[Clp] ClpModel subproblem constructor accesses illegal elements in rhs->ray_

[Valentin Ziegler]

Hello,

I encountered an issue with Clp 1.11.0. The subproblem ctor

	ClpModel::ClpModel ( const ClpModel * rhs,
					int numberRows, const int *
whichRow,
					int numberColumns, const int *
whichColumn
					....

copies selected elements from rhs->ray_. Depending on the problem
status,
the superproblem's ray_ is interpreted as a column indexed or row
indexed vector:

	....
	if (problemStatus_==1)
		ray_ = whichDouble (rhs->ray_,numberRows,whichRow);
	else if (problemStatus_==2)
		ray_ = whichDouble
(rhs->ray_,numberColumns,whichColumn);
	....

However, it is possible that the superproblem's ray is still allocated
as a column
indexed array even though problemStatus==1. Consider following scenario:

- setupForRepeatedUse(2)
- create a dual infeasible LP with more rows than columns
- initialSolve
- modify row bounds so LP becomes primal infeasible
- resolve
- resolve again --> crash

Here, the first resolve creates a subproblem in
OsiClpSolverInterface::crunch().
Then, primal infeasibility is detected within that subproblem and the
subproblem's ray
is reallocated to hold a row indexed array. The superproblem's ray is
untouched and still
points to the column indexed array created by
ClpSimplexPrimal::primalRay(CoinIndexedVector * rowArray).

When the second resolve creates a new subproblem (problemStatus_ now
changed from 2 to 1),
the ClpModel ctor expects to find a row indexed vector in rhs->ray_ (see
above) and will
read over array bounds which occasionally leads to a crash.

With crunching disabled (special option 2048), the problem seems to
disappear.
Is there any chance to fix this (except for 2048) ? This would be a
great help to me.

Attached is a small code snipplet that triggers the problem described
above.

Many thanks
Valentin



--
Valentin Ziegler . vziegler at think-cell.com
Software Engineer
 
think-cell Software GmbH . Chausseestr. 8/E . 10115 Berlin, Germany 
http://www.think-cell.com . phone +49 30 666473-10 . toll-free (US) +1 800 891 8091
Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl . Amtsgericht Berlin-Charlottenburg, HRB 85229

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