mirror of
https://github.com/ziglang/zig.git
synced 2024-11-27 15:42:49 +00:00
d29871977f
We already have a LICENSE file that covers the Zig Standard Library. We no longer need to remind everyone that the license is MIT in every single file. Previously this was introduced to clarify the situation for a fork of Zig that made Zig's LICENSE file harder to find, and replaced it with their own license that required annual payments to their company. However that fork now appears to be dead. So there is no need to reinforce the copyright notice in every single file.
120 lines
2.6 KiB
Zig
120 lines
2.6 KiB
Zig
//! PCG32 - http://www.pcg-random.org/
|
|
//!
|
|
//! PRNG
|
|
|
|
const std = @import("std");
|
|
const Random = std.rand.Random;
|
|
const Pcg = @This();
|
|
|
|
const default_multiplier = 6364136223846793005;
|
|
|
|
random: Random,
|
|
|
|
s: u64,
|
|
i: u64,
|
|
|
|
pub fn init(init_s: u64) Pcg {
|
|
var pcg = Pcg{
|
|
.random = Random{ .fillFn = fill },
|
|
.s = undefined,
|
|
.i = undefined,
|
|
};
|
|
|
|
pcg.seed(init_s);
|
|
return pcg;
|
|
}
|
|
|
|
fn next(self: *Pcg) u32 {
|
|
const l = self.s;
|
|
self.s = l *% default_multiplier +% (self.i | 1);
|
|
|
|
const xor_s = @truncate(u32, ((l >> 18) ^ l) >> 27);
|
|
const rot = @intCast(u32, l >> 59);
|
|
|
|
return (xor_s >> @intCast(u5, rot)) | (xor_s << @intCast(u5, (0 -% rot) & 31));
|
|
}
|
|
|
|
fn seed(self: *Pcg, init_s: u64) void {
|
|
// Pcg requires 128-bits of seed.
|
|
var gen = std.rand.SplitMix64.init(init_s);
|
|
self.seedTwo(gen.next(), gen.next());
|
|
}
|
|
|
|
fn seedTwo(self: *Pcg, init_s: u64, init_i: u64) void {
|
|
self.s = 0;
|
|
self.i = (init_s << 1) | 1;
|
|
self.s = self.s *% default_multiplier +% self.i;
|
|
self.s +%= init_i;
|
|
self.s = self.s *% default_multiplier +% self.i;
|
|
}
|
|
|
|
fn fill(r: *Random, buf: []u8) void {
|
|
const self = @fieldParentPtr(Pcg, "random", r);
|
|
|
|
var i: usize = 0;
|
|
const aligned_len = buf.len - (buf.len & 7);
|
|
|
|
// Complete 4 byte segments.
|
|
while (i < aligned_len) : (i += 4) {
|
|
var n = self.next();
|
|
comptime var j: usize = 0;
|
|
inline while (j < 4) : (j += 1) {
|
|
buf[i + j] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
|
|
// Remaining. (cuts the stream)
|
|
if (i != buf.len) {
|
|
var n = self.next();
|
|
while (i < buf.len) : (i += 1) {
|
|
buf[i] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
}
|
|
|
|
test "pcg sequence" {
|
|
var r = Pcg.init(0);
|
|
const s0: u64 = 0x9394bf54ce5d79de;
|
|
const s1: u64 = 0x84e9c579ef59bbf7;
|
|
r.seedTwo(s0, s1);
|
|
|
|
const seq = [_]u32{
|
|
2881561918,
|
|
3063928540,
|
|
1199791034,
|
|
2487695858,
|
|
1479648952,
|
|
3247963454,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
try std.testing.expect(s == r.next());
|
|
}
|
|
}
|
|
|
|
test "pcg fill" {
|
|
var r = Pcg.init(0);
|
|
const s0: u64 = 0x9394bf54ce5d79de;
|
|
const s1: u64 = 0x84e9c579ef59bbf7;
|
|
r.seedTwo(s0, s1);
|
|
|
|
const seq = [_]u32{
|
|
2881561918,
|
|
3063928540,
|
|
1199791034,
|
|
2487695858,
|
|
1479648952,
|
|
3247963454,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
var buf0: [4]u8 = undefined;
|
|
var buf1: [3]u8 = undefined;
|
|
std.mem.writeIntLittle(u32, &buf0, s);
|
|
Pcg.fill(&r.random, &buf1);
|
|
try std.testing.expect(std.mem.eql(u8, buf0[0..3], buf1[0..]));
|
|
}
|
|
}
|