[SCIP] Processed / open / pruned nodes

[Lara Scavuzzo]

Dear Gregor,


Thank you very much for your detailed explanation. As you suggested, I used
the ncreatednodesrun counter, although I think you meant to write

<pruned nodes> = scip->stat->ncreatednodesrun - SCIPgetNNodes() - (
SCIPgetNChildren() + SCIPgetNLeaves() + SCIPgetNSiblings() )


If I may ask for one last clarification: from what you write I understand
that the children/siblings/leaves distinction is made based on the depth of
each open node with respect to the focus node. Is this correct?


Thank you again.


Best,


Lara

El jue., 25 jul. 2019 a las 14:46, Gregor Hendel (<hendel at zib.de>) escribió:

> Hi Lara,
>
> the tree maintains three different types of open nodes: children,
> siblings, and leaves. The types are always relative to the focus node. It
> is correct that SCIPgetNNodes() returns the total number of processed
> nodes, ie, the nodes which have been focussed during the search so far.
>
> The number of currently open nodes can therefore be accessed as the sum
> SCIPgetNChildren() + SCIPgetNSiblings() + SCIPgetNLeaves()
>
> SCIPgetNFeasibleLeaves() and SCIPgetNInfeasibleLeaves() are referring to
> leaves from hindsight, i.e., they count how often the search encountered
> nodes where the relaxation was feasible (e.g, all variables integer) and
> how often a focus
> node was pruned (either the relaxation hit the objective limit, or the
> node represents an infeasible subproblem).
> On the contrary, SCIPgetNLeaves() reports the current number of leaf nodes
> in the queue, not the total number of leaf nodes.
>
> It is not possible in the current SCIP version to access the number of
> pruned nodes. If nodes are pruned from the queue, e.g., because a new
> incumbent solution has been found, this happens silently at the solver's
> discretion.
>
> There is a counter for the number of created nodes, which is not publicly
> accessible via methods.
>
> scip->stat->ncreatednodesrun
>
> You can (ab)use this counter to get the number of pruned nodes by the
> equation
>
> <pruned nodes> = scip->stat->ncreatednodesrun - SCIPgetNNodes() -
> SCIPgetNChildren() + SCIPgetNLeaves() + SCIPgetNSiblings()
>
> I don't see a reason why there is no public method to access this
> attribute of the stats struct, I suggest you add one, that you can wrap
> from the Python Interface in a second step.
>
> Hope this helps,
> Gregor
>
>
> Am 25.07.19 um 13:21 schrieb Lara Scavuzzo Montana:
>
> Dear SCIP community,
>
>
> I am solving MILPs using SCIP’s Python interface with all default
> parameters and a custom branching rule. I am a bit confused by the
> terminology of the documentation, so I would be very thankful for the
> following clarifications.
>
>
> During the solving process, I would like to keep track of some solving
> statistics. In particular, at each step know:
>
> - *The number of processed nodes:* this can be accessed with (correct me
> if I am wrong) SCIPgetNNodes().
>
> - *The number of open nodes:* is SCIPnodepqlen() the right function to
> call?
>
> - *The number of pruned nodes* (by bound, infeasibility or integrality):
> I was unfortunately unable to find a way to obtain this value. Would it be
> (# of leaves) - (# of open nodes) ?
>
>
> I was also surprised to see that
>
> SCIPgetNLeaves() != SCIPgetNFeasibleLeaves() + SCIPgetNInfeasibleLeaves()
>
> Maybe I am misinterpreting the meaning of these.
>
>
> Just to clarify, I would of course be modifying the Python interface to
> include all necessary functions.
>
>
> Thank you in advance for any help with this issue.
>
>
> Best,
>
>
> Lara Scavuzzo
>
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