<br><font size=2 face="sans-serif">Francois,</font>
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<br><font size=2 face="sans-serif">The description of basisIsAvailable
does not say anything about an optimal basis. I thought it was more
so you can distinguish Volume algorithm.</font>
<br>
<br><font size=2 face="sans-serif">I can add optimalBasisIsAvailable if
you want but can the OsiCpx maintainer tell me what they think basisIsAvailable
means?</font>
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<br><font size=2 face="sans-serif">John</font>
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<br>
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<td width=40%><font size=1 face="sans-serif"><b>Francois Margot <fmargot@andrew.cmu.edu></b>
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<br><font size=1 face="sans-serif">Sent by: coin-lpsolver-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">11/08/2005 03:25 PM</font>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td valign=top><font size=1 face="sans-serif">coin-lpsolver@list.coin-or.org</font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">[Coin-lpsolver] basisIsAvailable()</font></table>
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<br><font size=2><tt><br>
The function OsiClpSolverInterface::basisIsAvailable() always returns<br>
true. This is a little bit dangerous. If modifications are made to the<br>
solver after the last optimization (change of bound on variables, in<br>
particular), the available basis might be (primal or dual, or both) <br>
infeasible.<br>
<br>
Then, calling cut generators such as Gomory and Reduce-and-Split might<br>
result in invalid cuts. The only way (as far as I can tell) to prevent
this<br>
is to rely on basisIsAvailable() to stop the cut generator if the current<br>
basis is not optimal anymore.<br>
<br>
Cplex is tracking the status of the basis accurately, but Clp does not.<br>
Is it possible to fix that?<br>
<br>
Thanks<br>
<br>
Francois<br>
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