joelkp / ranoise

Ranoise (random access noise) algorithms and PRNG tests and comparisons. Ranoise uses chaotic wavehaping to turn e.g. sawtooth-ish input values into white noise. Mirror of the repository on Codeberg.

I think the time has come to begin leaving GitHub behind. I'm more active on Codeberg, but I still check GitHub notifications.

My personal website has more on my projects and interests, and also points to some further places where you'll find me.

ranoise's Issues

splitmix32a info

Hello,

I'm possibly the one responsible for splitmix32a, or at least a lot of people seem to be using it from my post over at https://stackoverflow.com/a/52056161/815680.

I can't seem to find any source that I might've referenced prior to Aug 2018. There still might've been some unknown source that convinced me it was better than the supposed 'original', but can't remember anything for sure. I never tested it though, so I'm surprised that it's somehow better.

I actually had a slightly different version at first, before I quickly edited it the current constants.

uint32_t splitmix32(void) {
    uint32_t z = state += 0x3504f333;
    z ^= z >> 15; // 16 for murmur3
    z *= 0x85ebca6b;
    z ^= z >> 13;
    z *= 0xc2b2ae3d; // 0xc2b2ae35 for murmur3
    return z ^= z >> 16;
}

For some reason in this first version I used one constant from xxHash. No clue why. Of course the original is just a modified fmix fn from MurmurHash3.

I also chose an increment value related to Weyl sequences likely originating from here: http://marc-b-reynolds.github.io/math/2016/03/29/weyl_hash.html

I found a similar function that uses both of xxHash's constants in a similar function, also sharing that 0x3504f333 increment: https://www.thefiletree.com/espadrine/%E2%9A%92/random/weyl.html?app=html. Though this appears to be dated to 2020.

Feel free to close this issue, just sharing some info.