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Comment by SomeCallMeTim | Hacker News Reader

Actually, in my experience using the default random implementation in games:

* It's not fast enough. * It has patterns that can be seen if you are using it to, for instance, generate 2d noise.

So for games you'd typically use, say, the Mersenne Twister [1], which is faster (amortized) and is distributed evenly across 623 dimensions. [2]

It's not cryptographic, but it's far better for games. If you're not going to have a crypto default random, better to at least have a really good and really fast one.

[1] https://en.wikipedia.org/wiki/Mersenne_twister

[2] http://www.math.sci.hiroshima-u.ac.jp/m-mat/MT/ARTICLES/mt.p...

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Mersenne Twister is the MD5 of random number generators: it's neither secure nor fast (and unlikely md5 not space-efficient, or simple to implement either). You can have something that has better randomness, runs several times faster, uses less space and has a much more compact and simple implementation.

So given that Mersenne Twister sucks in pretty much every possible way other than having a catchy name, likely the sole source of its continued popularity, its probably not a good choice for replacing some "default" random number generator with something better.

> You can have something that has better randomness, runs several times faster, uses less space and has a much more compact and simple implementation.

Could you share at least one example of such a generator?

Most of these aspects are trivial to improve on, but having "better randomness" on top is quite the bar.

The PCG class of PRNGs are very good, and have a zillion tunable versions to suit every need.

https://www.pcg-random.org/index.html

MCG 128 from http://www.pcg-random.org/posts/on-vignas-pcg-critique.html or xoshiro256plus from http://prng.di.unimi.it/xoshiro256plus.c

https://en.wikipedia.org/wiki/Mersenne_Twister#Alternatives

https://nullprogram.com/blog/2017/09/21/

I don't think better randomness than MT is as high a bar as you make it out to be, both links above also briefly mention statistical shortcomings of MT.

Doesn't FreeBSD use Mersenne Twister as its CSRNG?

No, FreeBSD uses Fortuna https://en.wikipedia.org/wiki/Fortuna_(PRNG)

Mersenne Twister is not secure, and it isn’t a very good RNG even for insecure uses.

Thanks! I don't know why I thought they used it.

Patterned random numbers become a feature in some games, even if an unintentional one.

I used to be able to play about a dozen Pac-Man levels knowing exactly where every ghost was going to go and every bonus that was going to appear. And I wasn’t a very good player.

Pac-Man would have been a less fun game for many people if it used crypto grade random.

Pac-Man ghosts did not moved all that much randomly. Each ghost had special follow up strategy. You likely learned their movement patterns without realizing it.

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