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From John Wang <john.w...@gmail.com>
Subject Re: lucene 2.9 sorting algorithm
Date Fri, 23 Oct 2009 02:35:02 GMT
Mark:
       Please be patient with me. I am seeing a difference and was wondering
if Mike would see the same thing. I thought Michael would be willing to
because he expressed interest in understanding what the performance
discrepancies are.

       Again, it is only a request. It is perfectly fine if Michael refuses
to. But it would be great if Michael speaks for himself.

Thanks

-John

On Thu, Oct 22, 2009 at 7:29 PM, Mark Miller <markrmiller@gmail.com> wrote:

> Why? What might he find? Whats with the cryptic request?
>
> Why would Java 1.5 perform better than 1.6? It erases 20 and 40% gains?
>
> I know point 2 certainly doesn't. Cards on the table?
>
> John Wang wrote:
> > Hey Michael:
> >
> >        Would you mind rerunning the test you have with jdk1.5?
> >
> >        Also, if you would, change the comparator method to avoid
> > brachning for int and string comparators, e.g.
> >
> >
> >       return index.order[i.doc] - index.order[j.doc];
> >
> >
> > Thanks
> >
> >
> > -John
> >
> >
> > On Thu, Oct 22, 2009 at 2:38 AM, Michael McCandless
> > <lucene@mikemccandless.com <mailto:lucene@mikemccandless.com>> wrote:
> >
> >     On Thu, Oct 22, 2009 at 2:17 AM, John Wang <john.wang@gmail.com
> >     <mailto:john.wang@gmail.com>> wrote:
> >
> >     >      I have been playing with the patch, and I think I have some
> >     information
> >     > that you might like.
> >     >      Let me spend sometime and gather some more numbers and
> >     update in jira.
> >
> >     Excellent!
> >
> >     >      say bottom has ords 23, 45, 76, each corresponding to a
> >     string. When
> >     > moving to the next segment, you need to make bottom to have ords
> >     that can be
> >     > comparable to other docs in this new segment, so you would need
> >     to find the
> >     > new ords for the values in 23,45 and 76, don't you? To find it,
> >     assuming the
> >     > values are s1,s2,s3, you would do a bin. search on the new val
> >     array, and
> >     > find index for s1,s2,s3.
> >
> >     It's that inversion (from ord->Comparable in first seg, and
> >     Comparable->ord in second seg) that I'm trying to avoid (w/ this new
> >     proposal).
> >
> >     > Which is 3 bin searches per convert, I am not sure
> >     > how you can short circuit it. Are you suggesting we call
> >     Comparable on
> >     > compareBottom until some doc beats it?
> >
> >     I'm saying on seg transition you indeed get the Comparable for
> current
> >     bottom, but, don't attempt to invert it.  Instead, as seg 2 finds a
> >     hit, you get that hit's Comparables and compare to bottom.  If it
> >     beats bottom, it goes into the queue.  If it does not, you use the
> ord
> >     (in seg 2's ord space) to "learn" a bottom in the ord space of seg 2.
> >
> >     > That would hurt performance I lot though, no?
> >
> >     Yeah I think likely it would, since we're talking about a binary
> >     search on transition VS having to do possibly many
> >     upgrade-to-Comparable and compare-Comparabls to slowly learn the
> >     equivalent ord in the new segment.  I was proposing it for cases
> where
> >     inversion is very difficult.  But realistically, since you must keep
> >     around the ful ord -> Comparable for every segment anyway (in order
> to
> >     merge in the end), inversion shouldn't ever actually be "difficult"
> --
> >     it'd just be a binary search on presumably in-RAM storage.
> >
> >     Mike
> >
> >     ---------------------------------------------------------------------
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> >
> >
>
>
> --
> - Mark
>
> http://www.lucidimagination.com
>
>
>
>
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