The new optimized version of Dual-Pivot Quicksort

[Laurent Bourgès]

Hi,

One more thing: if you have any advice on my code, datasets, or algorithmic
approach, please give me your feedback/comments.

Here is the Marlin MergeSort:
http://hg.openjdk.java.net/jdk/jdk/file/190b77982361/src/java.desktop/share/classes/sun/java2d/marlin/MergeSort.java

Laurent

Le ven. 9 nov. 2018 à 08:44, Laurent Bourgès <bourges.laurent at gmail.com> a
écrit :

> Hi,
>
> I am currently testing many sort algorithms to improve the Marlin renderer
> (AA 2D shape rasterizer), I integrated since OpenJDK9 and am still
> improving for OpenJDK12 .
>
> I created my MergeSort (top down, check for sorted parts, array / buffer
> swap to minimize moves, isort on small sub arrays) that sort 2 int[]:
> crossing + edge indices.
>  It is critical as edge crossings are sorted at every scanline, data are
> almost sorted/reversed, not really random.
>
> 3 questions:
> - why is this patch dormant ? I checked in openjdk12 repo and your changes
> were not integrated.
> - I need a sort() method that works with 2 arrays: data + indices (pointer
> like). Such sorted indices are useful to use for lookups c[idx[k]] or to
> perform other array permutations...
> Would you agree adding such new sort(a[], low, high, indices)
> - Marlin uses a ThreadLocal context to avoid any allocation. JDK sort()
> impl do not accept parameters to give any buffer[] and avoid allocations.
> Would you agree adding such optional parameters (like workbase[]) ?
>
> I will experiment adapting the DualPivotQuickSort in Marlin renderer and
> perform array sort race & rendering benchmarks.
>
> Cheers,
> Laurent
>
> Le ven. 19 janv. 2018 à 14:38, Vladimir Yaroslavskiy <vlv.spb.ru at mail.ru>
> a écrit :
>
>> Hi team,
>>
>> In Sept 2009 Josh Bloch, Jon Bentley and I introduced new sorting
>> algorithm, Dual-Pivot Quicksort, for primitives in JDK 7 and later
>> I suggested several improvements of Dual-Pivot Quicksort, which
>> were integrated into JDK 8.
>>
>> Now I have more optimized and faster version of Dual-Pivot Quicksort.
>> I have been working on it for the last 5 years. Please, find the
>> summary of changes below and sources / diff at webrev [1].
>>
>> All tests and benchmarking were run on the most recent build of JDK 10,
>> jdk-10-ea+39. The new version shows the better performance on different
>> inputs and guarantees n*log(n) on any data.
>>
>> The new implementation of Dual-Pivot Quicksort is 'all-in-one' version:
>> it contains one code for both parallel and sequential sorting algorithms.
>>
>> Suggested version is 10-20% faster on random data, 1.5-4 times faster
>> on nearly structured arrays, 1.5-2 times faster on period inputs.
>>
>> Parallel Dual-Pivot Quicksort is 1.5-3 times faster than current
>> algorithm based on merge sort.
>>
>> Benchmarking on the test suite, suggested by Jon Bentley, shows the
>> boost of performance in 1.4 times. This test suite contains several
>> types of inputs, such as random data, nearly structured arrays, data
>> with period and so on. Also there are several modifications of inputs
>> and parameters which are used in data building. We run sorting on all
>> combinations to compare two algorithms.
>>
>> Please let me know if you have any questions / comments.
>>
>> Summary of changes:
>>
>> DualPivotQuicksort class
>> ------------------------
>> * Pivots are chosen with another step, the 1-st and 5-th candidates
>>    are taken as pivots instead of 2-nd and 4-th.
>> * Splitting into parts is related to the golden ratio
>> * Pivot candidates are sorted by combination of 5-element
>>    network sorting + insertion sort
>> * New backwards partitioning is simpler and more efficient
>> * Quicksort tuning parameters were updated
>> * Merging sort is invoked on each iteration from Quicksort
>> * Additional steps for float/double were fully rewritten
>> * Heap sort is invoked on the leftmost part
>> * Heap sort is used as a guard against quadratic time
>> * Parallel sorting is based on Dual-Pivot Quicksort
>>    instead of merge sort
>>
>> SortingAlgorithms class
>> -----------------------
>> * Merging sort and pair insertion sort were moved from
>>    DualPivotQuicksort class
>> * Pair insertion sort was simplified and optimized
>> * New nano insertion sort was introduced for tiny arrays
>> * Merging sort was fully rewritten
>> * Optimized merging partitioning is used
>> * Merging parameters were updated
>> * Merging of runs was fully rewritten
>> * Fast version of heap sort was introduced
>> * Parallel merging sort was also provided
>>
>> Sorting / ParallelSorting classes
>> ---------------------------------
>> * New test cases were added
>> * Sources of these classes were unified
>>
>> Arrays class
>> ------------
>> * Calls of Dual-Pivot Quicksort were updated
>> * Parallel sorting of primitives was switched to parallel
>>    Dual-Pivot Quicksort
>> * Javadoc was modified
>>
>> ArraysParallelSortHelpers class
>> -------------------------------
>> * Old implementation of parallel sorting for primitives was removed
>> * Javadoc was updated
>>
>> Thank you,
>> Vladimir
>>
>> --------------------------------------------------------------------
>> [1] http://cr.openjdk.java.net/~alanb/DualPivotSortUpdate/webrev.01/
>> --------------------------------------------------------------------
>>
>