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<div class="moz-cite-prefix">Dear Zhanibev,<br>
<br>
1. I try to answer both of your questions at once:<br>
<br>
The definition of an integer in SCIP is:<br>
<br>
x is integer <=> x \in [ [x] - eps, [x] +eps ].<br>
The standard numeric epsilon is eps=10^-6 which gives you
reasonable integral values on most instances.<br>
<br>
If I'm not mistaken, SCIP already solved your integer problem
within an eps of 10^-12. <br>
<br>
Just for the sake of completeness: you can change the floating
epsilon from inside the SCIP interactive shell:<br>
set numerics epsilon 0.1<br>
<br>
2. Decreasing number of LP iterations<br>
<br>
I guess you are the very first to complain about a decrasing
number of LP iterations during the solve ;)<br>
The first reason is that at the first node (the root node),
SCIP solves a lot more LPs than at consecutive<br>
nodes during the cut-separation loop. The second reason is
that during branch-and-bound, <br>
not every node-LP needs to solved from scratch (i.e., by
feeding the node LP into the LP solver as a new <br>
problem).<br>
Basically, the LP relaxation at a node usually differs from
its parent node's LP relaxation by a single <br>
bound change, namely that of the variable branched on. The LP
basis information stays dually <br>
feasible and is quickly reoptimized (made primal feasible) by
a small number of dual simplex interations.<br>
This is called warm starting and should be almost always be
faster (in terms of the LP iteration count)<br>
than resolving the LP from scratch. <br>
SCIP solves the branch-and-bound tree by selecting nodes in a
depth-first-search like fashion (to some extent)<br>
to take advantage of fast warm starting.<br>
<br>
Regards<br>
Gregor<br>
<br>
Am 04.12.2013 06:55, schrieb Zhanibek Datbayev:<br>
</div>
<blockquote
cite="mid:CAOLxqifBrwqLnmJ-pGjjJh3UeQ9qR=4cQo7i3JSAM7mEXBuu_g@mail.gmail.com"
type="cite">
<div dir="ltr">Hey guys,
<div><br>
</div>
<div>I'm trying to tackle a MIP problem using SCIP. All of my
variables are either integer or binary, but sometimes SCIP
produces non-integer values. For example below all of the
values are integers except of one which gets
3491.99999999999. </div>
<div><br>
</div>
<div>Is that expected behavior? Should I not worry about this
kind of values and just convert them to integers (adding 0.1
before doing that)?</div>
<div><br>
</div>
<div>Thanks in advance!</div>
<div><br>
</div>
<div>-Zhanibek</div>
<div><br>
</div>
<div>
<div><br>
</div>
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<div><br>
</div>
</div>
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