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Diffstat (limited to 'rand/rand_isaac/src/isaac64.rs')
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1 files changed, 481 insertions, 0 deletions
diff --git a/rand/rand_isaac/src/isaac64.rs b/rand/rand_isaac/src/isaac64.rs new file mode 100644 index 0000000..2712762 --- /dev/null +++ b/rand/rand_isaac/src/isaac64.rs @@ -0,0 +1,481 @@ +// Copyright 2018 Developers of the Rand project. +// Copyright 2013-2018 The Rust Project Developers. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +//! The ISAAC-64 random number generator. + +use core::{fmt, slice}; +use core::num::Wrapping as w; +use rand_core::{RngCore, SeedableRng, Error, le}; +use rand_core::block::{BlockRngCore, BlockRng64}; +use isaac_array::IsaacArray; + +#[allow(non_camel_case_types)] +type w64 = w<u64>; + +const RAND_SIZE_LEN: usize = 8; +const RAND_SIZE: usize = 1 << RAND_SIZE_LEN; + +/// A random number generator that uses ISAAC-64, the 64-bit variant of the +/// ISAAC algorithm. +/// +/// ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are +/// the principal bitwise operations employed. It is the most advanced of a +/// series of array based random number generator designed by Robert Jenkins +/// in 1996[^1]. +/// +/// ISAAC-64 is mostly similar to ISAAC. Because it operates on 64-bit integers +/// instead of 32-bit, it uses twice as much memory to hold its state and +/// results. Also it uses different constants for shifts and indirect indexing, +/// optimized to give good results for 64bit arithmetic. +/// +/// ISAAC-64 is notably fast and produces excellent quality random numbers for +/// non-cryptographic applications. +/// +/// In spite of being designed with cryptographic security in mind, ISAAC hasn't +/// been stringently cryptanalyzed and thus cryptographers do not not +/// consensually trust it to be secure. When looking for a secure RNG, prefer +/// [`Hc128Rng`] instead, which, like ISAAC, is an array-based RNG and one of +/// the stream-ciphers selected the by eSTREAM contest. +/// +/// ## Overview of the ISAAC-64 algorithm: +/// (in pseudo-code) +/// +/// ```text +/// Input: a, b, c, s[256] // state +/// Output: r[256] // results +/// +/// mix(a,i) = !(a ^ a << 21) if i = 0 mod 4 +/// a ^ a >> 5 if i = 1 mod 4 +/// a ^ a << 12 if i = 2 mod 4 +/// a ^ a >> 33 if i = 3 mod 4 +/// +/// c = c + 1 +/// b = b + c +/// +/// for i in 0..256 { +/// x = s_[i] +/// a = mix(a,i) + s[i+128 mod 256] +/// y = a + b + s[x>>3 mod 256] +/// s[i] = y +/// b = x + s[y>>11 mod 256] +/// r[i] = b +/// } +/// ``` +/// +/// This implementation uses [`BlockRng64`] to implement the [`RngCore`] methods. +/// +/// See for more information the documentation of [`IsaacRng`]. +/// +/// [^1]: Bob Jenkins, [*ISAAC and RC4*]( +/// http://burtleburtle.net/bob/rand/isaac.html) +/// +/// [`IsaacRng`]: ../isaac/struct.IsaacRng.html +/// [`Hc128Rng`]: ../../rand_hc/struct.Hc128Rng.html +/// [`BlockRng64`]: ../../rand_core/block/struct.BlockRng64.html +/// [`RngCore`]: ../../rand_core/trait.RngCore.html +#[derive(Clone, Debug)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +pub struct Isaac64Rng(BlockRng64<Isaac64Core>); + +impl RngCore for Isaac64Rng { + #[inline(always)] + fn next_u32(&mut self) -> u32 { + self.0.next_u32() + } + + #[inline(always)] + fn next_u64(&mut self) -> u64 { + self.0.next_u64() + } + + fn fill_bytes(&mut self, dest: &mut [u8]) { + self.0.fill_bytes(dest) + } + + fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { + self.0.try_fill_bytes(dest) + } +} + +impl SeedableRng for Isaac64Rng { + type Seed = <Isaac64Core as SeedableRng>::Seed; + + fn from_seed(seed: Self::Seed) -> Self { + Isaac64Rng(BlockRng64::<Isaac64Core>::from_seed(seed)) + } + + /// Create an ISAAC random number generator using an `u64` as seed. + /// If `seed == 0` this will produce the same stream of random numbers as + /// the reference implementation when used unseeded. + fn seed_from_u64(seed: u64) -> Self { + Isaac64Rng(BlockRng64::<Isaac64Core>::seed_from_u64(seed)) + } + + fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> { + BlockRng64::<Isaac64Core>::from_rng(rng).map(|rng| Isaac64Rng(rng)) + } +} + +impl