RFR: 8275821: Optimize random number generators developed in JDK-8248862 using Math.unsignedMultiplyHigh() [v4]

[Vamsi Parasa]

On Thu, 2 Dec 2021 20:43:56 GMT, Vamsi Parasa <duke at openjdk.java.net> wrote:

>> This change optimizes random number generators using Math.unsignedMultiplyHigh()
>
> Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add seeds for the random generators to eliminate run-to-run variance

The following speedups were observed for the JMH benchmarks. L128X128MixRandom shows 8% improvement, L128x256MixRandom shows 6% improvement and L128X1024MixRandom shows 14% improvement. (Another micro workload shows 10% improvement for both L128X128MixRandom and L128x256MixRandom while L128X1024MixRandom shows 25% improvement in performance.)

@JimLaskey Could you please review this PR which optimizes three of the Pseudo-Random Number Generators you implemented in https://bugs.openjdk.java.net/browse/JDK-8248862 ?

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PR: https://git.openjdk.java.net/jdk/pull/6206