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Date: Tue, 5 Sep 2006 17:15:42 -0400
From: "Yonik Seeley" <yonik@apache.org>
Sender: yseeley@gmail.com
To: java-dev@lucene.apache.org
Subject: Re: [jira] Updated: (LUCENE-584) Decouple Filter from BitSet
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References: <27200586.1149076109798.JavaMail.jira@brutus>
	 <16099236.1157403804350.JavaMail.jira@brutus>

On 9/4/06, Eks Dev (JIRA) <jira@apache.org> wrote:

> Here are some Matcher implementations,
>
> - OpenBitsMatcher- the same as the code Paul wrote for BitsMatcher, with replaced OpenBitSet instead
>
> -DenseOpenBitsMatcher  - Using solr BitSetIterator (for skipTo() to work, one method in BitSetIterator should become public)

Keep in mind that BitSetIterator is fast for iteration over all it's bits.
If it's used as a filter (with skipping), I would expect it to be slower.

> Also attached one simple  test (just basic fuctionality) that also contains one dummy relative performance  test
>
> Perf. test simply iterates over different Matcher implementations  and measures ellapsed time (not including Matcher creation, pure forward scan to the end) for different set bit densities.
>
> imho, this code is not sufficiantly tested nor commented, needs an hour or two.
>
> As expected, Yonik made this BitSetIterator really fast. What was surprise for me was OpenBitSet nextSetBit() comparing bad to the BitSet  (or I made some dummy mistake somewhere?)

That's weird... what CPU and in what mode (32 or 64 bit)?  What JVM params?
Do you get the same results from org.apache.solr.util.BitSetPerf for nextSetBit?

I did write it on a P4, and ntz (number of trailing zeros) is
currently optimized for a 32 bit CPU where a 64 bit shift may be
slightly more expensive.

-Yonik

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