Isaac64Rng { + /// Create an ISAAC-64 random number generator using an `u64` as seed. + /// If `seed == 0` this will produce the same stream of random numbers as + /// the reference implementation when used unseeded. + #[deprecated(since="0.6.0", note="use SeedableRng::seed_from_u64 instead")] + pub fn new_from_u64(seed: u64) -> Self { + Self::seed_from_u64(seed) + } +} + +/// The core of `Isaac64Rng`, used with `BlockRng`. +#[derive(Clone)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +pub struct Isaac64Core { + #[cfg_attr(feature="serde1",serde(with="super::isaac_array::isaac_array_serde"))] + mem: [w64; RAND_SIZE], + a: w64, + b: w64, + c: w64, +} + +// Custom Debug implementation that does not expose the internal state +impl fmt::Debug for Isaac64Core { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "Isaac64Core {{}}") + } +} + +impl BlockRngCore for Isaac64Core { + type Item = u64; + type Results = IsaacArray<Self::Item>; + + /// Refills the output buffer, `results`. See also the pseudocode desciption + /// of the algorithm in the [`Isaac64Rng`] documentation. + /// + /// Optimisations used (similar to the reference implementation): + /// + /// - The loop is unrolled 4 times, once for every constant of mix(). + /// - The contents of the main loop are moved to a function `rngstep`, to + /// reduce code duplication. + /// - We use local variables for a and b, which helps with optimisations. + /// - We split the main loop in two, one that operates over 0..128 and one + /// over 128..256. This way we can optimise out the addition and modulus + /// from `s[i+128 mod 256]`. + /// - We maintain one index `i` and add `m` or `m2` as base (m2 for the + /// `s[i+128 mod 256]`), relying on the optimizer to turn it into pointer + /// arithmetic. + /// - We fill `results` backwards. The reference implementation reads values + /// from `results` in reverse. We read them in the normal direction, to + /// make `fill_bytes` a memcopy. To maintain compatibility we fill in + /// reverse. + /// + /// [`Isaac64Rng`]: struct.Isaac64Rng.html + fn generate(&mut self, results: &mut IsaacArray<Self::Item>) { + self.c += w(1); + // abbreviations + let mut a = self.a; + let mut b = self.b + self.c; + const MIDPOINT: usize = RAND_SIZE / 2; + + #[inline] + fn ind(mem:&[w64; RAND_SIZE], v: w64, amount: usize) -> w64 { + let index = (v >> amount).0 as usize % RAND_SIZE; + mem[index] + } + + #[inline] + fn rngstep(mem: &mut [w64; RAND_SIZE], + results: &mut [u64; RAND_SIZE], + mix: w64, + a: &mut w64, + b: &mut w64, + base: usize, + m: usize, + m2: usize) { + let x = mem[base + m]; + *a = mix + mem[base + m2]; + let y = *a + *b + ind(&mem, x, 3); + mem[base + m] = y; + *b = x + ind(&mem, y, 3 + RAND_SIZE_LEN); + results[RAND_SIZE - 1 - base - m] = (*b).0; + } + + let mut m = 0; + let mut m2 = MIDPOINT; + for i in (0..MIDPOINT/4).map(|i| i * 4) { + rngstep(&mut self.mem, results, !(a ^ (a << 21)), &mut a, &mut b, i + 0, m, m2); + rngstep(&mut self.mem, results, a ^ (a >> 5 ), &mut a, &mut b, i + 1, m, m2); + rngstep(&mut self.mem, results, a ^ (a << 12), &mut a, &mut b, i + 2, m, m2); + rngstep(&mut self.mem, results, a ^ (a >> 33), &mut a, &mut b, i + 3, m, m2); + } + + m = MIDPOINT; + m2 = 0; + for i in (0..MIDPOINT/4).map(|i| i * 4) { + rngstep(&mut self.mem, results, !(a ^ (a << 21)), &mut a, &mut b, i + 0, m, m2); + rngstep(&mut self.mem, results, a ^ (a >> 5 ), &mut a, &mut b, i + 1, m, m2); + rngstep(&mut self.mem, results, a ^ (a << 12), &mut a, &mut b, i + 2, m, m2); + rngstep(&mut self.mem, results, a ^ (a >> 33), &mut a, &mut b, i + 3, m, m2); + } + + self.a = a; + self.b = b; + } +} + +impl Isaac64Core { + /// Create a new ISAAC-64 random number generator. + fn init(mut mem: [w64; RAND_SIZE], rounds: u32) -> Self { + fn mix(a: &mut w64, b: &mut w64, c: &mut w64, d: &mut w64, + e: &mut w64, f: &mut w64, g: &mut w64, h: &mut w64) { + *a -= *e; *f ^= *h >> 9; *h += *a; + *b -= *f; *g ^= *a << 9; *a += *b; + *c -= *g; *h ^= *b >> 23; *b += *c; + *d -= *h; *a ^= *c << 15; *c += *d; + *e -= *a; *b ^= *d >> 14; *d += *e; + *f -= *b; *c ^= *e << 20; *e += *f; + *g -= *c; *d ^= *f >> 17; *f += *g; + *h -= *d; *e ^= *g << 14; *g += *h; + } + + // These numbers are the result of initializing a...h with the + // fractional part of the golden ratio in binary (0x9e3779b97f4a7c13) + // and applying mix() 4 times. + let mut a = w(0x647c4677a2884b7c); + let mut b = w(0xb9f8b322c73ac862); + let mut c = w(0x8c0ea5053d4712a0); + let mut d = w(0xb29b2e824a595524); + let mut e = w(0x82f053db8355e0ce); + let mut f = w(0x48fe4a0fa5a09315); + let mut g = w(0xae985bf2cbfc89ed); + let mut h = w(0x98f5704f6c44c0ab); + + // Normally this should do two passes, to make all of the seed effect + // all of `mem` + for _ in 0..rounds { + for i in (0..RAND_SIZE/8).map(|i| i * 8) { + a += mem[i ]; b += mem[i+1]; + c += mem[i+2]; d += mem[i+3]; + e += mem[i+4]; f += mem[i+5]; + g += mem[i+6]; h += mem[i+7]; + mix(&mut a, &mut b, &mut c, &mut d, + &mut e, &mut f, &mut g, &mut h); + mem[i ] = a; mem[i+1] = b; + mem[i+2] = c; mem[i+3] = d; + mem[i+4] = e; mem[i+5] = f; + mem[i+6] = g; mem[i+7] = h; + } + } + + Self { mem, a: w(0), b: w(0), c: w(0) } + } + + /// Create an ISAAC-64 random number generator using an `u64` as seed. + /// If `seed == 0` this will produce the same stream of random numbers as + /// the reference implementation when used unseeded. + #[deprecated(since="0.6.0", note="use SeedableRng::seed_from_u64 instead")] + pub fn new_from_u64(seed: u64) -> Self { + Self::seed_from_u64(seed) + } +} + +impl SeedableRng for Isaac64Core { + type Seed = [u8; 32]; + + fn from_seed(seed: Self::Seed) -> Self { + let mut seed_u64 = [0u64; 4]; + le::read_u64_into(&seed, &mut seed_u64); + // Convert the seed to `Wrapping<u64>` and zero-extend to `RAND_SIZE`. + let mut seed_extended = [w(0); RAND_SIZE]; + for (x, y) in seed_extended.iter_mut().zip(seed_u64.iter()) { + *x = w(*y); + } + Self::init(seed_extended, 2) + } + + fn seed_from_u64(seed: u64) -> Self { + let mut key = [w(0); RAND_SIZE]; + key[0] = w(seed); + // Initialize with only one pass. + // A second pass does not improve the quality here, because all of the + // seed was already available in the first round. + // Not doing the second pass has the small advantage that if + // `seed == 0` this method produces exactly the same state as the + // reference implementation when used unseeded. + Self::init(key, 1) + } + + fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> { + // Custom `from_rng` implementation that fills a seed with the same size + // as the entire state. + let mut seed = [w(0u64); RAND_SIZE]; + unsafe { + let ptr = seed.as_mut_ptr() as *mut u8; + let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE * 8); + rng.try_fill_bytes(slice)?; + } + for i in seed.iter_mut() { + *i = w(i.0.to_le()); + } + + Ok(Self::init(seed, 2)) + } +} + +#[cfg(test)] +mod test { + use rand_core::{RngCore, SeedableRng}; + use super::Isaac64Rng; + + #[test] + fn test_isaac64_construction() { + // Test that various construction techniques produce a working RNG. + let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0, + 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; + let mut rng1 = Isaac64Rng::from_seed(seed); + assert_eq!(rng1.next_u64(), 14964555543728284049); + + let mut rng2 = Isaac64Rng::from_rng(rng1).unwrap(); + assert_eq!(rng2.next_u64(), 919595328260451758); + } + + #[test] + fn test_isaac64_true_values_64() { + let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0, + 200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0]; + let mut rng1 = Isaac64Rng::from_seed(seed); + let mut results = [0u64; 10]; + for i in results.iter_mut() { *i = rng1.next_u64(); } + let expected = [ + 15071495833797886820, 7720185633435529318, + 10836773366498097981, 5414053799617603544, + 12890513357046278984, 17001051845652595546, + 9240803642279356310, 12558996012687158051, + 14673053937227185542, 1677046725350116783]; + assert_eq!