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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-2903) Improvement of PForDelta Codec
Date Wed, 16 Feb 2011 13:53:00 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-2903?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Muir updated LUCENE-2903:
--------------------------------

    Attachment: for_pfor.patch

Nice results Hao!

One idea for the low-frequency multitermqueries (foo* etc) could be in the attached patch:
i only implemented this for the existing FrameOfRef and PatchedFrameOfRef but perhaps you
could steal/test the idea with your implementation.

In these cases i switched them over to a single byte header instead of an int. 

This means less overhead per-block, a slightly smaller (maybe 1-2%?) index. It might be more
useful if we switch your codec over from Sep layout to interleaved (Fixed) layout, to make
a more efficient skipBlock()... but this interleaved layout is still a work in progress.


> Improvement of PForDelta Codec
> ------------------------------
>
>                 Key: LUCENE-2903
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2903
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: hao yan
>         Attachments: LUCENE-2903.patch, LUCENE-2903.patch, for_pfor.patch
>
>
> There are 3 versions of PForDelta implementations in the Bulk Branch: FrameOfRef, PatchedFrameOfRef,
and PatchedFrameOfRef2.
> The FrameOfRef is a very basic one which is essentially a binary encoding (may result
in huge index size).
> The PatchedFrameOfRef is the implmentation based on the original version of PForDelta
in the literatures.
> The PatchedFrameOfRef2 is my previous implementation which are improved this time. (The
Codec name is changed to NewPForDelta.).
> In particular, the changes are:
> 1. I fixed the bug of my previous version (in Lucene-1410.patch), where the old PForDelta
does not support very large exceptions (since
> the Simple16 does not support very large numbers). Now this has been fixed in the new
LCPForDelta.
> 2. I changed the PForDeltaFixedIntBlockCodec. Now it is faster than the other two PForDelta
implementation in the bulk branch (FrameOfRef and PatchedFrameOfRef). The codec's name is
"NewPForDelta", as you can see in the CodecProvider and PForDeltaFixedIntBlockCodec.
> 3. The performance test results are:
> 1) My "NewPForDelta" codec is faster then FrameOfRef and PatchedFrameOfRef for almost
all kinds of queries, slightly worse then BulkVInt.
> 2) My "NewPForDelta" codec can result in the smallest index size among all 4 methods,
including FrameOfRef, PatchedFrameOfRef, and BulkVInt, and itself)
> 3) All performance test results are achieved by running with "-server" instead of "-client"

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