Re: [rules-users] rules-users Digest, Vol 63, Issue 60
I don't understand either of these answers. All of the facts are in a list of facts
passed into ksession.execute, like this:
final StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
List<Object> facts = createPosts();
if (facts.size() == 0) break;
long t0 = System.currentTimeMillis()/100;
ksession.execute(facts);
long t1 = System.currentTimeMillis()/100;
System.out.println("Elapsed time: " + (t1 - t0));
There are no more facts getting created during rules processing. The whole drl file is:
rule "collect"
when
$a : ArrayList(size > 0) from collect(Post());
then
System.out.println("Number of posts: " + $a.size());
System.out.println("DONE");
end
Why is the collect happening more than once? Actually I don't think it is, else I
would be seeing more than one printout.
I agree that I could probably find a way to do without the list, but I would still like to
understand why this is n-squared. I was actually planning to explore the performance of
various ways to compute the minimum of a large number of objects. I was surprised to find
that I was already up to n-squared just creating the list.
> ------------------------------
>
> Message: 3
> Date: Mon, 13 Feb 2012 20:59:20 +0100
> From: Wolfgang Laun <wolfgang.laun(a)gmail.com>
> Subject: Re: [rules-users] Performance of collect seems to be
> n-squared
> To: Rules Users List <rules-users(a)lists.jboss.org>
> Message-ID:
> <CANaj1LeAnD-
> kYngQqTzo1XoOh4V8tnqo5A+9CkVR6xPmK4gxMA(a)mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Repeatedly creating this ArrayList is bound to be O(n2).
>
> Why do you want the Post facts as a List? There may be better ways for
> achieving your goal.
>
> -W
>
>
> On 13 February 2012 20:49, Shur, Bob <robert.shur(a)hp.com> wrote:
>
> > I have a simple class Post { int id; ... }. I insert some number of
> them
> > as facts and then call ksession.execute(facts);
> >
> > The whole drl file (except for package and import statements) is:
> >
> > rule "collect"
> > when
> > $a : ArrayList(size > 0) from collect(Post());
> > then
> > System.out.println("Number of posts: " + $a.size());
> > System.out.println("DONE");
> > end
> >
> > The time it takes to run is n-squared in the number of posts. For
> 4000,
> > 8000, 16000, 32000, 64000 posts the time is (in 1/10 seconds):
> >
> > 4, 14, 56, 220, 852
> >
> > Is this expected? Is there a better way for me to do the collect?
> >
> >
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> >
>