For strings of any notable length, Fx Hash outperforms FNV. Rustc also
moved to this hash function and noticed performance
improvements. Fortunately, as was accounted for in the design, this was a
trivial switch.
Here are some benchmarks to back up that claim:
test hash_set::fnv::with_all_new_1000 ... bench: 133,096 ns/iter (+/- 1,430)
test hash_set::fnv::with_all_new_1000_with_capacity ... bench: 82,591 ns/iter (+/- 592)
test hash_set::fnv::with_all_new_rc_str_1000_baseline ... bench: 162,073 ns/iter (+/- 1,277)
test hash_set::fnv::with_one_new_1000 ... bench: 37,334 ns/iter (+/- 256)
test hash_set::fnv::with_one_new_rc_str_1000_baseline ... bench: 18,263 ns/iter (+/- 261)
test hash_set::fx::with_all_new_1000 ... bench: 85,217 ns/iter (+/- 1,111)
test hash_set::fx::with_all_new_1000_with_capacity ... bench: 59,383 ns/iter (+/- 752)
test hash_set::fx::with_all_new_rc_str_1000_baseline ... bench: 98,802 ns/iter (+/- 1,117)
test hash_set::fx::with_one_new_1000 ... bench: 42,484 ns/iter (+/- 1,239)
test hash_set::fx::with_one_new_rc_str_1000_baseline ... bench: 15,000 ns/iter (+/- 233)
test hash_set::with_all_new_1000 ... bench: 137,645 ns/iter (+/- 1,186)
test hash_set::with_all_new_rc_str_1000_baseline ... bench: 163,129 ns/iter (+/- 1,725)
test hash_set::with_one_new_1000 ... bench: 59,051 ns/iter (+/- 1,202)
test hash_set::with_one_new_rc_str_1000_baseline ... bench: 37,986 ns/iter (+/- 771)
This is missing two key things that I'll add shortly: a HashMap-based one
for use in the ASG for node mapping, and an entry-based system for
manipulations.
This has been a nice start for exploring various aspects of Rust
development, as well as conventions that I'd like to implement. In
particular:
- Robust documentation intended to guide people through learning the
necessary material about the compiler, as well as related work to
rationalize design decisions;
- Benchmarks;
- TDD;
- And just getting used to Rust in general.
I've beat this one to death, so I'll commit this and make smaller changes
going forward to show how easily it can evolve.
(This module was originally named `intern` but this commit and those that
follow rewrote it to `sym`.)
Mike Gerwitz