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Make ArenaVec a Vec over a std Allocator - #332
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kevaundray wants to merge 1 commit into
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The `Allocator` trait, `Vec<T, A>` and `Box<T, A>` are stable from Rust 1.100 (rust-lang/rust#156882). `zk_alloc::Arena` is a zero-sized `Allocator` over `raw_alloc`/`raw_dealloc`, which already tell arena from system memory by address, and `ArenaVec<T>` is `Vec<T, Arena>`. The hand-written vector is gone and every `Vec` method works on an `ArenaVec`. - `Vec`'s constructors belong to the global allocator, so `new`, `with_capacity`, `from_slice`, `filled`, `zeroed`, `uninitialized` and `from_iter` move to an `ArenaVecExt` trait. `collect()`, `Default` and `mem::take` are unavailable for the same reason; four call sites use `from_iter` and `mem::replace` instead. - `primitives::multilinear::Shrink` only let the folds take either vector type. It is deleted and the folds are generic over `A: Allocator`, calling `truncate` (not `Vec::shrink_to`, which shrinks capacity). - An allocator's methods must never unwind. The address space was reserved lazily inside the first allocation behind an `assert!`; `enable_arena` now reserves it. - `clippy::uninit_vec` now sees two deliberate uninitialized vectors it could not see through the old type; each gets an `#[expect]` with its reason. Requires Rust 1.100 (nightly until it ships); stable 1.97 rejects `allocator_api`. Measured on x86-64 (32 threads), same nightly for both builds, alternating runs, proving time: fibonacci --n 2000000: base 1.864 s, 1.883 s; new 1.889 s, 1.923 s leanxmss --n 400: base 3.247, 3.275, 3.152 (±7.2%) s; new 3.284, 3.244, 3.248 s No difference beyond run-to-run noise; peak memory within 0.3%.
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CI fails because its not using nightly-1.100 |
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closing |
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This is an experiment to see what it would look like to adopt thw new allocator API that was standardised in nightly rust 1.100.
This is not meant to be merged, we can just wait for it to go onto stable.