<font size=2 face="sans-serif">The objective is a linear combination of
some set of variables. Of course I don't know what your objective
function is, but let's call it F.</font>
<br>
<br><font size=2 face="sans-serif">Since this is a minimization problem,
I propose adding one more constraint to the problem, F >= -1e6. If
unboundedness is the problem, the modified problem will solve with no trouble.</font>
<br>
<br><font size=2 face="sans-serif">In your first response, you mention
variable bounds. Do you have bounds on all your variables? If
you do, then my analysis is probably wrong and the difficulty is infeasibility
rather than unboundedness.</font>
<br>
<br><font size=2 face="sans-serif">It should not be necessary to know any
solver internals to figure out what's wrong.</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">Christos <chtsolak@gmail.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td><font size=1 face="sans-serif">acw@ascent.com</font>
<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" <cbc@list.coin-or.org>,
Allan Wechsler <acw@robson.ascent.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">08/10/2012 12:37 PM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">Re: [Cbc] Artificial variables</font></table>
<br>
<hr noshade>
<br>
<br>
<br><font size=3>I forgot to mention that it is a minimization problem
, so i do not know if there is any point in limiting objective.<br>
<br>
Sorry for the double mail.<br>
<br>
On 10/8/2012 19:24, </font><a href=mailto:acw@ascent.com><font size=3 color=blue><u>acw@ascent.com</u></font></a><font size=3>
wrote:</font>
<br><font size=2 face="sans-serif">No single constraint is responsible
for an infeasibility. Consider a system with one variable, and two
constraints, X >= 7 and X <= 4. This system is obviously infeasible,
but which of the two constraints is at fault?</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
In your case I suspect that the problem is unbounded rather than infeasible,
because you have so few constraints and so many variables. Unless
the problem has a very special structure, a problem with fewer constraints
than variables is likely to be unbounded.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
You can check this by adding a constraint that limits your objective to,
say, 1e6. If the problem now solves, then unboundedness is almost
certainly your difficulty.</font><font size=3> <br>
<br>
</font>
<table width=100%>
<tr valign=top>
<td width=22%><font size=1 color=#5f5f5f face="sans-serif">From:</font><font size=3>
</font>
<td width=77%><font size=1 face="sans-serif">Christos </font><a href=mailto:chtsolak@gmail.com><font size=1 color=blue face="sans-serif"><u><chtsolak@gmail.com></u></font></a><font size=3>
</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font><font size=3>
</font>
<td><a href="mailto:cbc@list.coin-or.org"><font size=1 color=blue face="sans-serif"><u>cbc@list.coin-or.org</u></font></a><font size=3>
</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font><font size=3>
</font>
<td><font size=1 face="sans-serif">08/10/2012 09:32 AM</font><font size=3>
</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font><font size=3>
</font>
<td><font size=1 face="sans-serif">[Cbc] Artificial variables</font></table>
<br><font size=3><br>
</font>
<hr noshade><font size=3><br>
<br>
</font><tt><font size=2><br>
Hi, i have a model with around 10000 variable and 1500 equations.<br>
<br>
But i get the messages on the photo when i run it:</font></tt><font size=3 color=blue><u><br>
</u></font><a href="http://imageshack.us/photo/my-images/39/dascd.png/"><tt><font size=2 color=blue><u>http://imageshack.us/photo/my-images/39/dascd.png/</u></font></tt></a><tt><font size=2><br>
<br>
Is there any way to use artificial variable or something else in order
<br>
to find the problematic equation?<br>
<br>
Thank you in advance<br>
_______________________________________________<br>
Cbc mailing list</font></tt><tt><font size=2 color=blue><u><br>
</u></font></tt><a href="mailto:Cbc@list.coin-or.org"><tt><font size=2 color=blue><u>Cbc@list.coin-or.org</u></font></tt></a><font size=3 color=blue><u><br>
</u></font><a href="http://list.coin-or.org/mailman/listinfo/cbc"><tt><font size=2 color=blue><u>http://list.coin-or.org/mailman/listinfo/cbc</u></font></tt></a><font size=3><br>
</font>
<br>
<br>