phantop/doukutsu-rs
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new rng

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Alula 2021-05-02 14:26:13 +02:00
parent ecabff27a8
commit 7844a4d26f
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1 changed files with 13 additions and 23 deletions
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36
src/rng.rs
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@ -1,5 +1,5 @@
use std::cell::Cell; use std::cell::Cell;
use std::ops::Range; use std::ops::{Range};
pub trait RNG { pub trait RNG {
fn next(&self) -> i32; fn next(&self) -> i32;
@ -10,45 +10,35 @@ pub trait RNG {
} }
/// Deterministic XorShift-based random number generator /// Deterministic XorShift-based random number generator
pub struct XorShift(Cell<(u64, u64, u64, u64)>); pub struct XorShift(Cell<u64>);
impl XorShift { impl XorShift {
pub fn new(seed: i32) -> Self { pub fn new(seed: i32) -> Self {
Self(Cell::new(( Self(Cell::new(seed as u64))
seed as u64,
(seed as u64).wrapping_add(0x9e3779b97f4a7c15),
(seed as u64).wrapping_add(0xbdd3944475a73cf0),
0
)))
} }
pub fn next_u64(&self) -> i32 { pub fn next_u64(&self) -> u64 {
let mut state = self.0.get(); let mut state = self.0.get();
let result = state.1.wrapping_mul(5).rotate_left(5).wrapping_mul(9);
let t = state.1 << 17;
state.2 ^= state.0; state ^= state >> 12;
state.3 ^= state.1; state ^= state << 25;
state.1 ^= state.2; state ^= state >> 27;
state.0 ^= state.3;
state.2 ^= t;
state.3 = state.3.rotate_left(45);
self.0.replace(state); self.0.replace(state);
result as i32
state.wrapping_mul(0x2545F4914F6CDD1Du64)
} }
#[inline] #[inline]
pub fn next_u32(&self) -> u32 { pub fn next_u32(&self) -> u32 {
self.next_u64() as u32 (self.next_u64() >> 32) as u32
} }
pub fn dump_state(&self) -> (u64, u64, u64, u64) { pub fn dump_state(&self) -> u64 {
self.0.get() self.0.get()
} }
pub fn load_state(&mut self, saved_state: (u64, u64, u64, u64)) { pub fn load_state(&mut self, saved_state: u64) {
self.0.replace(saved_state); self.0.replace(saved_state);
} }
} }
@ -56,7 +46,7 @@ impl XorShift {
impl RNG for XorShift { impl RNG for XorShift {
#[inline] #[inline]
fn next(&self) -> i32 { fn next(&self) -> i32 {
self.next_u64() as i32 self.next_u32() as i32
} }
} }