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From "Alex D Herbert (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (RNG-72) Create a RandomSource.create benchmark
Date Fri, 01 Mar 2019 13:02:00 GMT

    [ https://issues.apache.org/jira/browse/RNG-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16781647#comment-16781647
] 

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

{quote}Hence, how about providing a convenience class that would store one {{ThreadLocal<UniformRandomProvider>}} per
RNG implementation
{quote}

Something like this (totally untested) idea:

{code:java}
public final class ThreadLocalRandomSource {

    private static EnumMap<RandomSource, ThreadLocal<UniformRandomProvider>> sources
=
        new EnumMap<RandomSource,
                    ThreadLocal<UniformRandomProvider>>(RandomSource.class);

    private static class ThreadLocalRNG extends ThreadLocal<UniformRandomProvider> {
        final RandomSource source;

        ThreadLocalRNG(RandomSource source) {
            this.source = source;
        }

        @Override
        protected UniformRandomProvider initialValue() {
            return RandomSource.create(source);
        }
    }

    public static UniformRandomProvider current(RandomSource source) {
        ThreadLocal<UniformRandomProvider> rng = sources.get(source);
        if (rng == null) {
            rng = new ThreadLocalRNG(source);
            sources.put(source, rng);
        }
        return rng.get();
    }
}
{code}


> 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.



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