<font size=2 face="sans-serif">I'm obviously interested in the -extraVariables
feature (though I'd like some guidance on how to pick the value). Is this
available now from svn, or am I waiting for a version to be "published"?</font>
<br>
<br><font size=2 face="sans-serif">Allan Wechsler</font>
<br>
<br>
<br>
<table width=100%>
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<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">John Forrest <john.forrest@fastercoin.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td>
<tr>
<td valign=top><font size=1 color=#5f5f5f face="sans-serif">Cc:</font>
<td><font size=1 face="sans-serif">cbc@list.coin-or.org</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">03/19/2013 10:20 AM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">[Cbc] New trunks and note on infeasibility
ray.</font></table>
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<hr noshade>
<br>
<br>
<br><font size=3>I have produced some new trunk versions. I found
I had been updating the wrong versions so Cbc/trunk will be updated again
in a day or two.<br>
<br>
Cgl has some fixes plus two cut generators donated by Giacomo Nannicini.
One is an alternative reduce and split generator (G. Cornuejols and
G. Nannicini. Practical strategies for generating rank-1 split cuts in
mixed-integer linear programming. <i>Mathematical Programming Computation</i>,
3(4):281-318, 2011) while the other is a robust Gomory generator (G. Cornuejols,
F. Margot and G. Nannicini. On the safety of Gomory cut generators. <i>Mathematical
Programming Computation</i>) - see </font>
<br><a href="http://faculty.sutd.edu.sg/%7Enannicini/index.php?page=publications"><tt><font size=3 color=blue><u>http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications</u></font></tt></a><tt><font size=3><br>
<br>
</font></tt><font size=3 face="sans-serif">As reduce and split cuts can
be slow, the full benefit will not be felt before my next Cbc/trunk when
there will be a parameter for specifying number of rounds to do for expensive
cuts.<br>
<br>
Coinutils/trunk has a few changes to presolve for special variables and
badly scaled problems.<br>
<br>
Cbc will change again, but one feature of interest to Allan Wechsler is
-extraVariables 20 (or some such) which switches on a trivial re-formulation
to group variables with same cost together.<br>
<br>
The feature which may affect people is for returning a primal infeasibility
ray. The previous code passed the unit test, but on close examination
that was when Clp had switched to Primal. Hopefully I have now got
the signs right for Dual as well. So if you use infeasibility rays
- try trunk and if fails reverse signs! At least it should be more
consistent - and should be same as other Lp codes.<br>
<br>
John Forrest<br>
</font><tt><font size=3> <br>
<br>
<br>
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