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<div class="moz-cite-prefix">Matthew,<br>
<br>
Should be easy to fix - looks like a really stupid bug.<br>
<br>
If I change the lower bounds on y,z to 2,1 it works! As rounding
up should be first thing that happens, you can see why I say
stupid.<br>
<br>
John Forrest<br>
<br>
On 30/07/14 16:20, Matthew Gidden wrote:<br>
</div>
<blockquote
cite="mid:CAHRdPFyWkqqXUY-nPQbF4N6LGJj6zm=kM3ARCvmg7Kbh4siTZg@mail.gmail.com"
type="cite">
<div dir="ltr">Hi all,
<div><br>
</div>
<div>I've been posting a lot recently.. first of all, thank you
for replying!</div>
<div><br>
</div>
<div>I've unit tested my application pretty vigorously, and a
Cbc API unit test broke when I moved to the CLI
implementation. Specifically, I set up the following toy
problem:</div>
<div><br>
</div>
<div>min 2x + 0.5y + 1.8z</div>
<div>st x + y > 4.4</div>
<div> y + z < 3.1</div>
<div>x in [1.3, 5], y in [1.7, 5], z in [0.4, 5]</div>
<div>y, z integer<br clear="all">
<div><br>
</div>
<div>The unit test originally passed using the
OsiCbcSolverInterface's initial solve and branch and bound
methods. I updated it to use an OsiClpSolverInterface that
is fed a CbcModel and call CbcMain0/1 on said model. The
unit test now fails with the following relevant output:</div>
<div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Welcome
to the CBC MILP Solver <br>
Version: 2.8.7 <br>
Build Date: Dec 28 2013 <br>
command line - exchng -solve -quit (default strategy 1)<br>
Continuous objective value is 5.47 - 0.00 seconds<br>
Cgl0000I Cut generators found to be infeasible! (or
unbounded)<br>
Pre-processing says infeasible or unbounded</blockquote>
</div>
<div><br>
</div>
<div>To double check that indeed a feasible solution existed,
I solved the maximization form of the same instance.
Attached are MPS files for the max and min forms, and I have
verified the same behavior using the cbc CLI (i.e., min is
returned as infeasible and max solves). </div>
<div><br>
</div>
<div>I'm curious if anyone can replicate this and/or has any
advice.</div>
<div><br>
</div>
<div>Cheers,</div>
<div><br>
</div>
-- <br>
<div dir="ltr">Matthew Gidden<br>
Ph.D. Candidate, Nuclear Engineering
<div>
The University of Wisconsin -- Madison<br>
Ph. 225.892.3192<br>
</div>
</div>
</div>
</div>
<br>
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