Re: error out of global stack prolog

Hi Batselem, Jan,

It's not straightforward how one would calculate the number of distinct
triples accros multiple graphs, e.g.:
~~~
?- rdf_assert(rdf:a, rdf:b, rdf:c, g1).
?- rdf_assert(rdf:a, rdf:b, rdf:c, g2).
?- rdf_statistics(triples(T)).
T = 2.
~~~
Or is there another way?

---
Cheers!,
Wouter Beek.

E-mail: [email protected]
WWW: www.wouterbeek.com
Tel.: 0647674624


On Thu, Jan 9, 2014 at 9:56 AM, Wielemaker, J. <[email protected]> wrote:

> On 01/09/2014 01:59 AM, atom meta wrote:
> > Hi, I am currently learning Prolog. when I apply a query such as
> >  findall(A, rdf(A,_,_), Y), length(Y, L), prolog throws out of global
> > stack, error. How could I fix this problem?
>
> You are creating a list with all subjects.  If you have a really big
> RDF store, that costs a lot of memory.  There are some options:
>
>   - Raise the stack limit using set_prolog_stack/2.
>   - Use aggregate_all(count, rdf(_,_,_), Triples).
>   - Use rdf_statistics(triples(Triples)).
>
> For really counting the triples, the latter is the best (it just
> looks up the number that is maintained in the store).  In similar
> cases you may need to do one of the first two.
>
>         Success --- Jan
>
> >
> > Thank you,
> > Batselem Jagvaral
> >
> >
> >
> >
> > 2 ?- findall(A, rdf(A,_,_), Y), length(Y, L).ERROR: Out of global stack
> >    Call: (13) rdf_db:rdf_update_duplicates_thread ? No previous search
> >    Call: (13) rdf_db:rdf_update_duplicates_thread ? No previous search
> >    Call: (13) rdf_db:rdf_update_duplicates_thread ? creep
> > ^  Call: (14) thread_create(rdf_update_duplicates, _G75, [detached(true),
> > alias('__rdf_duplicate_detecter')]) ? creep
> > ^  Exit: (14) thread_create(rdf_update_duplicates,
> > '__rdf_duplicate_detecter', [detached(true),
> > alias('__rdf_duplicate_detecter')]) ?
> >    Call: (1) rdf_db:rdf_update_duplicates ? creep
> > |:
> >    Exit: (13) rdf_db:rdf_update_duplicates_thread ?
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