Re: [eclipse-clp-users] Is referenced_record/2 related to accessing asserted clauses?

From: Edwin Wirawan <edcsgt_at_...32...>
Date: Mon, 26 Nov 2012 11:23:46 +0800
Thanks Kish and Thorsten for your help. I will try implementing your suggestions.

Regards,
Edwin

> Date: Fri, 23 Nov 2012 18:36:18 +0000
> From: kisshen@...5...
> To: eclipse-clp-users_at_lists.sourceforge.net
> Subject: Re: [eclipse-clp-users] Is referenced_record/2 related to accessing asserted clauses?
> 
> Hi Edwin,
> 
> I think the main point here is -- as Thorsten said -- dynamic clauses is 
> not the best way in ECLiPSe to do what you want.
> 
> On 23/11/2012 08:31, Edwin Wirawan wrote:
> 
> > I tried profiling a run of my code and the result showed that the majority of the time (~80%) is spent in referenced_record/2.
> >
> > My code asserts a lot of dynamic clauses at runtime and refers to these dynamic clauses regularly.
> >
> > Does referenced_record/2 spend most of its runtime accessing asserted clauses, or doing something else?
> 
> I assume you are running ECLiPSe 6.0 (or newer). The way dynamic 
> predicates are implemented was changed in that version, and it is now 
> implemented using the recorded database (record/2 and friends), and 
> referenced_record/2 is likely used to access the asserted clauses as you 
> suspect.
> 
> >
> > FYI, each asserted clause is of the form: edge(edgeN,
> > ...more content...), where edgeN is unique for each asserted edge clause (e.g., edge1, edge2,edge3,бн).
> >
> > ~200K such clauses are asserted during a typical run.
> >
> 
> It looks like your clauses are basically data, and as Thorsten said, it 
> is not efficient to uss dynamic clauses for this. The user manual has a 
> chapter on non-logical storage that discuss the various ways you can 
> store and access data non-logically.
> 
> A slight correction to Thorsten's comments -- dynamic clauses are 
> "indexed" to some extent, i.e. there is some filtering of clauses that 
> have the same name and arity, because recorded/2, which is used to 
> access the clause, does do some filtering, but as Thorsten shows, it is 
> not that effective when you have a large number of clauses.
> 
> 
> > A slightly related question: I also called statistics/1. There were
> > 200K+ dictionary_entries, dict_hash_usage showed that the dictionary was
> >   full (8192/8192) and the dict_has_collisions had a value of
> > (196801/8192).
> >
> >
> > My guess is that the majority of 200K+ dictionary entries correspond to
> >   our asserted 'edge' clauses, which leads me to wonder if the large
> > number of dictionary collisions means that the dictionary is using the
> > functor 'edge' or some other conflicted
> >   value as a key instead of my unique edge ID values. Does that seem
> > right? Would the dictionary hash function have any difficulty
> > distinguishing IDs that share a common substring such as 'edge', and
> > thus cause the seemingly high number of collisions?
> 
> I am guessing that your 'edge' id are implemented as atoms (as opposed 
> to strings), as I don't think strings goes into the dictionary (and are 
> not indexed, so using strings as unique ids is a bad idea).
> 
> I suspect if you have so many different ids, you may be better off using 
> integers (I assume you generate your 'edge' ids by combining an integer 
> with the atom edge anyway), as integers do not need to be added to the 
> dictionary, and I suspect they might index better than the atoms as well.
> 
> >
> > I am also wondering whether there is a way to inspect the structure and
> > content of the dictionary and the database of asserted clauses, and also
> >   whether there's a memory profiler for ECLiPSe.
> 
> I don't think there is anyway for a user to examine the dictionary. For 
> asserted clauses, you can using listing/1 to list the clauses, but this 
> would not give you any information on how well the filtering works.
> 
> Cheers,
> 
> Kish
> 
> 
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Received on Mon Nov 26 2012 - 03:23:53 CET

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