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<div class="moz-cite-prefix">Dear Emmanuel,<br>
<br>
sorry for the late reply. The use of customized relaxations
requires the implementation of a relaxation handler. A quick
starting guide on how to do this can be found in our <a
href="http://scip.zib.de/doc/html/RELAX.php">HowTo section on
relaxation handlers</a>.<br>
<br>
The crux is, of course, how to handle additional objective
coefficients for every variable. This can be currently managed,
eg, by entering diving mode of SCIP, changing all variable
objective coefficients, and resolving the diving LP.<br>
Your relaxation should then also have a mechanism to store every
node's lower bound according to the <br>
additional objective.<br>
<br>
As far as I know, multiobjective problems are usually solved as a
series of weighted combinations of the objective functions. The
generation of such a sequence is easy to achieve by changing the
objective coefficients <br>
for all variables, and resolving the problem with SCIP. (Since
primal solutions stay feasible, you might consider transferring
them from one solving round to the next, as well).<br>
<br>
If everything works as planned, the next SCIP release will contain
more refined reoptimization techniques and a multiobjective solver
as an example.<br>
<br>
Hope this helps,<br>
Gregor<br>
<br>
Am 11.03.2015 um 15:54 schrieb Emmanuel Kieffer:<br>
</div>
<blockquote cite="mid:55005734.50705@gmail.com" type="cite">Hello,
<br>
<br>
I would like to know if it is technically possible to use SCIP to
<br>
perform a Bi-objective Branch and Bound?
<br>
If yes, I need to solve several relaxed problem at each nodes. So
far I
<br>
know, it's possible to deactivate the standard LP relaxation and
use a
<br>
custom one but how is it work?
<br>
<br>
<br>
Thank you
<br>
<br>
Best regards,
<br>
<br>
Emmanuel
<br>
<br>
<br>
<br>
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</blockquote>
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