[jira] [Commented] (LUCENE-7261) Speed up LSBRadixSorter

["Yonik Seeley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-7261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15262186#comment-15262186 ] 

Yonik Seeley commented on LUCENE-7261:
--------------------------------------

+1

As an aside, I was looking at this stuff a while ago and had decided on trying an MSB sort first (before you added LSB).
- can be in-place
- since all buckets are sorted relative to each other, can delegate to a different sorting algorithm when buckets become small



> Speed up LSBRadixSorter
> -----------------------
>
>                 Key: LUCENE-7261
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7261
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Adrien Grand
>            Assignee: Adrien Grand
>            Priority: Minor
>         Attachments: LUCENE-7261.patch
>
>
> Currently it always does 4 passes over the data (one per byte, since ints have 4 bytes). However, most of the time, we know {{maxDoc}}, so we can use this information to do fewer passes when they are not necessary. For instance, if maxDoc is less than or equal to 2^24, we only need 3 passes, and if maxDoc is less than or equals to 2^16, we only need two passes.



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