(results, expected); + + let seed = [57,48,0,0, 0,0,0,0, 50,9,1,0, 0,0,0,0, + 49,212,0,0, 0,0,0,0, 148,38,0,0, 0,0,0,0]; + let mut rng2 = Isaac64Rng::from_seed(seed); + // skip forward to the 10000th number + for _ in 0..10000 { rng2.next_u64(); } + + for i in results.iter_mut() { *i = rng2.next_u64(); } + let expected = [ + 18143823860592706164, 8491801882678285927, 2699425367717515619, + 17196852593171130876, 2606123525235546165, 15790932315217671084, + 596345674630742204, 9947027391921273664, 11788097613744130851, + 10391409374914919106]; + assert_eq!(results, expected); + } + + #[test] + fn test_isaac64_true_values_32() { + let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0, + 200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0]; + let mut rng = Isaac64Rng::from_seed(seed); + let mut results = [0u32; 12]; + for i in results.iter_mut() { *i = rng.next_u32(); } + // Subset of above values, as an LE u32 sequence + let expected = [ + 3477963620, 3509106075, + 687845478, 1797495790, + 227048253, 2523132918, + 4044335064, 1260557630, + 4079741768, 3001306521, + 69157722, 3958365844]; + assert_eq!(results, expected); + } + + #[test] + fn test_isaac64_true_values_mixed() { + let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0, + 200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0]; + let mut rng = Isaac64Rng::from_seed(seed); + // Test alternating between `next_u64` and `next_u32` works as expected. + // Values are the same as `test_isaac64_true_values` and + // `test_isaac64_true_values_32`. + assert_eq!(rng.next_u64(), 15071495833797886820); + assert_eq!(rng.next_u32(), 687845478); + assert_eq!(rng.next_u32(), 1797495790); + assert_eq!(rng.next_u64(), 10836773366498097981); + assert_eq!(rng.next_u32(), 4044335064); + // Skip one u32 + assert_eq!(rng.next_u64(), 12890513357046278984); + assert_eq!(rng.next_u32(), 69157722); + } + + #[test] + fn test_isaac64_true_bytes() { + let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0, + 200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0]; + let mut rng = Isaac64Rng::from_seed(seed); + let mut results = [0u8; 32]; + rng.fill_bytes(&mut results); + // Same as first values in test_isaac64_true_values as bytes in LE order + let expected = [100, 131, 77, 207, 155, 181, 40, 209, + 102, 176, 255, 40, 238, 155, 35, 107, + 61, 123, 136, 13, 246, 243, 99, 150, + 216, 167, 15, 241, 62, 149, 34, 75]; + assert_eq!(results, expected); + } + + #[test] + fn test_isaac64_new_uninitialized() { + // Compare the results from initializing `IsaacRng` with + // `seed_from_u64(0)`, to make sure it is the same as the reference + // implementation when used uninitialized. + // Note: We only test the first 16 integers, not the full 256 of the + // first block. + let mut rng = Isaac64Rng::seed_from_u64(0); + let mut results = [0u64; 16]; + for i in results.iter_mut() { *i = rng.next_u64(); } + let expected: [u64; 16] = [ + 0xF67DFBA498E4937C, 0x84A5066A9204F380, 0xFEE34BD5F5514DBB, + 0x4D1664739B8F80D6, 0x8607459AB52A14AA, 0x0E78BC5A98529E49, + 0xFE5332822AD13777, 0x556C27525E33D01A, 0x08643CA615F3149F, + 0xD0771FAF3CB04714, 0x30E86F68A37B008D, 0x3074EBC0488A3ADF, + 0x270645EA7A2790BC, 0x5601A0A8D3763C6A, 0x2F83071F53F325DD, + 0xB9090F3D42D2D2EA]; + assert_eq!(results, expected); + } + + #[test] + fn test_isaac64_clone() { + let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0, + 200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0]; + let mut rng1 = Isaac64Rng::from_seed(seed); + let mut rng2 = rng1.clone(); + for _ in 0..16 { + assert_eq!(rng1.next_u64(), rng2.next_u64()); + } + } + + #[test] + #[cfg(feature="serde1")] + fn test_isaac64_serde() { + use bincode; + use std::io::{BufWriter, BufReader}; + + let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0, + 57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; + let mut rng = Isaac64Rng::from_seed(seed); + + let buf: Vec<u8> = Vec::new(); + let mut buf = BufWriter::new(buf); + bincode::serialize_into(&mut buf, &rng).expect("Could not serialize"); + + let buf = buf.into_inner().unwrap(); + let mut read = BufReader::new(&buf[..]); + let mut deserialized: Isaac64Rng = bincode::deserialize_from(&mut read).expect("Could not deserialize"); + + for _ in 0..300 { // more than the 256 buffered results + assert_eq!(rng.next_u64(), deserialized.next_u64()); + } + } +} |