Sorry, I meant "SolveMasterAsIp = 0".<br><br>See DecompParam.h for the list of parameters (and some comments).<br><br><br><br><div class="gmail_quote">On Tue, Oct 12, 2010 at 8:49 AM, Matthew Galati <span dir="ltr"><<a href="mailto:magh@lehigh.edu">magh@lehigh.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi Kim,<br><br>To shut off the heuristic, use:<br><br>[DECOMP]<br>SolutionMasterAsIp = 0<br>
<br>Please send me instructions on how to repeat the issue and I will investigate. <br><br>Thanks,<br>Matt<br><br><br><br><div class="gmail_quote"><div><div></div><div class="h5">
On Tue, Oct 12, 2010 at 7:25 AM, kim <span dir="ltr"><<a href="mailto:kim@hamilton-vejlin.dk" target="_blank">kim@hamilton-vejlin.dk</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div><div></div><div class="h5">
<div bgcolor="#ffffff" text="#000000">
I have now updated to trunk and no longer get the CBC errors. I am
sometimes getting warnings about slightly violated constraints but more
seriously I am often getting an infeasibility error when I am nearing
termination of MILPBlock. I get the following error message:<br>
<br>
"Solve as IP found a solution.<br>
COIN Exception [ Recomposed solution is not feasible ] at
../../../Dip/src/DecompAlgoPC.cpp:L815 in
DecompAlgoPC::solutionUpdateAsIp"<br>
<br>
Inspecting the code it seems this happens when solving the restricted
master as an IP. I have turned up the log levels, but don't know
MILPBlock/DIP well enough to make sense of it. I didn't want to clutter
up the mailing list with long output transcripts, but I can email you
the last bit of output if you like.<br>
<br>
It seems to me the easiest temporary fix for me would be to disable the
upper bound heuristic. Is there a way to do this in the parameter file
or would I need to modify my copy of the DIP code?<br><font color="#888888">
<br>
- Kim</font><div><div></div><div><br>
<br>
<br>
Matthew Galati wrote:
<blockquote type="cite">
<blockquote type="cite">
<pre>I'm a bit puzzled by this. CBC 2nd status=7 means the LP-relaxation is
unbounded (according to "CbcModel.hpp"). But the pricing problems
generated in my modified block file are all 0-1 Knapsack Problems and
should never be unbounded, unless the upper bound is also relaxed along
with the integrality requirement for some reason.
</pre>
</blockquote>
<pre>[MVG] Right. If it does return that for one of your knapsack problems -- then it is a CBC bug.
Turn up the log levels to see when that happens:
[DECOMP]
LogDebugLevel = 3
LogLevel = 3
LogDumpModel = 2
LogLpLevel = 1
</pre>
<blockquote type="cite">
<pre>Is CBC used for anything besides pricing problems? Your dissertation
mentions solving the restricted master problem to optimality to obtain
valid upper bounds (assuming minimization), so I would assume CBC could
also be used here.
</pre>
</blockquote>
<pre>[MVG] Yes - it is also used to solve the master problem as an IP. That is, it periodically changes the variables in the master problem (lambda) to integers and solves the master as an integer program. This is a heuristic to try and get incumbent solutions for the entire problem. This, in my thesis, is called Price-and-Branch.
Let me know if it is failing in the subproblem or the master IP.
</pre>
</blockquote>
<br>
</div></div></div>
<br></div></div><div class="im">_______________________________________________<br>
Dip mailing list<br>
<a href="mailto:Dip@list.coin-or.org" target="_blank">Dip@list.coin-or.org</a><br>
<a href="http://list.coin-or.org/mailman/listinfo/dip" target="_blank">http://list.coin-or.org/mailman/listinfo/dip</a><br></div></blockquote></div><br>
</blockquote></div><br>