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Accommodate arith-overflow in rand and std::rand.

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Regarding the `rand` changes: It is unfortunate that Wrapping(T) does
not support the `+=` operator.  We may want to try to fix that before
1.0 to make porting code like this palatable.

Regarding `std::rand`, just arith-overflow in first example from
`std::rand::random()` doc.
This commit is contained in:
Felix S. Klock II 2015-02-20 00:10:08 +01:00
parent 7c8edabac8
commit 6189e99c86
4 changed files with 41 additions and 38 deletions
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11
src/librand/chacha.rs
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@ -12,6 +12,7 @@
use core::prelude::*;
use core::num::Int;
use core::num::wrapping::WrappingOps;
use {Rng, SeedableRng, Rand};
const KEY_WORDS : uint = 8; // 8 words for the 256-bit key
@ -43,10 +44,10 @@ static EMPTY: ChaChaRng = ChaChaRng {
macro_rules! quarter_round{
($a: expr, $b: expr, $c: expr, $d: expr) => {{
$a += $b; $d ^= $a; $d = $d.rotate_left(16);
$c += $d; $b ^= $c; $b = $b.rotate_left(12);
$a += $b; $d ^= $a; $d = $d.rotate_left( 8);
$c += $d; $b ^= $c; $b = $b.rotate_left( 7);
$a = $a.wrapping_add($b); $d = $d ^ $a; $d = $d.rotate_left(16);
$c = $c.wrapping_add($d); $b = $b ^ $c; $b = $b.rotate_left(12);
$a = $a.wrapping_add($b); $d = $d ^ $a; $d = $d.rotate_left( 8);
$c = $c.wrapping_add($d); $b = $b ^ $c; $b = $b.rotate_left( 7);
}}
}
@ -74,7 +75,7 @@ fn core(output: &mut [u32; STATE_WORDS], input: &[u32; STATE_WORDS]) {
}
for i in 0..STATE_WORDS {
output[i] += input[i];
output[i] = output[i].wrapping_add(input[i]);
}
}

2
src/librand/distributions/range.rs
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@ -123,7 +123,7 @@ macro_rules! integer_impl {
// be uniformly distributed)
if v < r.accept_zone as $unsigned {
// and return it, with some adjustments
return r.low + (v % r.range as $unsigned) as $ty;
return r.low.wrapping_add((v % r.range as $unsigned) as $ty);
}
}
}

