<br><font size=2 face="sans-serif">Rather embarrassing.</font>
<br>
<br><font size=2 face="sans-serif">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.</font>
<br>
<br><font size=2 face="sans-serif">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.</font>
<br>
<br><font size=2 face="sans-serif">John</font>
<br>
<br>
<br>
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<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>"Jan-Willem Goossens"
<j.goossens@t75.nl></b> </font>
<br><font size=1 face="sans-serif">Sent by: coin-discuss-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">03/13/2006 10:43 AM</font>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
Discussions about open source software for Operations Research
<coin-discuss@list.coin-or.org></font></div></table>
<br>
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<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">coin-discuss@list.coin-or.org</font>
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<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td>
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<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">[Coin-discuss] osiclpsolver optimal
for infeasible problem?</font></table>
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<br>
<br>
<br><tt><font size=2>Hi all,<br>
<br>
I tried to enter the following simple problem through the<br>
OsiClpSolverInterface:<br>
<br>
min x1 - x2<br>
s.t. x1 == -1<br>
<br>
x1 >= 0, x2 >= 0<br>
<br>
This problem is primal infeasible and also dual infeasible.<br>
I enter it as follows<br>
<br>
<br>
OsiClpSolverInterface *s = new OsiClpSolverInterface();<br>
<br>
double inf = s->getInfinity();<br>
CoinPackedVector empty;<br>
<br>
s->addCol(empty, 0.0, inf, 1.0);<br>
s->addCol(empty, 0.0, inf, -1.0);<br>
<br>
CoinPackedVector r0;<br>
r0.insert(0, 1);<br>
s->addRow(r0, -1.0, -1.0);<br>
<br>
s->setObjSense(1);<br>
<br>
s->initialSolve();<br>
<br>
So the "x1 == -1" is entered as -1 <= x1 <= -1.<br>
<br>
The output is as follows:<br>
<br>
Coin0508I Presolve thinks problem is unbounded<br>
Clp3003W Analysis indicates model infeasible or unbounded<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0006I 0 Obj 0 Primal inf 1 (1) Dual inf 1 (1)<br>
Clp0032I Optimal objective 0 - 0 iterations time 0.052<br>
<br>
The s->getColSolution() shows x1 = x2 = 0.0, and of all the "s->is...()"<br>
functions, only s->isProvenOptimal() returns true.<br>
<br>
<br>
Not unimportantly, I'm running this using Visual Studio .NET 2003, so<br>
there might be something there.<br>
I'm wondering if others get the same results?<br>
Or am I missing something?<br>
<br>
Regards,<br>
<br>
Jan-Willem Goossens<br>
<br>
<br>
<br>
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<br>