diff --git a/Cargo.toml b/Cargo.toml index f9cc4350..49cf64ed 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -5,6 +5,7 @@ members = [ "rand_xorshift", "rand_xoshiro", "rand_hc", + "rand_sfc" ] exclude = [ "benches", diff --git a/rand_sfc/Cargo.toml b/rand_sfc/Cargo.toml new file mode 100644 index 00000000..656db456 --- /dev/null +++ b/rand_sfc/Cargo.toml @@ -0,0 +1,14 @@ +[package] +name = "rand_sfc" +version = "0.1.0" +edition = "2021" +rust-version = "1.63" +keywords = ["random", "rng", "sfc"] +categories = ["algorithms", "no-std"] + +[features] +serde1 = ["serde"] + +[dependencies] +rand_core = { version = "0.9.0" } +serde = { version = "1.0.118", default-features = false, features = ["derive"], optional = true } \ No newline at end of file diff --git a/rand_sfc/LICENSE-APACHE b/rand_sfc/LICENSE-APACHE new file mode 100644 index 00000000..494ad3bf --- /dev/null +++ b/rand_sfc/LICENSE-APACHE @@ -0,0 +1,176 @@ + Apache License + Version 2.0, January 2004 + https://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. 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IN NO EVENT +SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY +CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR +IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. diff --git a/rand_sfc/src/lib.rs b/rand_sfc/src/lib.rs new file mode 100644 index 00000000..96d2c5a7 --- /dev/null +++ b/rand_sfc/src/lib.rs @@ -0,0 +1,39 @@ +// Copyright 2025 Developers of the Rand project. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +//! This crate implements the sfc (Small Fast Counting) family of pseudorandom +//! number generators designed by Chris Doty-Humphrey, author of the [PractRand] +//! pseudorandom number generator testing suite. The generators have a small +//! state, good statistical quality, and high performance. Like most generators +//! intended for non-cryptographic use, they can be [predicted]. They also have +//! a variable period, but the counter present in the state provides a fixed +//! lower bound and [most states] are on the longest cycle. +//! +//! This crate provides: +//! - [`Sfc64`]: 64 bit output, seed space 192 bits, worst-case period 2^64, +//! and expected period ~2^255. +//! - [`Sfc32`]: 32 bit output, seed space 96 bits, worst-case period 2^32, +//! and expected period ~2^127. +//! +//! The implementations provided are derived from PractRand. +//! +//! [PractRand]: https://pracrand.sourceforge.net/ +//! [predicted]: https://github.com/michaelni/randomtests/blob/main/sfc64-breach.c +//! [most states]: https://www.pcg-random.org/posts/random-invertible-mapping-statistics.html + +#![forbid(unsafe_code)] +#![deny(missing_docs)] +#![deny(missing_debug_implementations)] +#![no_std] + +mod sfc32; +mod sfc64; + +pub use rand_core; +pub use sfc32::Sfc32; +pub use sfc64::Sfc64; \ No newline at end of file diff --git a/rand_sfc/src/sfc32.rs b/rand_sfc/src/sfc32.rs new file mode 100644 index 00000000..a5b6f635 --- /dev/null +++ b/rand_sfc/src/sfc32.rs @@ -0,0 +1,124 @@ +// Copyright 2025 Developers of the Rand project. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use rand_core::le::read_u32_into; +use rand_core::{RngCore, SeedableRng}; +use rand_core::impls::{fill_bytes_via_next, next_u64_via_u32}; + +#[allow(missing_copy_implementations)] +#[derive(Debug, Clone, PartialEq, Eq)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +/// An sfc32 random number generator. +/// +/// Good performance and statistical quality, but not cryptographically secure +/// and has a large difference between its worst-case and maximum period. +/// +/// This implementation is derived ultimately from +/// [`the PractRand RNG test suite`](https://pracrand.sourceforge.net/) by +/// Chris Doty-Humphrey. +pub struct Sfc32 { + a: u32, + b: u32, + c: u32, + weyl: u32, +} + +const BARREL_SHIFT: u32 = 21; +const RSHIFT: u32 = 9; +const LSHIFT: u32 = 3; +// WEYL_INC is always 1 in the PractRand implementation, but some other +// implementations use it to provide a stream facility. This is not yet +// implemented here, though. +const WEYL_INC: u32 = 1; + +impl RngCore for Sfc32 { + #[inline] + fn next_u32(&mut self) -> u32 { + let old_b = self.b; + let old_c = self.c; + let old_weyl = self.weyl; + + let result = self.a.wrapping_add(old_b).wrapping_add(old_weyl); + self.a = old_b ^ (old_b >> RSHIFT); + self.b = old_c.wrapping_add(old_c << LSHIFT); + self.c = result.wrapping_add(old_c.rotate_left(BARREL_SHIFT)); + self.weyl = old_weyl.wrapping_add(WEYL_INC); + result + } + + #[inline] + fn next_u64(&mut self) -> u64 { + next_u64_via_u32(self) + } + + #[inline] + fn fill_bytes(&mut self, dest: &mut [u8]) { + fill_bytes_via_next(self, dest); + } +} + +// PracRand uses different mixing step counts for different types of seeds. +// Here, just use one of the larger values always. +const SEED_MIXING_STEPS: u32 = 16; + +impl SeedableRng for Sfc32 { + type Seed = [u8; 12]; + + /// Create a new `Sfc32`. + fn from_seed(seed: [u8; 12]) -> Sfc32 { + let mut s = [0; 3]; + read_u32_into(&seed, &mut s); + + let mut rng = Sfc32 { + a: s[0], + b: s[1], + c: s[2], + weyl: WEYL_INC + }; + + for _ in 0..SEED_MIXING_STEPS { + rng.next_u32(); + } + + rng + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn reference() { + // These values were produced with the reference implementation: + // https://pracrand.sourceforge.net/ + let mut rng = Sfc32::from_seed([0, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0]); + let expected: [u32; 16] = [ + 0xA87DBC7E, + 0x1787178C, + 0x4C7B7234, + 0xC65DADE2, + 0x2C692349, + 0xF52C2153, + 0xDF098072, + 0x9D49B03C, + 0x9562381A, + 0xC9B41738, + 0x64B75E54, + 0x36CE9B32, + 0xF106947E, + 0x0AFC726B, + 0x549BBC87, + 0xD19A7B3E + ]; + + for &e in &expected { + assert_eq!(rng.next_u32(), e); + } + } +} \ No newline at end of file diff --git a/rand_sfc/src/sfc64.rs b/rand_sfc/src/sfc64.rs new file mode 100644 index 00000000..c48b2fb1 --- /dev/null +++ b/rand_sfc/src/sfc64.rs @@ -0,0 +1,131 @@ +// Copyright 2025 Developers of the Rand project. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use rand_core::le::read_u64_into; +use rand_core::{RngCore, SeedableRng}; +use rand_core::impls::fill_bytes_via_next; + +#[allow(missing_copy_implementations)] +#[derive(Debug, Clone, PartialEq, Eq)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +/// An sfc64 random number generator. +/// +/// Good performance and statistical quality, but not cryptographically secure +/// and has a large difference between its worst-case and maximum period. +/// sfc64 has a longer period than sfc32 and should perform as well or better +/// on 64-bit processors, though Chris Doty-Humphrey believes its statistical +/// properties are similar to sfc32. +/// +/// This implementation is derived ultimately from +/// [`the PractRand RNG test suite`](https://pracrand.sourceforge.net/) by +/// Chris Doty-Humphrey. +pub struct Sfc64 { + a: u64, + b: u64, + c: u64, + weyl: u64, +} + +const BARREL_SHIFT: u32 = 24; +const RSHIFT: u32 = 11; +const LSHIFT: u32 = 3; +// WEYL_INC is always 1 in the PractRand implementation, but some other +// implementations use it to provide a stream facility. This is not yet +// implemented here, though. +const WEYL_INC: u64 = 1; + +impl RngCore for Sfc64 { + #[inline] + fn next_u32(&mut self) -> u32 { + (self.next_u64() >> 32) as u32 + } + + #[inline] + fn next_u64(&mut self) -> u64 { + let old_b = self.b; + let old_c = self.c; + let old_weyl = self.weyl; + + let result = self.a.wrapping_add(old_b).wrapping_add(old_weyl); + self.a = old_b ^ (old_b >> RSHIFT); + self.b = old_c.wrapping_add(old_c << LSHIFT); + self.c = result.wrapping_add(old_c.rotate_left(BARREL_SHIFT)); + self.weyl = self.weyl.wrapping_add(WEYL_INC); + result + } + + #[inline] + fn fill_bytes(&mut self, dest: &mut [u8]) { + fill_bytes_via_next(self, dest); + } +} + +// PracRand uses different mixing step counts for different types of seeds. +// Here, just use one of the larger values always. +const SEED_MIXING_STEPS: u32 = 18; + +impl SeedableRng for Sfc64 { + type Seed = [u8; 24]; + + /// Create a new `Sfc64`. + fn from_seed(seed: [u8; 24]) -> Sfc64 { + let mut s = [0; 3]; + read_u64_into(&seed, &mut s); + + let mut rng = Sfc64 { + a: s[0], + b: s[1], + c: s[2], + weyl: WEYL_INC + }; + + for _ in 0..SEED_MIXING_STEPS { + rng.next_u64(); + } + rng + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn reference() { + // These values were produced with the reference implementation: + // https://pracrand.sourceforge.net/ + let mut rng = Sfc64::from_seed([ + 1, 0, 0, 0, 0, 0, 0, 0, + 1, 0, 0, 0, 0, 0, 0, 0, + 1, 0, 0, 0, 0, 0, 0, 0, + ]); + + let expected: [u64; 16] = [ + 0xAD6FDC729FEEF3C1, + 0x2A20433D733F77D5, + 0x0310E21369647420, + 0x331A176BC71DCABC, + 0x53118F35C2494D94, + 0xA3A99DE7E77E16BF, + 0xA7B1B70A3E59A1FF, + 0x8E1127B28667EB3C, + 0x3FC589DC124CF6E8, + 0x81E0EAAACEB81D81, + 0x79F534652D262DF6, + 0x87F70C8214E186C5, + 0x67AF9C007B825917, + 0x5134AEC9998D8629, + 0x205AA24994068634, + 0x1C762918DBA3E139 + ]; + + for &e in &expected { + assert_eq!(rng.next_u64(), e); + } + } +} \ No newline at end of file