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In rust you can use either model. Not really. Of course you can copy immutable data upon update, but persistent data structures (large shared state between dat

by szemet 9y ago

In rust you can use either model. Not really. Of course you can copy immutable data upon update, but persistent data structures (large shared state between data versions)[1] are hard to write without GC... [1] https://en.m.wikipedia.org/wiki/Persistent_data_structure https://en.m.wikipedia.org/wiki/Persistent_data_structure

littlestymaar 9y ago
If you don't have cycles, ref counting can work (it's a kind of GC after all), but it indeed comes with a big performance overhead compared to a modern GC.
smaddox 9y ago
Reference counting [1] and atomic reference counting [2] are supported within Rust, and are sufficient for any persistent data structure without cycles. There's also a prototype crate for a mark and sweep GC [3], which would likely work for anything else. Writing such data structures using these features might be a bit more tedious than writing them in a GC language, but I suspect the increased explicitness provides a worthwhile tradeoff. See the crossbeam library [4] for some examples of lockless concurrent data structures implemented in Rust. [1] https://doc.rust-lang.org/std/rc/struct.Rc.html https://doc.rust-lang.org/std/rc/struct.Rc.html [2] https://doc.rust-lang.org/std/sync/struct.Arc.html https://doc.rust-lang.org/std/sync/struct.Arc.html [3] https://manishearth.github.io/blog/2016/08/18/gc-support-in-rust-api-design/ https://manishearth.github.io/blog/2016/08/18/gc-support-in-... [4] https://github.com/crossbeam-rs/crossbeam https://github.com/crossbeam-rs/crossbeam
- littlestymaar 9y ago
  As an alternative GC in Rust, you also have Josephine[1], which uses the SpiderMonkey[2] GC. It's cumbersome to use though[3] and should probably not be used outside of Servo. [1]: https://github.com/asajeffrey/josephine https://github.com/asajeffrey/josephine [2]: mozilla's JS VM [3]: this is how you call a doubly linked list managed by the JS GC https://github.com/asajeffrey/josephine/blob/master/examples/dbllist/main.rs https://github.com/asajeffrey/josephine/blob/master/examples...

by szemet 9y ago

littlestymaar 9y ago

If you don't have cycles, ref counting can work (it's a kind of GC after all), but it indeed comes with a big performance overhead compared to a modern GC.

smaddox 9y ago

Reference counting [1] and atomic reference counting [2] are supported within Rust, and are sufficient for any persistent data structure without cycles. There's also a prototype crate for a mark and sweep GC [3], which would likely work for anything else. Writing such data structures using these features might be a bit more tedious than writing them in a GC language, but I suspect the increased explicitness provides a worthwhile tradeoff. See the crossbeam library [4] for some examples of lockless concurrent data structures implemented in Rust. [1] https://doc.rust-lang.org/std/rc/struct.Rc.html https://doc.rust-lang.org/std/rc/struct.Rc.html [2] https://doc.rust-lang.org/std/sync/struct.Arc.html https://doc.rust-lang.org/std/sync/struct.Arc.html [3] https://manishearth.github.io/blog/2016/08/18/gc-support-in-rust-api-design/ https://manishearth.github.io/blog/2016/08/18/gc-support-in-... [4] https://github.com/crossbeam-rs/crossbeam https://github.com/crossbeam-rs/crossbeam

littlestymaar 9y ago
As an alternative GC in Rust, you also have Josephine[1], which uses the SpiderMonkey[2] GC. It's cumbersome to use though[3] and should probably not be used outside of Servo. [1]: https://github.com/asajeffrey/josephine https://github.com/asajeffrey/josephine [2]: mozilla's JS VM [3]: this is how you call a doubly linked list managed by the JS GC https://github.com/asajeffrey/josephine/blob/master/examples/dbllist/main.rs https://github.com/asajeffrey/josephine/blob/master/examples...