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From "Toke Eskildsen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-1990) Add unsigned packed int impls in oal.util
Date Mon, 01 Mar 2010 14:13:05 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Toke Eskildsen updated LUCENE-1990:
-----------------------------------

    Attachment: LUCENE-1990-te20100301.patch
                performance-20100301.txt

I've tested on two 32 bit Windows machines: An Intel T2400 (32 bit only) running XP and an
Athlon X2 4850e (64 bit capable) running 32 bit XP. The result can be seen in attachment performance-20100301.txt.
Something curious happens with high (32+) bits/value for the T2400 as aligned overtakes packed.
However, the overall picture is still that aligned only wins for a few special cases, so now
I'll be happy to remove it from the patch. As a note, generated is also slower than packed
on the AMD processor, although not as much as for Intel.

I have removed all traces of aligned from PackedInts, but kept the classes in the patch, in
the case that someone finds a faster way to handle aligned. PackedIntsPerformance still includes
both the generated switch-implementation and Aligned32 and Aligned64. It should be possible
to apply the patch without Aligned32, Aligned64, AlignedWriter and PackedIntsPerformance.

> Add unsigned packed int impls in oal.util
> -----------------------------------------
>
>                 Key: LUCENE-1990
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1990
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: Flex Branch
>            Reporter: Michael McCandless
>            Priority: Minor
>             Fix For: Flex Branch
>
>         Attachments: generated_performance-te20100226.txt, LUCENE-1990-te20100122.patch,
LUCENE-1990-te20100210.patch, LUCENE-1990-te20100212.patch, LUCENE-1990-te20100223.patch,
LUCENE-1990-te20100226.patch, LUCENE-1990-te20100226b.patch, LUCENE-1990-te20100226c.patch,
LUCENE-1990-te20100301.patch, LUCENE-1990.patch, LUCENE-1990_PerformanceMeasurements20100104.zip,
perf-mkm-20100227.txt, performance-20100301.txt, performance-te20100226.txt
>
>
> There are various places in Lucene that could take advantage of an
> efficient packed unsigned int/long impl.  EG the terms dict index in
> the standard codec in LUCENE-1458 could subsantially reduce it's RAM
> usage.  FieldCache.StringIndex could as well.  And I think "load into
> RAM" codecs like the one in TestExternalCodecs could use this too.
> I'm picturing something very basic like:
> {code}
> interface PackedUnsignedLongs  {
>   long get(long index);
>   void set(long index, long value);
> }
> {code}
> Plus maybe an iterator for getting and maybe also for setting.  If it
> helps, most of the usages of this inside Lucene will be "write once"
> so eg the set could make that an assumption/requirement.
> And a factory somewhere:
> {code}
>   PackedUnsignedLongs create(int count, long maxValue);
> {code}
> I think we should simply autogen the code (we can start from the
> autogen code in LUCENE-1410), or, if there is an good existing impl
> that has a compatible license that'd be great.
> I don't have time near-term to do this... so if anyone has the itch,
> please jump!

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