lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Michael McCandless" <luc...@mikemccandless.com>
Subject Re: Token termBuffer issues
Date Wed, 25 Jul 2007 15:30:45 GMT
"Yonik Seeley" <yonik@apache.org> wrote:
> On 7/25/07, Michael McCandless <lucene@mikemccandless.com> wrote:
> > "Yonik Seeley" <yonik@apache.org> wrote:
> > > On 7/24/07, Michael McCandless <lucene@mikemccandless.com> wrote:
> > > > "Yonik Seeley" <yonik@apache.org> wrote:
> > > > > On 7/24/07, Michael McCandless <lucene@mikemccandless.com>
wrote:
> > > > > > OK, I ran some benchmarks here.
> > > > > >
> > > > > > The performance gains are sizable: 12.8% speedup using Sun's
JDK 5 and
> > > > > > 17.2% speedup using Sun's JDK 6, on Linux.  This is indexing
all
> > > > > > Wikipedia content using LowerCaseTokenizer + StopFilter +
> > > > > > PorterStemFilter.  I think it's worth pursuing!
> > > > >
> > > > > Did you try it w/o token reuse (reuse tokens only when mutating,
not
> > > > > when creating new tokens from the tokenizer)?
> > > >
> > > > I haven't tried this variant yet.  I guess for long filter chains the
> > > > GC cost of the tokenizer making the initial token should go down as
> > > > overall part of the time.  Though I think we should still re-use the
> > > > initial token since it should (?) only help.
> > >
> > > If it weren't any slower, that would be great... but I worry about
> > > filters that need buffering (either on the input side or the output
> > > side) and how that interacts with filters that try and reuse.
> >
> > OK I will tease out this effect & measure performance impact.
> >
> > This would mean that the tokenizer must not only produce new Token
> > instance for each term but also cannot re-use the underlying char[]
> > buffer in that token, right?
> 
> If the tokenizer can actually change the contents of the char[], then
> yes, it seems like when next() is called rather than next(Token), a
> new char[] would need to be allocated.

Right.  So I'm now testing "reuse all" vs "tokenizer makes a full copy
but filters get to re-use it".

> >  EG with mods for CharTokenizer I re-use
> > its "char[] buffer" with every Token, but I'll change that to be a new
> > buffer for each Token for this test.
> 
> It's not just for a test, right?  If next() is called, it can't reuse
> the char[].  And there is no getting around the fact that some
> tokenizers will need to call next() because of buffering.

Correct -- the way I'm doing this now is in TokenStream.java I have a
default "Token next()" which calls "next(Token result)" but makes a
complete copy before returning it.  This keeps full backwards
compatiblity even in the case where a consumer wants a private copy
(calls next()) but the provider only provides the "re-use" API
(next(Token result)).

Mike

---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org


Mime
View raw message