62
src/librand/isaac.rs
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@ -13,6 +13,7 @@
use core::prelude::*;
use core::slice;
use core::iter::{range_step, repeat};
use core::num::wrapping::Wrapping;
use {Rng, SeedableRng, Rand};
@ -60,7 +61,7 @@ impl IsaacRng {
/// of `rsl` as a seed, otherwise construct one algorithmically (not
/// randomly).
fn init(&mut self, use_rsl: bool) {
let mut a = 0x9e3779b9;
let mut a = Wrapping(0x9e3779b9);
let mut b = a;
let mut c = a;
let mut d = a;
@ -71,14 +72,14 @@ impl IsaacRng {
macro_rules! mix {
() => {{
a^=b<<11; d+=a; b+=c;
b^=c>>2; e+=b; c+=d;
c^=d<<8; f+=c; d+=e;
d^=e>>16; g+=d; e+=f;
e^=f<<10; h+=e; f+=g;
f^=g>>4; a+=f; g+=h;
g^=h<<8; b+=g; h+=a;
h^=a>>9; c+=h; a+=b;
a=a^(b<<11); d=d+a; b=b+c;
b=b^(c>>2); e=e+b; c=c+d;
c=c^(d<<8); f=f+c; d=d+e;
d=d^(e>>16); g=g+d; e=e+f;
e=e^(f<<10); h=h+e; f=f+g;
f=f^(g>>4); a=a+f; g=g+h;
g=g^(h<<8); b=b+g; h=h+a;
h=h^(a>>9); c=c+h; a=a+b;
}}
}
@ -90,15 +91,15 @@ impl IsaacRng {
macro_rules! memloop {
($arr:expr) => {{
for i in range_step(0, RAND_SIZE as uint, 8) {
a+=$arr[i ]; b+=$arr[i+1];
c+=$arr[i+2]; d+=$arr[i+3];
e+=$arr[i+4]; f+=$arr[i+5];
g+=$arr[i+6]; h+=$arr[i+7];
a=a+Wrapping($arr[i ]); b=b+Wrapping($arr[i+1]);
c=c+Wrapping($arr[i+2]); d=d+Wrapping($arr[i+3]);
e=e+Wrapping($arr[i+4]); f=f+Wrapping($arr[i+5]);
g=g+Wrapping($arr[i+6]); h=h+Wrapping($arr[i+7]);
mix!();
self.mem[i ]=a; self.mem[i+1]=b;
self.mem[i+2]=c; self.mem[i+3]=d;
self.mem[i+4]=e; self.mem[i+5]=f;
self.mem[i+6]=g; self.mem[i+7]=h;
self.mem[i ]=a.0; self.mem[i+1]=b.0;
self.mem[i+2]=c.0; self.mem[i+3]=d.0;
self.mem[i+4]=e.0; self.mem[i+5]=f.0;
self.mem[i+6]=g.0; self.mem[i+7]=h.0;
}
}}
}
@ -108,10 +109,10 @@ impl IsaacRng {
} else {
for i in range_step(0, RAND_SIZE as uint, 8) {
mix!();
self.mem[i ]=a; self.mem[i+1]=b;
self.mem[i+2]=c; self.mem[i+3]=d;
self.mem[i+4]=e; self.mem[i+5]=f;
self.mem[i+6]=g; self.mem[i+7]=h;
self.mem[i ]=a.0; self.mem[i+1]=b.0;
self.mem[i+2]=c.0; self.mem[i+3]=d.0;
self.mem[i+4]=e.0; self.mem[i+5]=f.0;
self.mem[i+6]=g.0; self.mem[i+7]=h.0;
}
}
@ -130,7 +131,8 @@ impl IsaacRng {
static MIDPOINT: uint = (RAND_SIZE / 2) as uint;
macro_rules! ind {
($x:expr) => ( self.mem[(($x >> 2) as uint & ((RAND_SIZE - 1) as uint))] )
($x:expr) => (Wrapping( self.mem[(($x >> 2) as uint &
((RAND_SIZE - 1) as uint))] ))
}
let r = [(0, MIDPOINT), (MIDPOINT, 0)];
@ -142,11 +144,11 @@ impl IsaacRng {
let mix = a << $shift as uint;
let x = self.mem[base + mr_offset];
a = (a ^ mix) + self.mem[base + m2_offset];
let y = ind!(x) + a + b;
self.mem[base + mr_offset] = y;
a = (Wrapping(a ^ mix) + Wrapping(self.mem[base + m2_offset])).0;
let y = ind!(x) + Wrapping(a) + Wrapping(b);
self.mem[base + mr_offset] = y.0;
b = ind!(y >> RAND_SIZE_LEN as uint) + x;
b = (ind!(y.0 >> RAND_SIZE_LEN as uint) + Wrapping(x)).0;
self.rsl[base + mr_offset] = b;
}}
}
@ -157,11 +159,11 @@ impl IsaacRng {
let mix = a >> $shift as uint;
let x = self.mem[base + mr_offset];
a = (a ^ mix) + self.mem[base + m2_offset];
let y = ind!(x) + a + b;
self.mem[base + mr_offset] = y;
a = (Wrapping(a ^ mix) + Wrapping(self.mem[base + m2_offset])).0;
let y = ind!(x) + Wrapping(a) + Wrapping(b);
self.mem[base + mr_offset] = y.0;
b = ind!(y >> RAND_SIZE_LEN as uint) + x;
b = (ind!(y.0 >> RAND_SIZE_LEN as uint) + Wrapping(x)).0;
self.rsl[base + mr_offset] = b;
}}
}

4
src/libstd/rand/mod.rs
View File

@ -386,8 +386,8 @@ impl Rng for ThreadRng {
/// ```
/// use std::rand;
///
/// let x = rand::random();
/// println!("{}", 2u8 * x);
/// let x: u8 = rand::random();
/// println!("{}", 2 * x as u16);
///
/// let y = rand::random::<f64>();
/// println!("{}", y);