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Posted to dev@lucene.apache.org by "Han Jiang (JIRA)" <ji...@apache.org> on 2012/06/02 11:31:24 UTC
[jira] [Updated] (LUCENE-3892) Add a useful intblock postings
format (eg, FOR, PFOR, PFORDelta, Simple9/16/64, etc.)
[ https://issues.apache.org/jira/browse/LUCENE-3892?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Han Jiang updated LUCENE-3892:
------------------------------
Attachment: LUCENE-3892_pfor.patch
Here is a initial implementation of PForPostingsFormat. It is registered in oal.codecs.mockrandom.MockRandomPostingsFormat, and all tests have passed (Maybe I should modify some other mock files as well?).
This version is orginally inspired by the pfor and pfor2 impls in bulk_branch, mostly by the idea of pfor. Currently, the compressed data consists of three parts: header, normal area, and excpetion area. The normal area encodes each small value as b bits, as well as exception values. The exception area stores each large value directly, possibly as 8,16,or 32 bits. NumFrameBits range from 1-32 are all supported.
I haven't test the performance, but there are some known bottlenecks: For example, data = {0, 0xffffffff, 0, 1, 0, 1, 0}, numFrameBits=1, then the following '1's will be forced as exceptions, which will dramatically increase compressed size.
> Add a useful intblock postings format (eg, FOR, PFOR, PFORDelta, Simple9/16/64, etc.)
> -------------------------------------------------------------------------------------
>
> Key: LUCENE-3892
> URL: https://issues.apache.org/jira/browse/LUCENE-3892
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Michael McCandless
> Labels: gsoc2012, lucene-gsoc-12
> Fix For: 4.1
>
> Attachments: LUCENE-3892_pfor.patch, LUCENE-3892_settings.patch, LUCENE-3892_settings.patch
>
>
> On the flex branch we explored a number of possible intblock
> encodings, but for whatever reason never brought them to completion.
> There are still a number of issues opened with patches in different
> states.
> Initial results (based on prototype) were excellent (see
> http://blog.mikemccandless.com/2010/08/lucene-performance-with-pfordelta-codec.html
> ).
> I think this would make a good GSoC project.
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