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From "Han Jiang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (LUCENE-3892) Add a useful intblock postings format (eg, FOR, PFOR, PFORDelta, Simple9/16/64, etc.)
Date Sat, 02 Jun 2012 09:31:24 GMT

     [ 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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