[SCIP] Custom branching -- catching an assert

[Gerald Gamrath]

Dear Albert,

changing the upper bound to 0 to enforce your decision is correct. 
However, your consactive method should only mark the constraint to be 
repropagated; afterwards, propagation will be called where you should 
adjust the bounds. Since the bound is only changed at the current node, 
SCIP will automatically undo this when the current subtree is left and 
re-install the bound when it is re-entered. In the latter case, you thus 
only need to propagate variables added in the meantime.

For more details, see 
https://scip.zib.de/doc-6.0.2/html/FAQ.php#pricerandnodedata or have a 
look at the binpacking example.

Best,
Gerald

Am 09.01.20 um 10:45 schrieb Schrotenboer, Albert:
> Dear SCIP Community,
>
> I am solving a basic VRP with branch & price, and have a question 
> regarding a branching rule I've implemented (Actually, I forgot how to 
> do it...) I branch on x_{ij} arcs, which I identify with my branchrule 
> object. To handle this information down the b&b tree, I use a 
> constraint handler with the following virtual methods implemented:
>
> SCIP_DECL_CONSTRANS(ObjConshdlrOwn::scip_trans)
>       To transform the info, nothing special
> SCIP_DECL_CONSACTIVE(ObjConshdlrOwn::scip_active)
>       Here I search which of my generated routes should be fixed to 
> zero corresponding to my branching information. (I also do the 
> appropriate adaptations in my pricing based on the branching). I fix 
> my variables by the following routines:
>
> if (SCIPvarGetUbLocal(var) > 0.01)
>       SCIP_CALL(SCIPchgVarUb(scip, (*d_varConsInfo).v_path[r].d_var, 
> 0.0) );
>
> This all works nicely (when I do not run in debug mode). When I run in 
> Debug mode, however, an assert is collapsing when SCIP alters the path 
> of the tree (when it backtracks a few nodes), saying that:
> JRP: src/scip/tree.c:1803: SCIPnodeAddBoundinfer: Assertion 
> `(SCIP_NODETYPE)node->nodetype == SCIP_NODETYPE_FOCUSNODE || 
> (SCIP_NODETYPE)node->nodetype == SCIP_NODETYPE_PROBINGNODE || 
> (SCIP_NODETYPE)node->nodetype == SCIP_NODETYPE_CHILD || 
> (SCIP_NODETYPE)node->nodetype == SCIP_NODETYPE_REFOCUSNODE || 
> node->depth == 0' failed.
>
> My question is, therefore, the following: Is changing the UB to 
> enforce variables to 0 the correct way to go? In addition, am I 
> required to implement the deactive virtual method as well, to change 
> the upper bounds back to what they were?
>
> Kind regards,
> Albert
>
> -- 
>
> Albert Schrotenboer
>
> Postdoctoral Researcher
>
> Faculty of Economics and Business
>
> University of Groningen
>
> P.O. Box 800, 9700 AV Groningen
>
>
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