<br><font size=2 face="sans-serif">l30 seems to work for me - 40 seconds
and 8700 iterations. It has many free variables and used to give
problems.</font>
<br>
<br><font size=2 face="sans-serif">What driver are you using and what compiler?
Does it fail with -g as then I should be able to track it down?</font>
<br>
<br><font size=2 face="sans-serif">John Forrest</font>
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<br>
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<td width=40%><font size=1 face="sans-serif"><b>Kish Shen <ks15@icparc.ic.ac.uk></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">08/19/2005 11:12 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] (no subject)</font></table>
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<br><font size=2><tt>Hi,<br>
<br>
In one of the test I am running, I ran into a possible problem with Clp:
<br>
<br>
the solver seems to be taking a very long time to solve the linear problem<br>
l30, which is one of the problems used in Mittelmann's benchmarks. In his<br>
webpage for the latest results (ftp://plato.asu.edu/pub/lpfree.html), he<br>
lists the solving time for this problem as 80s, although it is not stated<br>
what method was used to solve this problem.<br>
<br>
I have setup Clp to use the dual simplex method via the OSI calls:<br>
<br>
lpd->lp->setHintParam(OsiDoDualInInitial, true, OsiHintDo,
NULL);<br>
lpd->lp->setHintParam(OsiDoDualInResolve, true, OsiHintDo,
NULL);<br>
<br>
and so far, Clp have spent more than 80,000 seconds to try and solve this<br>
problem, and as far as I can tell, it is still in phase 1, because the<br>
objective value is not moving uniformly in one direction.<br>
<br>
Both CPLEX and Xpress are able to solve this problem with dual simplex
in<br>
under 70 seconds, and SoPLEX in under 100 seconds. So far, for all other<br>
problems, I have not seen such a big difference between the solving times<br>
for Clp and the other solvers. Is this possibly a bug, or is it simply
`bad<br>
luck' because the pivot selections etc. happens to be very bad for this<br>
problem for Clp?<br>
<br>
Clp is able to solve this problem using primal Simplex in 208 seconds,
so<br>
perhaps the Mittlemann result is using primal simplex (his timings for
the<br>
other results are about 2-3 times faster than what I get on our machines<br>
here), even though I thought the normal default for Clp is to use dual
simplex.<br>
<br>
Cheers,<br>
<br>
Kish Shen<br>
Imperial College London<br>
U.K.<br>
<br>
<br>
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