[Coin-lpsolver] determining infeasibility in ClpInterior
John J Forrest
jjforre at us.ibm.com
Fri Nov 17 04:40:17 EST 2006
It is a known defect that the Clp barrier does not detect infeasibility or
unboundedness correctly. It is on my list of the 100 things most wanted
:-)
On getting solutions use dualRowSolution() and/or primalColumnSolution()
and check feasibility (either by hand or by checkSolution();
messages should be out by default on trunk and branches/devel
John Forrest
Kish Shen
<kish.shen at crossc
oreop.com> To
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[Coin-lpsolver] determining
infeasibility in ClpInterior
11/16/06 07:49 PM
Hi,
I have been testing out ClpInterior with some test cases, and for the
following simple problem:
objective: min(X)
subject to:
X + Y >= 3
X + Y <= 2
X - Y = 0
which is obviously infeasible, and when I solve the problem with Clp's
Simplex, this is indeed
what I get. However, when I solve the problem with ClpInterior, I get a
solution (with X and
Y = 1).
Looking at the code:
lpd->lp->interiormodel->setCholesky(cholesky);
lpd->lp->interiormodel->primalDual();
// Barrier done
if (lpd->lp->interiormodel->isProvenOptimal())
{
// Do crossover if optimal...
.....
}
where lpd->lp->interiormodel is a ClpInterior *, the isProvenOptimal()
method returns true.
I assume it should not?
--Kish Shen
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