I recently found a super simple algorithm that appears to produce a number in the interval [0,N] with a branchless expression with a single multiplication in an extended number size. (Sorry I don't have a reference.)
Say you want to generate a number, G, in interval [0,N] where N<=UInt32Max. The algorithm is:
G = uint32( uint64(N)*uint64(rand.UInt32())>>32 )
Ps: it looks like your function is exclusive like [0,N) not [0,N] Also your function is described in this blog post https://www.pcg-random.org/posts/bounded-rands.html
Yes. There are many values of N that aren’t divisors of UInt32Max.
As the article says: “However, no algorithm can convert 2⁶³ equally likely values into n equally likely values unless 2⁶³ is a multiple of n: otherwise some outputs will necessarily happen more often than others. (As a simpler example, try converting 4 equally likely values into 3.)”
https://go.dev/play/p/IeJQEAclBCU
Edit: maybe this shows the bias better: https://go.dev/play/p/3eKJibIlF1a
No, but you can convert a RNG that emits 4 equally likely values into an RNG that emits 3 equally likely values. Just - anytime the RNG returns 4, try again.
Here's a fun puzzle / annoying interview question: You have a biased coin. You can flip it as often as you want, but heads and tails are not equally likely. Without figuring out the bias of the coin, how do you produce purely random bits?
My favorite is https://research.swtch.com/qart (see also: https://spinroot.com/pico/pjw.html)
The end of the post they mention that an encoding/json/v2 package is in the works: https://github.com/golang/go/discussions/63397
This is one of the reasons I love working in Go. I feel that the language maintainers understand that people using Go have more important work to do than update their code to whatever the new hotness is this month.
Basically the opposite of this: https://steve-yegge.medium.com/dear-google-cloud-your-deprec...
I think a lot of the benefit of putting stuff in the standard library is interoperability. It seems obvious but - having a string and list type in std means you can pass strings and lists between packages. I think a lot of standard stuff that acts as "glue" should be in std. For example, in nodejs the standard library includes HTTP request and response types because of how useful they are in their ecosystem.
Notably, unlike swift, rust doesn't have an "inlined string" type in std. There's a lot of crates that implement small strings, but most interfaces that need to pass an actual string buffer use std::String - and thats way less efficient. (Thankfully, &str is more common at interface boundaries). Rust also doesn't have much support for futures in std - which upsets a lot of people, because tokio ends up being included by a lot of programs.
Anyway, when it comes to crates like rand where interoperability isn't important, I think its fine to keep this stuff out of std. Code can evolve much more easily when it lives as a 3rd party library.
What happened to batteries-included support?
And even more ideally, as many v1 usages should be automatically fixed as possible by `go fix` or similar tools. Allowing this to all user packages would be a major improvement over the status quo.
We have plans to get there. https://github.com/golang/go/issues/32816