------------------------------------------------------------------
const double * OsiCpxSolverInterface::getObjCoefficients() const
{
  debugMessage("OsiCpxSolverInterface::getObjCoefficients()\n");

  if ( obj_==NULL )
    {
      int ncols = CPXgetnumcols( env_, getMutableLpPtr() );
      if( ncols > 0 )
        {
          obj_ = new double[ncols];
          int err = CPXgetobj( env_, getMutableLpPtr(), obj_, 0, ncols-1 );
          checkCPXerror( err, "CPXgetobj", "getObjCoefficients" );
        }
    }
  return obj_;
}



> There seems to be a bigger problem at hand here.
>
> I start out with 5 columns in an OsiCpx object.
>
> If I use the base class Osi::getObjValue( ) after adding a column, I 
> get the correct number of columns, but junk back from 
> getObjCoefficients( ) and getColSolution( )
>
> MVG inside OsiSolverInterface nc = 6
> OsiCpxSolverInterface::getObjCoefficients()
> OsiCpxSolverInterface::getColSolution()
> OsiCpxSolverInterface::getDblParam(4)
> objOffset = 0
> MVG getObjValue i:0, retVal: -0, objCo: -15 colSol: 0
> MVG getObjValue i:1, retVal: -2.44186, objCo: -15 colSol: 0.162791
> MVG getObjValue i:2, retVal: -10.1163, objCo: -15 colSol: 0.511628
> MVG getObjValue i:3, retVal: -12.5581, objCo: -15 colSol: 0.162791
> MVG getObjValue i:4, retVal: -12.5581, objCo: -15 colSol: 0
> MVG getObjValue i:5, retVal: -12.5581, objCo: 1.56391e-311 colSol: 
> 7.20064e-313
> OsiCpxSolverInterface::getNumCols()
> MVG inside OsiSolverInterface nc = 6
>
>
>> If I addCols to my OsiCpx object -- it correctly keeps the 
>> information in memory, however when I call writeLp it calls the 
>> native Osi writer and does not seem to have my new columns - it only 
>> has the original problem. I assume this once again has something to 
>> do with cached information.
>>
>> One quick fix suggestion -- use Cpx's native LP writer just like we 
>> do for MPS. This is suggested in ticket 61.
>>
>> void OsiCpxSolverInterface::writeLp(const char *filename,
>>                                     const char *extension,
>>                                     double epsilon,
>>                                     int numberAcross,
>>                                     int decimals,
>>                                     double objSense,
>>                                     bool useRowNames) const
>> {
>>   debugMessage("OsiCpxSolverInterface::writeLp(%s, %s, %g)\n", 
>> filename, extens\
>> ion, objSense);
>>
>>   // *FIXME* : this will not output ctype information to the MPS file
>>   char filetype[4] = "LP";
>>   std::string f(filename);
>>   std::string e(extension);
>>   std::string fullname = f + "." + e;
>>   int err = CPXwriteprob( env_, getMutableLpPtr(), const_cast<char*>( 
>> fullname.\
>> c_str() ), filetype );
>>   checkCPXerror( err, "CPXwriteprob", "writeLp" );
>> }
>>
>>
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>>   
>