tinymt 1.0.9

Rust implementation of TinyMT 64/32 - a lightweight variant of Mersenne Twister PRNG
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211

use core::cmp::min;

use crate::TinyMT64;

const TINYMT64_MEXP: usize = 127;
const TINYMT64_SH0: u64 = 12;
const TINYMT64_SH1: u64 = 11;
const TINYMT64_SH8: u64 = 8;
const TINYMT64_MASK: u64 = 0x7fff_ffff_ffff_ffff_u64;
const TINYMT64_MUL: f64 = 1.0 / 9_007_199_254_740_992.0;
const MIN_LOOP: usize = 8;

impl TinyMT64 {
  pub fn new(status: [u64; 2], mat1: u32, mat2: u32, tmat: u64) -> TinyMT64 {
    TinyMT64 { status, mat1, mat2, tmat }
  }
}

/// This function represents a function used in the initialization by init_by_array.
#[inline]
fn ini_func1(x: u64) -> u64 {
  (x ^ (x >> 59)).wrapping_mul(2_173_292_883_993_u64)
}

/// This function represents a function used in the initialization by init_by_array
#[inline]
fn ini_func2(x: u64) -> u64 {
  (x ^ (x >> 59)).wrapping_mul(58_885_565_329_898_161_u64)
}

/// This function certificate the period of 2^127-1.
#[inline]
fn period_certification(random: &mut TinyMT64) {
  if random.status[0] & TINYMT64_MASK == 0 && random.status[1] == 0 {
    random.status[0] = 'T' as u64;
    random.status[1] = 'M' as u64;
  }
}

/// This function initializes the internal state array with a 64-bit unsigned integer seed.
/// @param seed a 64-bit unsigned integer used as a seed.
pub fn tinymt64_init(random: &mut TinyMT64, seed: u64) {
  random.status[0] = seed ^ ((random.mat1 as u64) << 32);
  random.status[1] = (random.mat2 as u64) ^ random.tmat;
  for i in 1..MIN_LOOP {
    random.status[i & 1] ^= (i as u64).wrapping_add(
      6_364_136_223_846_793_005_u64
        .wrapping_mul(random.status[(i - 1) & 1] ^ (random.status[(i - 1) & 1] >> 62)),
    );
  }
  period_certification(random);
}

/// This function initializes the internal state array, with an array of 64-bit unsigned integers used as seeds
/// @param init_key the array of 64-bit integers, used as a seed.
/// @param key_length the length of init_key.
pub fn tinymt64_init_by_array(random: &mut TinyMT64, init_key: &[u64]) {
  let lag: usize = 1;
  let mid: usize = 1;
  let size: usize = 4;
  let key_length: usize = init_key.len();

  let mut st: [u64; 4] = [0, random.mat1 as u64, random.mat2 as u64, random.tmat];
  let mut count: usize = if key_length + 1 > MIN_LOOP { key_length + 1 } else { MIN_LOOP };
  let mut r: u64 = ini_func1(st[0] ^ st[mid % size] ^ st[(size - 1) % size]);
  st[mid % size] += r;
  r += key_length as u64;
  st[(mid + lag) % size] += r;
  st[0] = r;
  count -= 1;
  let mut i = 1;
  let boundary = min(count, key_length);
  for key in init_key.iter().take(boundary) {
    r = ini_func1(st[i] ^ st[(i + mid) % size] ^ st[(i + size - 1) % size]);
    st[(i + mid) % size] = st[(i + mid) % size].wrapping_add(r);
    r += key + i as u64;
    st[(i + mid + lag) % size] = st[(i + mid + lag) % size].wrapping_add(r);
    st[i] = r;
    i = (i + 1) % size;
  }
  for _ in boundary..count {
    r = ini_func1(st[i] ^ st[(i + mid) % size] ^ st[(i + size - 1) % size]);
    st[(i + mid) % size] = st[(i + mid) % size].wrapping_add(r);
    r += i as u64;
    st[(i + mid + lag) % size] = st[(i + mid + lag) % size].wrapping_add(r);
    st[i] = r;
    i = (i + 1) % size;
  }
  for _ in 0..size {
    r = ini_func2(st[i].wrapping_add(st[(i + mid) % size]).wrapping_add(st[(i + size - 1) % size]));
    st[(i + mid) % size] ^= r;
    r -= i as u64;
    st[(i + mid + lag) % size] ^= r;
    st[i] = r;
    i = (i + 1) % size;
  }
  random.status[0] = st[0] ^ st[1];
  random.status[1] = st[2] ^ st[3];
  period_certification(random);
}

/// This function always returns 127.
#[inline]
pub fn tinymt64_get_mexp(_: &TinyMT64) -> usize {
  TINYMT64_MEXP
}

