[Clp-tickets] [COIN-OR Linear Programming Solver] #3: fix failed assertion in CoinPackedMatrix::removeGaps

[COIN-OR Linear Programming Solver]

#3: fix failed assertion in CoinPackedMatrix::removeGaps
------------------------+---------------------------------------------------
 Reporter:  dmg         |       Owner:  somebody
     Type:  defect      |      Status:  new     
 Priority:  major       |   Milestone:          
Component:  component1  |     Version:          
 Keywords:              |  
------------------------+---------------------------------------------------
 We have an example (in a Sandia application that calls the
 COIN MIP solver) in which line 2368 of ClpPackedMatrix::allElementsInRange
 invokes

         matrix_->compress(smallest);

 and soon thereafter we get a failed assertion at CoinPackedMatrix.cpp:604.
 Here's a partial traceback at the invocation of
 matrix_->compress(smallest:

 #0  ClpPackedMatrix::allElementsInRange (this=0x8d8dbb0, model=0xbff76c2c,
     smallest=9.9999999999999995e-21, largest=1e+20, check=15)
     at ClpPackedMatrix.cpp:2368
 #1  0x081ee330 in ClpPresolve::presolvedModel (this=0xbff766a0,
     si=@0xbff76c2c, feasibilityTolerance=1e-08, keepIntegers=false,
     numberPasses=5, dropNames=true, doRowObjective=false) at
 ClpPresolve.cpp:97
 #2  0x08260f59 in ClpSimplex::initialSolve (this=0xbff76c2c,
     options=@0xbff76f80) at ClpSolve.cpp:590
 #3  0x081ae2a7 in OsiClpSolverInterface::initialSolve (this=0x8d8d288)
     at OsiClpSolverInterface.cpp:274

 and here's a partial traceback at the failed assertion:

 #0  0x00edf402 in __kernel_vsyscall ()
 #1  0x00324f90 in raise () from /lib/libc.so.6
 #2  0x00326678 in abort () from /lib/libc.so.6
 #3  0x0031e269 in __assert_fail () from /lib/libc.so.6
 #4  0x08071a56 in CoinPackedMatrix::removeGaps (this=0x8d98c60)
     at CoinPackedMatrix.cpp:604
 #5  0x081f3fd2 in ClpPresolve::gutsOfPresolvedModel (this=0xbff766a0,
     originalModel=0xbff76c2c, feasibilityTolerance=1e-08,
 keepIntegers=false,
     numberPasses=5, dropNames=true, doRowObjective=false)
     at ClpPresolve.cpp:1718
 #6  0x081ee36d in ClpPresolve::presolvedModel (this=0xbff766a0,
     si=@0xbff76c2c, feasibilityTolerance=1e-08, keepIntegers=false,
     numberPasses=5, dropNames=true, doRowObjective=false)
     at ClpPresolve.cpp:102
 #7  0x08260f59 in ClpSimplex::initialSolve (this=0xbff76c2c,
     options=@0xbff76f80) at ClpSolve.cpp:590
 #8  0x081ae2a7 in OsiClpSolverInterface::initialSolve (this=0x8d8d288)
     at OsiClpSolverInterface.cpp:274

 As a work-around (which may not accord with your design philosophy), I
 modified our copy of the COIN source as follows:  I added

         int really_compress(double threshold);

 to CoinPackedMatrix (in CoinUtils/src/CoinPackedMatrix.hpp),
 changed line 2368 ofClp/src/ClpPackedMatrix.cpp to

     matrix_->really_compress(smallest);

 and added the following implementation of really_compress to
 CoinUtils/src/CoinPackedMatrix.cpp:

 int
 CoinPackedMatrix::really_compress(double threshold)
 {
   CoinBigIndex i, j, k, k0, m, n, nelim;
   m = majorDim_;
   for (i = k = nelim = 0; i < m; i++) {
     j = start_[i];
     start_[i] = k0 = k;
     for (n = j + length_[i]; j < n; j++) {
       if (fabs(element_[j])>=threshold) {
         element_[k]=element_[j];
         index_[k++]=index_[j];
       } else {
         ++nelim;
       }
     }
     length_[i] = k - k0;
   }
   start_[m] = k;
   size_ -= nelim;
   return nelim;
 }

-- 
Ticket URL: <https://projects.coin-or.org/Clp/ticket/3>
COIN-OR Linear Programming Solver <http://projects.coin-or.org/Clp>
A linear programming solver.