[Scip] Set a primal solution

[michael.winkler@zib.de]

Hi Rostislav,

you can write a heuristic plugin setting the timing to
SCIP_HEURTIMING_BEFOREPRESOL. This heuristic will then be called only
before presolving of the whole problem (might be multiple times when a
restart happens).
Take a look at the heur_trivial.c for further details.

When creating a solution via SCIPcreateSol() the solution vector will
contain zero values for all variables implicitly.

You then need to use SCIPsetSolVal()/SCIPsetSolVals() to set solution
values for the variables.

Afterwards please use SCIPtrySol()/SCIPtrySolFree() which will check the
correctness of the solution and if so SCIP will store the solution and
also update the primalbound and cutoffbound. (So, there is no need to add
you extra "bound constraint" anymore, when adding a solution.)

Please take a look at:
http://scip.zib.de/doc/html/HEUR.shtml
http://scip.zib.de/doc/html/scip_8h.shtml#a03da404f4153d8f673e87fb28bc7d552
http://scip.zib.de/doc/html/scip_8h.shtml#adbb9f3c0c0b462481fe5eff677463258
http://scip.zib.de/doc/html/scip_8h.shtml#ab4007453cafad788430c2ad55129479f
http://scip.zib.de/doc/html/scip_8h.shtml#ae4041777d638e0bcbbb592946b520f15
http://scip.zib.de/doc/html/scip_8h.shtml#af00de2379f996445b4497db79e7449f0

Best, Michael

> Dear SCIP community,
> I excuse me for this question which should be clear for me, but how
> should I correctly set a primal solution before starting the solving
> process? I solve an ILP using the SCIP solver and before starting the
> process I would like to set a heuristical primal solution which would
> also define a bound (this heuristic should not be called during the
> solving process more). I set the bound as a global constraint, but I do
> not know how to set the solution. Can I use “SCIPcreateSol”? And what
> does it mean “creates a primal solution, initialized to zero”?
> Thank you very much in advance.
> Yours faithfully,
> Rostislav Stanek
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