Re[2]: The final optimized version of Dual-Pivot Quicksort (ver.19.1)

[Vladimir Yaroslavskiy]

Hi Brent,

see my comments inline:

>Четверг,  1 августа 2019, 9:23 +03:00 от Laurent Bourgès <bourges.laurent at gmail.com>:
>
>Hi Brent,
>
>Le jeu. 1 août 2019 à 02:32, Brent Christian < brent.christian at oracle.com > a écrit :
>>Thanks, Laurent.  I can sponsor this fix, get a RFR thread going for 
>>JDK-8226297, keep webrevs updated as the review progresses, etc.
Thank you for review!
>
>Excellent, I will let you and Vladimir work on this review. 
>
>FYI I have implemented DPQS (int[] ) sorting 2 arrays (values + indices) in the Marlin renderer. It could be generalized to any array type and having the index array is very important in many algorithms... 
>
>>
>>However I've uncovered an issue with the fix that should be resolved 
>>before proceeding.
>>
>>Specifically, the new Arrays.COMMON_PARALLELISM static constant causes 
>>exceptions at startup under some circumstances:
>>     * running with LANG=C on Linux[1]
>>     * setting a property value with non-Ascii characters on Mac[2]
>>
>>java.util.Arrays is used a fair bit for String handling 
>>(java.lang.StringCoding, java.langStringLatin1, etc).  The problem is 
>>that early in startup, depending on the locale/language setup and/or 
>>property settings, java.util.Arrays can be called during initialization 
>>of system properties.
>>
>>During Arrays.<clinit>, COMMON_PARALLELISM is setup with a call to 
>>ForkJoinPool.getCommonPoolParallelism().  ForkJoinPool<clinit> sets up 
>>some VarHandles, VarHandles<clinit> leads to 
>>MethodHandleStatics.<clinit>, which reads some system properties.  But 
>>we're still initializing the system properties - 'props' is null, so NPE.
>
>Chicken-egg problem. Maybe this field could be wrapped in a getter doing lazy resolution...
>>
>>I think Arrays.java needs to remove the COMMON_PARALLELISM constant, and 
>>go back to making calls to ForkJoinPool.getCommonPoolParallelism().
>
>I do not know why Vladimir changed that recently. Any good reason ?
>>
>>I can do the update and post an updated webrev (unless further 
>>discussion is needed).
Yes, please, remove COMMON_PARALLELISM constant and replace by call
ForkJoinPool.getCommonPoolParallelism(). in parallelSort() methods.

Please, go ahead and update webrev with corrected Arrays.java
>>
>PS: I can help on benchmarking as I developed a fair sort benchmark based on JMH:
>https://github.com/bourgesl/nearly-optimal-mergesort-code
>
>JMH test code:
>https://github.com/bourgesl/nearly-optimal-mergesort-code/tree/master/sort-bench/src/main/java/edu/sorting/bench
>I would be interested by improving the perf test code and possibly integrate it in OpenJDK JMH test suite... (later)
>
>Goodbye & good luck,
>Laurent
-- 
Vladimir Yaroslavskiy