commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Alex D Herbert (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (RNG-72) Create a RandomSource.create benchmark
Date Fri, 01 Mar 2019 14:08:00 GMT

    [ https://issues.apache.org/jira/browse/RNG-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16781699#comment-16781699
] 

Alex D Herbert commented on RNG-72:
-----------------------------------

{quote}I think that synchronization is required within the "if (rng == null)" to avoid a race
condition.
{quote}

Yes. Good point.

I have in the past ignored this when using EnumMap to store stuff. Internally it uses a fixed
length array so you can add to it concurrently. But you risk breaking the state of the EnumMap
such as its known size. A race condition also creates multiple types of the item you are storing
of which only one will be permanent and the others will end up being discarded. Sometimes
this is OK.

However looking at the JDK source for creating a {{ThreadLocal<>}} it does some magic
with the thread table used to store the object which is most probably not OK.




> Create a RandomSource.create benchmark
> --------------------------------------
>
>                 Key: RNG-72
>                 URL: https://issues.apache.org/jira/browse/RNG-72
>             Project: Commons RNG
>          Issue Type: New Feature
>          Components: simple
>    Affects Versions: 1.3
>            Reporter: Alex D Herbert
>            Assignee: Alex D Herbert
>            Priority: Minor
>              Labels: performance-benchmark
>             Fix For: 1.3
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> The recommended method to construct a {{UniformRandomProvider}} is to use, e.g.:
> {code:java}
> import org.apache.commons.rng.UniformRandomProvider;
> import org.apache.commons.rng.simple.RandomSource;
> UniformRandomProvider rng = RandomSource.create(RandomSource.MWC_256);
> {code}
> The factory method knows the type of seed required for the constructor and generates
one as appropriate.
> This factory method could be made more efficient, in particular:
>  * Reducing synchronisation around the single source of random seed data
>  * Adding knowledge of the required seed size for arrays
>  * Changing internal data structures, e.g. {{Map<Class<?>, SeedConverter<?,?>>}}
can be changed to {{Map<SeedType, SeedConverter<?,?>>}} using an {{EnumMap}} if
a new enum {{SeedType}} was created for all the supported seeds (currently 4 types).
>  * Add a new interface to replace {{SeedConverter<?,?>.convert()}} with a {{.convert(int
outputArraySize)}} method to allow conversions to generate appropriately sized arrays. The
parameter can be ignored for non-array conversions but could optimise array conversions.
> This ticket is to add a JMH benchmark to compare the speed of construction of all the
providers using:
>  * Their native constructor
>  * {{RandomSource}} using the native seed of the correct size (calls a constructor using
reflection)
>  * {{RandomSource}} using a non native seed (requires seed conversion)
>  * {{RandomSource}} using no seed (requires seed generation)
> The report will be posted here. It could be added to the user guide for reference.
> This work is motivated by the new {{XorShiRo}} generators in version 1.3 that have a
native array seed size of 2, 4, or 8. The current {{RandomSource}} create method will generate
a fixed seed of length 128 for seeding.



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)

Mime
View raw message