feat!: require Rust 1.95, the minimum genoxide keeps from now on - #422
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…esult unchanged (#424) The follow-up to #402 and #422: the APIs that Rust 1.95 allows, plus the older ones #402 listed as "usable now". One topic per commit, each measured in instruction counts against its parent. Every seeded result is identical to the bit: `portable_runs`, the linalg fixed-bit tests, and all 223 examples against their `output.txt`. **Instruction counts, this branch against main** (valgrind, gungraun 0.19.4, Rust 1.99, one codegen unit). No benchmark gained. | Benchmark | Change | |---|---| | L-BFGS-B rounds, n = 1000 | −4.94% | | L-BFGS-B with forward differences | −1.11% | | gemm, n = 64 | −3.13% | | Cholesky, n = 200 | −0.81% | | CMA-ES sep-100 | −1.24% | | CMA-ES 10 | −0.29% | | DE generation | −0.12% | **Kept:** - **`core::hint::cold_path`** (1.95) on `ln`'s special cases, the source of the CMA-ES and DE gains, and on `exp`, a NaN violation, the Cholesky pivot, L-BFGS-B's projected gradient and Nelder-Mead's mirror. - **`array_windows`** (1.94) in Rosenbrock, Dixon-Price, Trid, Penalized 1 and 2, Schaffer F7, Kursawe, the gradients, the crowding distance, `nn` and more. The same float operations, in the same order. - **Slices cut to n** in `gemv` and in L-BFGS-B's O(n) loops, which removes their bounds checks. This is the −4.94%. - **`as_chunks_mut`** in gemm's A panel and in the Cholesky update's panel. - **`#[expect]` in place of `#[allow]`.** This removed the stale `dead_code` allows of `cholesky` and `triangular`, which L-BFGS-B uses now, and a stale `type_complexity`. - **For clarity, with counts unchanged:** `split_off`, `split_last_chunk` and `as_array` in checkpoints; `carrying_mul` in `below_u64`; `isqrt` in SPEA2 (the same k for every n up to 2^28); `is_multiple_of`. **Dropped, measured:** - **`cold_path` in `below_u64`:** tournament selection −2.9%, but DE +1.6%. - **`cold_path` in `Fitness::try_new`:** the fitness loop −8.5%, but the OneMax run +1.45%. - **`cold_path` on L-BFGS-B's skipped pair:** a small cost. - **`as_chunks_mut` for the Cholesky column tiles:** +0.87%. - **`f64::midpoint` in DE:** identical to the bit over 200M pairs and every class of f64, but DE +0.39%. **Not adopted:** `cfg_select!`. rustfmt doesn't format inside it, and the paired functions read no better wrapped in it.
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The decision in #402: the minimum supported Rust version moves from 1.88 to 1.95, and stays there.
Changes:
rust-version = "1.95"inCargo.tomlandpython/Cargo.toml.MSRV (1.95), ondtolnay/rust-toolchain@1.95.Checked:
cargo +1.95 check --all-targets --all-featurespasses.-D warnings, default and--all-featuresand on the Python crate, finds nothing new under the newrust-version.What 1.95 allows (#402), each to be adopted in its own PR, measured by the benchmarks and the bit-identical tests:
core::hint::cold_path(1.95) for rare branches in hot code;array_windows(1.94);as_array(1.93),cfg_select!(1.95) andcarrying_mul(1.91).Compiler improvements, LLVM 23 included, come with whatever toolchain users build with, whatever the minimum.
Who is affected: builds from source on a compiler older than 1.95, such as distribution packages up to Ubuntu 26.04's 1.93. rustup users and the Python wheels are unaffected. This is a breaking change, so the next release is a minor one.