[Scip] sepasol never executed

[Marc Pfetsch]

Hi Stefan,

sepasol() ist only executed if you explicitly call SCIPseparateSol() for 
a given primal solution. This callback is used to generate cuts for 
solutions that do not arise from the usual LP-relaxation, e.g. if you 
have combinatorial dual program or the like.

As one example, you can try the closecuts-separator (by setting 
separating/closecuts/freq = 0). Here, a new solution is generated on the 
line segment between the current LP solution and either a primal 
feasible solution or an interior point (see the parameters for 
closecuts). This solution is then passed to SCIPseparateSol(), which 
then generates cuts. In many cases, this generates "stronger" cuts in 
some sense. Note, however, that this also might produce cuts that are 
not violated by the current LP solution and are thus discarded. See also

http://scip.zib.de/doc/html_devel/sepa__closecuts_8c.shtml

Best

Marc





On 06/18/2013 01:40 PM, Stefan Lörwald wrote:
> Dear SCIP community,
>
> I've implemented a custom constraint handler based on the Linear
> Ordering example. I actually only need sepasol, but it's never executed
> no matter what settings are chosen (SEPAFREQ, SEPAPRIORITY, DELAYSEPA).
> Going back to the example I've noticed that it's also never executed.
>
> Why is the method implemented if it's never used and _how_ to activate
> the usage?
>
> Yours,
> Stefan
>
>
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