[Coin-discuss] 2 error + 1 ,may be, recommended correction

[John J Forrest]

Sandor,

I can not duplicate the error.  When you say buffer overflow do you mean a 
segmentation fault or a memory checker report of an error?

I downloaded a clean copy of clp and added lots of asserts and was running 
electricfence but got no errors.

Using -g 
RedHat 9.0 Pentium 4
gcc 3.2.2

The sizes should be number of rows for dual and number of rows+columns for 
primal.  An overflow would be an error.  The idea is that on large 
problems the infeasibilities (primal or dual) change slowly so that it is 
worth keeping a list and updating it (especially as we need square of 
infeasibility for steepest edge algorithms).  If a variable was infeasible 
and goes feasible then the infeasibility value is not set to zero (as then 
we might add it back again and then we could get overflow) but to 
1.0e-100.

Any further information would be helpful - maybe just to me and not posted 
for discussion.

John Forrest



sandor szedmak <ss03v at ecs.soton.ac.uk> 
Sent by: coin-discuss-admin at www-124.southbury.usf.ibm.com
03/11/2004 06:15 AM
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Subject
[Coin-discuss] 2 error + 1 ,may be, recommended correction






Hi,

I just started to use Clp from COIN.
I found two buffer overflow errors:

---------------------------------------------------
1.
In the file:
    ClpDualRowSteepest.cpp 
the buffer infeasible_ goes beyond its capacity.

The error can be produced by
    clp -unitTest
using the file
    finnis.mps

A possible correction can be
      infeasible_ = new CoinIndexedVector();
      infeasible_->reserve(max(numberRows,numberColumns));
or
      infeasible_ = new CoinIndexedVector();
      infeasible_->reserve(numberRows+numberColumns);
in the function
    ClpDualRowSteepest::saveWeights(ClpSimplex * model,int mode)

The original version is
      infeasible_ = new CoinIndexedVector();
      infeasible_->reserve(numberRows);
--------------------------------------------------
2.
In the file
    ClpPrimalColumnSteepest.cpp
the buffer infeasible_ does the same that is in ClpDualRowSteepest.cpp.

The error can be produced by
    clp -unitTest
using the file
    brandy.mps

 Here the correction that was suggested previously has been made already.
( to increase the size of infeasible_ by use of 
infeasible_->reserve(numberRows+numberColumns); )

It happens in the function

ClpPrimalColumnSteepest::pivotColumn(CoinIndexedVector * updates,
                    CoinIndexedVector * spareRow1,
                    CoinIndexedVector * spareRow2,
                    CoinIndexedVector * spareColumn1,
                    CoinIndexedVector * spareColumn2)

To change "quickAdd" to "add" does not help on this problem.
Unfortunately I have not found a appropriate correction to this error yet.

-------------------------------------------------
My programming environment:

Suse Linux 8.2(Intel Pentium),
GNU C++  3.3-23
Coin + Clp was downloaded by cvs on 8/03/2004
------------------------------------------------

Best regards

Sandor Szedmak
Electronics and Computer Science
University of Southampton
United Kingdom


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