Switch to Wyrand

[SabrinaJewson]

Wyrand is faster than PCG and also passes all of the tests.

PCG benchmarks:

test shuffle_fastrand   ... bench:         405 ns/iter (+/- 9)
test u32_fastrand       ... bench:      13,779 ns/iter (+/- 657)
test u8_fastrand        ... bench:      13,771 ns/iter (+/- 696)

Wyrand benchmarks:

test shuffle_fastrand ... bench:         225 ns/iter (+/- 2)
test u32_fastrand     ... bench:      11,464 ns/iter (+/- 317)
test u8_fastrand      ... bench:      12,402 ns/iter (+/- 304)

Closes #19

[taiki-e]

It seems the current implementation of this PR vulnerable to some known bad seeds: wangyi-fudan/wyhash#100 ManDeJan/zig-wyhash#2 eldruin/wyhash-rs#6

[SabrinaJewson]

Does this apply to the RNG? The wyhash maintainer recently removed the _wyp default secret, but the wyrand implementation still uses it.

[taiki-e]

Thanks!

[taiki-e]

Published in 1.5.0

[flyingmutant]

I'd say it is a bit careless to say that "wyrand passes all of the tests", it certainly does not. Wyrand can only generate a subset of all u64 values (see wangyi-fudan/wyhash#16), and even if we consider that to not be a problem by itself, it leads to easily detectable biases. For example, the number of duplicates you get is consistently much higher than expected from random data: https://gist.github.com/flyingmutant/cb69e96872023f9f580868e746d1128a