v0.9.0

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Security and unsafe

• Policy: "rand is not a crypto library" (#​1514)
• Remove fork-protection from ReseedingRng and ThreadRng. Instead, it is recommended to call ThreadRng::reseed on fork. (#​1379)
• Use zerocopy to replace some unsafe code (#​1349, #​1393, #​1446, #​1502)

Dependencies

• Bump the MSRV to 1.63.0 (#​1207, #​1246, #​1269, #​1341, #​1416, #​1536); note that 1.60.0 may work for dependents when using --ignore-rust-version
• Update to rand_core v0.9.0 (#​1558)

Features

• Support std feature without getrandom or rand_chacha (#​1354)
• Enable feature small_rng by default (#​1455)
• Remove implicit feature rand_chacha; use std_rng instead. (#​1473)
• Rename feature serde1 to serde (#​1477)
• Rename feature getrandom to os_rng (#​1537)
• Add feature thread_rng (#​1547)

API changes: rand_core traits

• Add fn RngCore::read_adapter implementing std::io::Read (#​1267)
• Add trait CryptoBlockRng: BlockRngCore; make trait CryptoRng: RngCore (#​1273)
• Add traits TryRngCore, TryCryptoRng (#​1424, #​1499)
• Rename fn SeedableRng::from_rng -> try_from_rng and add infallible variant fn from_rng (#​1424)
• Rename fn SeedableRng::from_entropy -> from_os_rng and add fallible variant fn try_from_os_rng (#​1424)
• Add bounds Clone and AsRef to associated type SeedableRng::Seed (#​1491)

API changes: Rng trait and top-level fns

• Rename fn rand::thread_rng() to rand::rng() and remove from the prelude (#​1506)
• Remove fn rand::random() from the prelude (#​1506)
• Add top-level fns random_iter, random_range, random_bool, random_ratio, fill (#​1488)
• Re-introduce fn Rng::gen_iter as random_iter (#​1305, #​1500)
• Rename fn Rng::gen to random to avoid conflict with the new gen keyword in Rust 2024 (#​1438)
• Rename fns Rng::gen_range to random_range, gen_bool to random_bool, gen_ratio to random_ratio (#​1505)
• Annotate panicking methods with #[track_caller] (#​1442, #​1447)

API changes: RNGs

• Fix <SmallRng as SeedableRng>::Seed size to 256 bits (#​1455)
• Remove first parameter (rng) of ReseedingRng::new (#​1533)

API changes: Sequences

• Split trait SliceRandom into IndexedRandom, IndexedMutRandom, SliceRandom (#​1382)
• Add IndexedRandom::choose_multiple_array, index::sample_array (#​1453, #​1469)

API changes: Distributions: renames

• Rename module rand::distributions to rand::distr (#​1470)
• Rename distribution Standard to StandardUniform (#​1526)
• Move distr::Slice -> distr::slice::Choose, distr::EmptySlice -> distr::slice::Empty (#​1548)
• Rename trait distr::DistString -> distr::SampleString (#​1548)
• Rename distr::DistIter -> distr::Iter, distr::DistMap -> distr::Map (#​1548)

API changes: Distributions

• Relax Sized bound on Distribution<T> for &D (#​1278)
• Remove impl of Distribution<Option<T>> for StandardUniform (#​1526)
• Let distribution StandardUniform support all NonZero* types (#​1332)
• Fns {Uniform, UniformSampler}::{new, new_inclusive} return a Result (instead of potentially panicking) (#​1229)
• Distribution Uniform implements TryFrom instead of From for ranges (#​1229)
• Add UniformUsize (#​1487)
• Remove support for generating isize and usize values with StandardUniform, Uniform (except via UniformUsize) and Fill and usage as a WeightedAliasIndex weight (#​1487)
• Add impl DistString for distributions Slice<char> and Uniform<char> (#​1315)
• Add fn Slice::num_choices (#​1402)
• Add fn p() for distribution Bernoulli to access probability (#​1481)

API changes: Weighted distributions

• Add pub module rand::distr::weighted, moving WeightedIndex there (#​1548)
• Add trait weighted::Weight, allowing WeightedIndex to trap overflow (#​1353)
• Add fns weight, weights, total_weight to distribution WeightedIndex (#​1420)
• Rename enum WeightedError to weighted::Error, revising variants (#​1382) and mark as #[non_exhaustive] (#​1480)

API changes: SIMD

• Switch to std::simd, expand SIMD & docs (#​1239)

Reproducibility-breaking changes

• Make ReseedingRng::reseed discard remaining data from the last block generated (#​1379)
• Change fn SmallRng::seed_from_u64 implementation (#​1203)
• Allow UniformFloat::new samples and UniformFloat::sample_single to yield high (#​1462)
• Fix portability of distribution Slice (#​1469)
• Make Uniform for usize portable via UniformUsize (#​1487)
• Fix IndexdRandom::choose_multiple_weighted for very small seeds and optimize for large input length / low memory (#​1530)

Reproducibility-breaking optimisations

• Optimize fn sample_floyd, affecting output of rand::seq::index::sample and rand::seq::SliceRandom::choose_multiple (#​1277)
• New, faster algorithms for IteratorRandom::choose and choose_stable (#​1268)
• New, faster algorithms for SliceRandom::shuffle and partial_shuffle (#​1272)
• Optimize distribution Uniform: use Canon's method (single sampling) / Lemire's method (distribution sampling) for faster sampling (breaks value stability; #​1287)
• Optimize fn sample_single_inclusive for floats (+~20% perf) (#​1289)

Other optimisations

• Improve SmallRng initialization performance (#​1482)
• Optimise SIMD widening multiply (#​1247)

Other

• Add Cargo.lock.msrv file (#​1275)
• Reformat with rustfmt and enforce (#​1448)
• Apply Clippy suggestions and enforce (#​1448, #​1474)
• Move all benchmarks to new benches crate (#​1329, #​1439) and migrate to Criterion (#​1490)

Documentation

• Improve ThreadRng related docs (#​1257)
• Docs: enable experimental --generate-link-to-definition feature (#​1327)
• Better doc of crate features, use doc_auto_cfg (#​1411, #​1450)