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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4098) Efficient bulk operations for packed integer arrays
Date Fri, 01 Jun 2012 18:25:23 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4098?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287581#comment-13287581
] 

Adrien Grand commented on LUCENE-4098:
--------------------------------------

The bulk get and set are not guaranteed to return/set exactly len longs (so that they can
stay at a block boundary to make the subsequent reads/writes faster). So I think
{{code}}
int got = packed1.get(start, buffer, offset, len);
assertTrue(got <= len);
int sot = packed2.set(start, buffer, offset, len);
assertTrue(sot <= len);
{{code}}
should be replaced with
{{code}}
int got = packed1.get(start, buffer, offset, len);
assertTrue(got <= len);
int sot = packed2.set(start, buffer, offset, got);
assertTrue(sot <= len);
{{code}}
                
> Efficient bulk operations for packed integer arrays
> ---------------------------------------------------
>
>                 Key: LUCENE-4098
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4098
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/other
>            Reporter: Adrien Grand
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 4.1
>
>         Attachments: LUCENE-4098.patch, LUCENE-4098.patch
>
>
> There are some places in Lucene code that {iterate over,set} ranges of values of a packed
integer array. Because bit-packing implementations (Packed*) tend be slower than direct implementations,
this can take a lot of time.
> For example, under some scenarii, GrowableWriter can take most of its (averaged) {{set}}
time in resizing operations.
> However, some bit-packing schemes, such as the one that is used by {{Packed64SingleBlock*}},
allow to implement efficient bulk operations such as get/set/fill. Implementing these bulk
operations in {{PackedInts.{Reader,Mutable}}} and using them across other components instead
of their single-value counterpart could help improve performance.

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