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Posted to dev@lucene.apache.org by "Adrien Grand (JIRA)" <ji...@apache.org> on 2016/03/11 17:34:00 UTC
[jira] [Issue Comment Deleted] (LUCENE-7097) Can we increase the
stack depth before Introsorter switches to heapsort?
[ https://issues.apache.org/jira/browse/LUCENE-7097?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Adrien Grand updated LUCENE-7097:
---------------------------------
Comment: was deleted
(was: If we change it to add this 2x factor then maybe we should also take the floor of the log2 instead of the ceil to be on par with the paper.)
> Can we increase the stack depth before Introsorter switches to heapsort?
> ------------------------------------------------------------------------
>
> Key: LUCENE-7097
> URL: https://issues.apache.org/jira/browse/LUCENE-7097
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Fix For: trunk, 6.1
>
>
> Introsort is a "safe" quicksort: it uses quicksort but detects when an adversary is at work and cuts over to heapsort at that point.
> The description at https://en.wikipedia.org/wiki/Introsort shows the cutover as 2X log_2(N) but our impl ({{IntroSorter}}) currently uses just log_2.
> So I tested using 2X log_2 instead, and I see a decent (~5.6%, from 98.2 sec to 92.7 sec) speedup in the time for offline sorter to sort when doing the force merge of 6.1 LatLonPoints from the London UK benchmark.
> Is there any reason not to switch? I know this means 2X the stack required, but since this is log_2 space that seems fine?
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