[Symphony-tickets] [SYMPHONY] #61: Deleting Rows and Columns with OsiSymSolverInterface fails

[SYMPHONY]

#61: Deleting Rows and Columns with OsiSymSolverInterface fails
-----------------------------------------+----------------------------------
 Reporter:  lutz.goehring                |       Owner:  tkr  
     Type:  defect                       |      Status:  new  
 Priority:  major                        |   Milestone:  5.2  
Component:  Not Sure                     |     Version:  5.1.2
 Keywords:  delete rows, delete columns  |  
-----------------------------------------+----------------------------------
 I am having a problem of size  553 x 2320 stored in Class of type
 AgentProblem and consisting of a sparse matrix which I attached as MPS.
 To reduce the problem size I  delete the zero rows and columns by doing
 something like:

 ...
 AgentProblem* specificProblem;
 specificProblem->loadProblem(....),//load problem from somewhere

 specificProblem->findEmptyRowsAndCols();

 OsiSymSolverInterface::deleteRows( specificProblem-
 >getNumberOfRowsToDrop() , specificProblem->getRowsToDrop() );
 OsiSymSolverInterface::( specificProblem->getNumberOfColsToDrop() ,
 specificProblem->getColsToDrop() );

 to delete rows and cols which are zero.
 During runtime this results in the Error message:

 *** glibc detected *** double free or corruption (!prev): 0x08605f00 ***
 Aborted

 In parallel, I am also using OSL via the OsiSolverInterface:

 OsiOslSolverInterface::deleteRows( specificProblem-
 >getNumberOfRowsToDrop() , specificProblem->getRowsToDrop() );
 OsiOslSolverInterface::( specificProblem->getNumberOfColsToDrop() ,
 specificProblem->getColsToDrop() );

 This works fine and gives the correct result.

 While looking at the mps I realized that the zero rows and columns are
 thrown out anyway right away by SYMPHONY. So I conjecture that deleting
 zero rows and cols is superfluous?!

 The code for finding the empty Rows and cols is the following:

 void AgentProblem::findEmptyRowsAndCols(){
         numberofrowstodrop = 0;
         numberofcolstodrop = 0;
         //find rows to delete:
         for (int i = 0;  i < getNumRows(); i++) {
                 bool mark = true;
                 if ( fabs(getRightHandSide()[i]) > eps ) continue;
                 for (int j = 0; j < getNumCols(); j++)
                         if (fabs(getMatrixByCol()->getCoefficient(i,j)) >
 eps  ){
                                 mark = false;
                                 continue;
                         }
                 if (mark) rowsToDrop[numberofrowstodrop++] = i;
         }
         //find columns to delete:
         for (int j = 0;  j < getNumCols(); j++) {
                 bool mark = true;
                 if ( fabs(getObjCoefficients()[j]) > eps ) continue;
                 for (int i = 0; i < getNumRows(); i++)
                         if (fabs(getMatrixByCol()->getCoefficient(i,j)) >
 eps  ) {
                                 mark = false;
                                 continue;
                         }
                 if (mark) colsToDrop[numberofcolstodrop++] = j;
         }
 }

-- 
Ticket URL: <https://projects.coin-or.org/SYMPHONY/ticket/61>
SYMPHONY <http://projects.coin-or.org/SYMPHONY>
The SYMPHONY framework for parallel branch-and-cut algorithms.