<div dir="ltr">Hi guys,<div><br></div><div>Sorry to be bugging you about this again but looking it closer, it appears that even an output can be successful like this</div><div><br></div><div><div>------------------------------------------------------------------</div>
<div> This is CBC v2.8.8</div><div> Author: John J. Forrest</div><div><br></div><div> Problem Properties:</div><div> # Decision Variables: 2730 [0 Integer, 945 Binary]</div><div> # Linear Constraints: 2829 [12294 nz]</div>
<div>------------------------------------------------------------------</div><div>Pass 1: suminf. 0.56051 (3) obj. -0.0501974 iterations 260</div><div><br></div><div> *** SUCCESSFUL TERMINATION ***</div><div> Objective Value: 1e+50</div>
<div> Gap: 1e+50 (100.00%)</div><div> Searched: 4 nodes [1506 LP iterations]</div><div>------------------------------------------------------------------</div></div><div><br></div><div>looking at the values of x, the ones I set to be binary become real (satisfying all my linear constraints). Is anyone aware of under what circumstances could this happen?</div>
<div><br></div><div>Thanks</div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Feb 17, 2014 at 9:35 PM, Petros Karasakalidis <span dir="ltr"><<a href="mailto:petkaras@gmail.com" target="_blank">petkaras@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Giacomo,<div><br></div><div>Thanks for looking at this. The Matlab interface is using the C++ version of the cbc as is, so I m not sure if it really matters.</div>
<div><br></div><div>What is interesting is that when I know whether a problem is infeasible the output of the function is correctly as follows:</div><div class="">
<div><br></div><div>------------------------------------------------------------------</div><div> This is CBC v2.8.8</div><div> Author: John J. Forrest</div><div><br></div><div> Problem Properties:</div><div> # Decision Variables: 2730 [0 Integer, 945 Binary]</div>
<div> # Linear Constraints: 2830 [13013 nz]</div><div>------------------------------------------------------------------</div><div><br></div></div><div> *** TERMINATION: LINEAR RELAXATION INFEASIBLE ***</div><div> Objective Value: 1.79769e+308</div>
<div> Gap: 1.79769e+308 (100.00%)</div><div> Searched: 0 nodes [0 LP iterations]</div><div>------------------------------------------------------------------ </div><div><br></div><div>What makes it a little further tricky and makes me think there is a bug here is that in my test run (for which I have the inputs in the dropbox link above) I get an fval of sth like 1e+50 whereas the f'*x is sth like 0.5011 which is more close to reality. However, I know that the resulting x is not right because even though satisfies all my constraints, it does converts my binary variables to reals and gives me this following (repeating the previous output here).</div>
<div class="">
<div><br></div><div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif">------------------------------------------------------------------</font></div><div style="font-family:arial,sans-serif;font-size:13px">
<font color="#000000" face="Arial, Helvetica, sans-serif"> This is CBC v2.8.8</font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> Author: John J. Forrest</font></div>
<div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"><br></font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> Problem Properties:</font></div>
<div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> # Decision Variables: 2730 [0 Integer, 945 Binary]</font></div><div style="font-family:arial,sans-serif;font-size:13px">
<font color="#000000" face="Arial, Helvetica, sans-serif"> # Linear Constraints: 2830 [13013 nz]</font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif">------------------------------------------------------------------</font></div>
<div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif">Pass 1: suminf. 0.81917 (8) obj. -0.0499381 iterations 198</font></div><div style="font-family:arial,sans-serif;font-size:13px">
<font color="#000000" face="Arial, Helvetica, sans-serif"><br></font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> *** SUCCESSFUL TERMINATION ***</font></div>
<div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> Objective Value: 1e+50</font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> Gap: 1e+50 (100.00%)</font></div>
<div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"> Searched: 0 nodes [223 LP iterations]</font></div><div style="font-family:arial,sans-serif;font-size:13px">
<font color="#000000" face="Arial, Helvetica, sans-serif">------------------------------------------------------------------</font></div></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif"><br>
</font></div></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif">Any further feedback/clue would be greatly appreciated.</font></div><div style="font-family:arial,sans-serif;font-size:13px">
<font color="#000000" face="Arial, Helvetica, sans-serif"><br></font></div><div style="font-family:arial,sans-serif;font-size:13px"><font color="#000000" face="Arial, Helvetica, sans-serif">Thanks</font></div></div><div class="HOEnZb">
<div class="h5"><div class="gmail_extra">
<br><br><div class="gmail_quote">On Mon, Feb 17, 2014 at 6:47 PM, Giacomo Nannicini <span dir="ltr"><<a href="mailto:giacomo.n@gmail.com" target="_blank">giacomo.n@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
I never used the Matlab interface, but looking at the output, it seems<br>
that the LP relaxation of the problem is infeasible (look at the sum<br>
of infeasibilities).<br>
"Successful termination" probably just means that there was no error,<br>
but the problem has no feasible solution anyway. If you think that<br>
there must be a feasible solution, I'd suggest checking your data.<br>
<br>
Giacomo<br>
<div><div><br>
On Tue, Feb 18, 2014 at 9:56 AM, Petros Karasakalidis<br>
<<a href="mailto:petkaras@gmail.com" target="_blank">petkaras@gmail.com</a>> wrote:<br>
> Hi all,<br>
><br>
> I am forwarding this email here as I m not sure my previous email went<br>
> through since I cannot see it on the active tickets. Any help would be<br>
> greatly appreciated.<br>
><br>
> Thanks<br>
><br>
> ---------- Forwarded message ----------<br>
> From: Petros Karasakalidis <<a href="mailto:petkaras@gmail.com" target="_blank">petkaras@gmail.com</a>><br>
> Date: Sat, Feb 15, 2014 at 8:21 PM<br>
> Subject: CBC<br>
> To: <a href="mailto:cbc-tickets@list.coin-or.org" target="_blank">cbc-tickets@list.coin-or.org</a><br>
><br>
><br>
> I use CBC through the opti toolbox (having Matlab as an interface) in order<br>
> to solve a MILP problem. Everything was working until the point I used as<br>
> inputs the data I have here<br>
><br>
> <a href="https://www.dropbox.com/s/qwg4x50bcrhq066/cbc_inputs.xlsx" target="_blank">https://www.dropbox.com/s/qwg4x50bcrhq066/cbc_inputs.xlsx</a><br>
><br>
><br>
> The file is about 20MB and wouldnt fit into this email. For some reason, the<br>
> objective results into a very large number (like 1e+50) while the status<br>
> output shows success as follows:<br>
><br>
> ------------------------------------------------------------------<br>
> This is CBC v2.8.8<br>
> Author: John J. Forrest<br>
><br>
> Problem Properties:<br>
> # Decision Variables: 2730 [0 Integer, 945 Binary]<br>
> # Linear Constraints: 2830 [13013 nz]<br>
> ------------------------------------------------------------------<br>
> Pass 1: suminf. 0.81917 (8) obj. -0.0499381 iterations 198<br>
><br>
> *** SUCCESSFUL TERMINATION ***<br>
> Objective Value: 1e+50<br>
> Gap: 1e+50 (100.00%)<br>
> Searched: 0 nodes [223 LP iterations]<br>
> ------------------------------------------------------------------<br>
><br>
> Would appreciate any feedback or direction towards the solution. Feel free<br>
> to ask any questions that might be helpful.<br>
><br>
> Thanks<br>
><br>
><br>
</div></div>> _______________________________________________<br>
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><br>
</blockquote></div><br></div>
</div></div></blockquote></div><br></div>