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https://issues.apache.org/jira/browse/LUCY-49?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Marvin Humphrey updated LUCY-49:
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Attachment: SortUtils.c
SortUtils.bp
> Context-aware mergesort and quicksort
> -------------------------------------
>
> Key: LUCY-49
> URL: https://issues.apache.org/jira/browse/LUCY-49
> Project: Lucy
> Issue Type: Improvement
> Components: Core
> Reporter: Marvin Humphrey
> Assignee: Marvin Humphrey
> Priority: Blocker
> Attachments: SortUtils.bp, SortUtils.c
>
>
> The only sort routine you can count on the system providing is qsort. Some
> systems provide a qsort_r which takes a context argument in addition to the
> items being compared, but not all, and the function signature differs on the
> systems that do provide it (with context being either the first or the last
> argument to the comparison function).
> Lucy::Util::SortUtils provides a context-aware quicksort and a context-aware
> mergesort. The mergesort also exposes merge routines which are optimized for
> use by an external sorter, as they minimize copying.
> The quicksort implementation guards against the classic quicksort worst-case
> behavior with careful pivot selection. One popular quicksort optimization is
> still TODO: using insertion sort for array slices of 10 or fewer elements.
> Implementing that optimization may be worthwhile, as this quicksort will
> probably be used for the first level of token-sorting at index time.
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