[
https://issues.apache.org/jira/browse/LUCENE-2719?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Uwe Schindler updated LUCENE-2719:
----------------------------------
Attachment: LUCENE-2719.patch
Modified all sorts to use >>>1 instead /2 (have no real opinion about that).
bq. Yep - Solr also has it's own version of quicksort - PrimUtils.sort() to
deal with sorting indexes (an int[]) instead of objects (parallel array
sorting).
According to java.util.Arrays javadoc: The sorting algorithm is a tuned
quicksort, adapted from Jon L. Bentley and M. Douglas McIlroy's "Engineering a
Sort Function", Software-Practice and Experience, Vol. 23(11) P. 1249-1265
(November 1993). This algorithm offers n*log(n) performance on many data sets
that cause other quicksorts to degrade to quadratic performance.
If I change to SorterTemplate, we will degrade to good old quicksort. We could
also upgrade SorterTemplate to use this algo, but I am not sure if thats easy
because SorterTemplate only allows swap(index, index) and compare(index,
index). But we cannot retrieve e.g. the pivot value. This was also one problem
in porting BytesRefHash's quicksort, as it used the value of the pivot (this is
why there is an additional check below the commented out assert in the current
patch's algo).
> Re-add SorterTemplate and use it to provide fast ArraySorting and replace
> BytesRefHash sorting
> ----------------------------------------------------------------------------------------------
>
> Key: LUCENE-2719
> URL: https://issues.apache.org/jira/browse/LUCENE-2719
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: 3.1
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Fix For: 3.1, 4.0
>
> Attachments: LUCENE-2719.patch, LUCENE-2719.patch, LUCENE-2719.patch,
> LUCENE-2719.patch
>
>
> This patch adds back an optimized and rewritten SorterTemplate back to Lucene
> (removed after release of 3.0). It is of use for several components:
> - Automaton: Automaton needs to sort States and other things. Using
> Arrays.sort() is slow, because it clones internally to ensure stable search.
> This component is much faster. This patch adds Arrays.sort() replacements in
> ArrayUtil that work with natural order or using a Comparator<?>. You can
> choose between quickSort and mergeSort.
> - BytesRefHash uses another QuickSort algorithm without insertionSort for
> very short ord arrays. This class uses SorterTemplate to provide the same
> with insertionSort fallback in a very elegant way. Ideally this class can be
> used everywhere, where the sort algorithm needs to be separated from the
> underlying data and you can implement a swap() and compare() function (that
> get slot numbers instead of real values). This also applies to Solr (Yonik?).
> SorterTemplate provides quickSort and mergeSort algorithms. Internally for
> short arrays, it automatically chooses insertionSort (like JDK's Arrays). The
> quickSort algorith was copied modified from old BytesRefHash. This new class
> only shares MergeSort with the original CGLIB SorterTemplate, which is no
> longer maintained.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