/**
 * This function changes internal state of tinymt64. Users should not call this function directly.
 * @param random tinymt internal status
 */
#[inline]
pub fn tinymt64_next_state(random: &mut TinyMT64) {
  random.status[0] &= TINYMT64_MASK;
  let mut x: u64 = random.status[0] ^ random.status[1];
  x ^= x << TINYMT64_SH0;
  x ^= x >> 32;
  x ^= x << 32;
  x ^= x << TINYMT64_SH1;
  random.status[0] = random.status[1];
  random.status[1] = x;
  random.status[0] ^= (-((x & 1) as i64) as u64) & (random.mat1 as u64);
  random.status[1] ^= (-((x & 1) as i64) as u64) & ((random.mat2 as u64) << 32);
}

/// This function outputs 64-bit unsigned integer from internal state. Users should not call this function directly.
/// @return 64-bit unsigned pseudorandom number
#[inline]
pub fn tinymt64_temper(random: &TinyMT64) -> u64 {
  // defined(LINEARITY_CHECK)
  // x = random->status[0] ^ random->status[1];
  let mut x = random.status[0].wrapping_add(random.status[1]);
  x ^= random.status[0] >> TINYMT64_SH8;
  x ^ (-((x & 1) as i64) as u64) & random.tmat
}

/// This function outputs floating point number from internal state. Users should not call this function directly.
/// @return floating point number r (1.0 <= r < 2.0)
#[inline]
pub fn tinymt64_temper_conv(random: &TinyMT64) -> f64 {
  // defined(LINEARITY_CHECK)
  // x = random->status[0] ^ random->status[1];
  let mut x = random.status[0].wrapping_add(random.status[1]);
  x ^= random.status[0] >> TINYMT64_SH8;
  x = ((x ^ ((-((x & 1) as i64) as u64) & random.tmat)) >> 12) | 0x3ff0_0000_0000_0000_u64;
  f64::from_le_bytes(x.to_le_bytes())
}

/// This function outputs floating point number from internal state. Users should not call this function directly.
/// @return floating point number r (1.0 < r < 2.0)
#[inline]
pub fn tinymt64_temper_conv_open(random: &TinyMT64) -> f64 {
  // defined(LINEARITY_CHECK)
  // x = random->status[0] ^ random->status[1];
  let mut x = random.status[0].wrapping_add(random.status[1]);
  x ^= random.status[0] >> TINYMT64_SH8;
  x = ((x ^ ((-((x & 1) as i64) as u64) & random.tmat)) >> 12) | 0x3ff0_0000_0000_0001_u64;
  f64::from_le_bytes(x.to_le_bytes())
}

/// This function outputs 64-bit unsigned integer from internal state.
/// @return 64-bit unsigned integer r (0 <= r < 2^64)
#[inline]
pub fn tinymt64_generate_uint64(random: &mut TinyMT64) -> u64 {
  tinymt64_next_state(random);
  tinymt64_temper(random)
}

/// This function outputs floating point number from internal state. This function is implemented
/// using multiplying by (1 / 2^53).
/// @return floating point number r (0.0 <= r < 1.0)
#[inline]
pub fn tinymt64_generate_double(random: &mut TinyMT64) -> f64 {
  tinymt64_next_state(random);
  ((tinymt64_temper(random) >> 11) as f64) * TINYMT64_MUL
}

/// This function outputs floating point number from internal state. This function is implemented
/// using union trick.
/// @return floating point number r (0.0 <= r < 1.0)
#[inline]
pub fn tinymt64_generate_double01(random: &mut TinyMT64) -> f64 {
  tinymt64_next_state(random);
  tinymt64_temper_conv(random) - 1.0
}

/// This function outputs floating point number from internal state. This function is implemented
/// using union trick.
/// @return floating point number r (1.0 <= r < 2.0)
#[inline]
pub fn tinymt64_generate_double12(random: &mut TinyMT64) -> f64 {
  tinymt64_next_state(random);
  tinymt64_temper_conv(random)
}

/// This function outputs floating point number from internal state. This function is implemented
/// using union trick.
/// @return floating point number r (0.0 < r <= 1.0)
#[inline]
pub fn tinymt64_generate_double_oc(random: &mut TinyMT64) -> f64 {
  tinymt64_next_state(random);
  2.0 - tinymt64_temper_conv(random)
}

/// This function outputs floating point number from internal state. This function is implemented
/// using union trick.
/// @return floating point number r (0.0 < r < 1.0)
pub fn tinymt64_generate_double_oo(random: &mut TinyMT64) -> f64 {
  tinymt64_next_state(random);
  tinymt64_temper_conv_open(random) - 1.0
}