[Coin-discuss] osiclpsolver optimal for infeasible problem?

[John J Forrest]

Rather embarrassing.

The problem started on this tiny example because it is also unbounded on 
x2 but it could have happened on other problems - the code somehow forgot 
that it was modifying an infeasibility weight and thought it had got in a 
loop!  Even then it should not said optimal.

I should have it fixed now.  Jan-Willem, I hope that fixes your problems 
and thanks for taking the time to create such a small example.

John



"Jan-Willem Goossens" <j.goossens at t75.nl> 
Sent by: coin-discuss-bounces at list.coin-or.org
03/13/2006 10:43 AM
Please respond to
Discussions about open source software for Operations Research 
<coin-discuss at list.coin-or.org>


To
coin-discuss at list.coin-or.org
cc

Subject
[Coin-discuss] osiclpsolver optimal for infeasible problem?






Hi all,

I tried to enter the following simple problem through the
OsiClpSolverInterface:

min  x1 - x2
s.t. x1 == -1

x1 >= 0, x2 >= 0

This problem is primal infeasible and also dual infeasible.
I enter it as follows


                 OsiClpSolverInterface *s = new OsiClpSolverInterface();

                 double inf = s->getInfinity();
                 CoinPackedVector empty;

                 s->addCol(empty, 0.0, inf, 1.0);
                 s->addCol(empty, 0.0, inf,  -1.0);

                 CoinPackedVector r0;
                 r0.insert(0, 1);
                 s->addRow(r0, -1.0, -1.0);

                 s->setObjSense(1);

                 s->initialSolve();

So the "x1 == -1" is entered as -1 <= x1 <= -1.

The output is as follows:

Coin0508I Presolve thinks problem is unbounded
Clp3003W Analysis indicates model infeasible or unbounded
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0006I 0  Obj 0 Primal inf 1 (1) Dual inf 1 (1)
Clp0032I Optimal objective 0 - 0 iterations time 0.052

The s->getColSolution() shows x1 = x2 = 0.0, and of all the "s->is...()"
functions, only s->isProvenOptimal() returns true.


Not unimportantly, I'm running this using Visual Studio .NET 2003, so
there might be something there.
I'm wondering if others get the same results?
Or am I missing something?

Regards,

Jan-Willem Goossens



_______________________________________________
Coin-discuss mailing list
Coin-discuss at list.coin-or.org
http://list.coin-or.org/mailman/listinfo/coin-discuss

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/coin-discuss/attachments/20060313/0bc2575a/attachment.html>