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use rand::{Rand, Rng, SeedableRng};
use std;
pub struct MersenneTwister {
state: [u32; 624],
index: usize,
}
impl MersenneTwister {
fn new_unseeded () -> MersenneTwister {
MersenneTwister { state: [0; 624], index: 0 }
}
}
impl Rng for MersenneTwister {
fn next_u32 (&mut self) -> u32 {
if self.index == 0 {
for i in 0..624 {
let y = (self.state[i] & 0x80000000)
.wrapping_add(self.state[(i + 1) % 624] & 0x7fffffff);
self.state[i] = self.state[(i + 397) % 624] ^ (y >> 1);
if (y % 2) != 0 {
self.state[i] = self.state[i] ^ 0x9908b0df;
}
}
}
let mut y = self.state[self.index];
y = y ^ (y >> 11);
y = y ^ ((y << 7) & 0x9d2c5680);
y = y ^ ((y << 15) & 0xefc60000);
y = y ^ (y >> 18);
self.index = (self.index + 1) % 624;
return y;
}
}
impl SeedableRng<u32> for MersenneTwister {
fn reseed (&mut self, seed: u32) {
self.state[0] = seed;
for i in 1..624 {
let prev = self.state[i - 1];
self.state[i] = 1812433253u32
.wrapping_mul(prev ^ (prev >> 30))
.wrapping_add(i as u32);
}
}
fn from_seed (seed: u32) -> MersenneTwister {
let mut mt = MersenneTwister::new_unseeded();
mt.reseed(seed);
mt
}
}
impl SeedableRng<([u32; 624], usize)> for MersenneTwister {
fn reseed (&mut self, seed: ([u32; 624], usize)) {
let (state, index) = seed;
for i in 0..624 {
self.state[i] = state[i];
}
self.index = index;
}
fn from_seed (seed: ([u32; 624], usize)) -> MersenneTwister {
let mut mt = MersenneTwister::new_unseeded();
mt.reseed(seed);
mt
}
}
impl Rand for MersenneTwister {
fn rand<R: Rng> (other: &mut R) -> MersenneTwister {
MersenneTwister::from_seed(other.next_u32())
}
}
impl Clone for MersenneTwister {
fn clone (&self) -> MersenneTwister {
MersenneTwister { state: self.state, index: self.index }
}
}
impl std::fmt::Debug for MersenneTwister {
fn fmt (&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
try!(write!(f, "MersenneTwister {{ "));
try!(std::fmt::Debug::fmt(&&self.state[..], f));
try!(write!(f, ", "));
try!(std::fmt::Debug::fmt(&self.index, f));
write!(f, " }}")
}
}
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