[Scip] sepasol never executed

[Stefan Lörwald]

Hi,

thank you, Marc, for replying.

I don't think sepa_closecuts is suitable for my needs.

What I want to achieve is adding locally valid inequalities at each
branch decision. I thought that there is a SCIP_SOL for every branch,
but maybe I'm mistaken on how SCIP operates.
The inequality can only be added if two upper bounds on variables are
0, so it can't be added via SCIPcreateConsLinear and SCIPaddCons as
far as I know.

So basically the question boils down to "how to access the values and
bounds of a local solution and add constraints locally?".

2013/6/18 Marc Pfetsch <pfetsch at mathematik.tu-darmstadt.de>:
>
> 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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