<br><font size=2 face="sans-serif">Francois,</font>
<br>
<br><font size=2 face="sans-serif">The performance hit is due to Clp using
CoinPackedMatrix. I had been informed about it being slow with addRow
and had written CoinBuild. I will extend that to do addColumn and
create a sample driver similar to addRows.cpp. I will give more details
when I finish it.</font>
<br>
<br><font size=2 face="sans-serif">John Forrest</font>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>François Galea <Francois.Galea@prism.uvsq.fr></b>
</font>
<br><font size=1 face="sans-serif">Sent by: coin-lpsolver-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">02/04/2005 03:15 AM</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>
<tr>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
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<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">[Coin-lpsolver] Problem creation
performance</font></table>
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<br>
<br>
<br><font size=2><tt>Hi !<br>
<br>
I have a question concerning the Clp library API.<br>
<br>
I need to generate different LPs (my previous question about QPs has no
<br>
relation with this problem), whose size is about 2500 rows, 2500 columns
<br>
and 250000 non-zeros. The model is such that it's easier for me to <br>
create an empty problem object using the ClpSimplex() constructor :<br>
<br>
ClpSimplex * simplex = new ClpSimplex();<br>
<br>
then I populate it column-wise, by first performing a series of calls <br>
like this:<br>
<br>
simplex->addRows( rcnt, lb, ub, rowstarts, NULL, NULL );<br>
<br>
then I add the columns by a series of this kind of calls :<br>
<br>
simplex->addColumns( 1, &lb, &ub, &objcoef, colstarts, ind,
val );<br>
<br>
This leads to a major problem, that the creation of the problem is much
<br>
slower than its resolution. Maybe Clp is more performant when creating
<br>
simplex objects row-wise than column-wise, but I really need to create
<br>
my problem objects this way.<br>
<br>
Most of the examples I found in the Clp documentation create ClpSimplex
<br>
objects by reading MPS files, and the only one I found that creates an
<br>
object from scratch provides the whole simplex matrix at once, which is
<br>
okay when you can easily find the size of the problem before creating <br>
the object, but it not okay for me.<br>
<br>
Could I get a link to a more complete documentation than the one I found
<br>
in the Clp website, which only mentions the addRows and addColumns <br>
methods once ? Or can anybody tell me why I get such a low model <br>
creation speed, and how to make things faster ?<br>
<br>
Thanks for the help,<br>
<br>
François Galea<br>
<br>
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</tt></font>
<br>