On: RaptorQ and performance optimization in Rust

[littlestymaar]

Does it still provide the DoS protection SipHash offered, or does that mean that Rust is moving from secure-by-default to fastest-by-default when it comes to HashMap ? If so it's kind of a big philosophical switch.

[rapsey → littlestymaar]

Hashbrown is not about the hashing algorithm. It uses fx hash which is pretty commonly used in Rust. I imagine they will still keep SipHash

[littlestymaar → rapsey]

OK thanks. But that would mean the performance gain would not be as dramatic I guess ?

[Manishearth → littlestymaar]

It's still pretty major, because SIMD, but not as dramatic

https://github.com/Amanieu/hashbrown#performance

Note that the hashbrown crate uses FxHash by default, so the second table is the fair comparison. When ported to the stdlib it will likely be changed to have SipHash as the default.

For the standard hashmap, replacing SipHash with FxHash gets you a 4x perf boost. Replacing the standard hashmap with hashbrown gets you a 2x perf boost (when you're using FxHash, there are no numbers here for when you're using SipHash but I suspect it will still be significant, if smaller)

[littlestymaar → Manishearth]

Thanks a lot for the clarification!