1 // Copyright 2018 Developers of the Rand project.
2 //
3 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6 // option. This file may not be copied, modified, or distributed
7 // except according to those terms.
8 
9 //! The implementations of the `Standard` distribution for integer types.
10 
11 use crate::distributions::{Distribution, Standard};
12 use crate::Rng;
13 #[cfg(all(target_arch = "x86", feature = "simd_support"))]
14 use core::arch::x86::{__m128i, __m256i};
15 #[cfg(all(target_arch = "x86_64", feature = "simd_support"))]
16 use core::arch::x86_64::{__m128i, __m256i};
17 use core::num::{NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize,
18     NonZeroU128};
19 #[cfg(feature = "simd_support")] use packed_simd::*;
20 
21 impl Distribution<u8> for Standard {
22     #[inline]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u823     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u8 {
24         rng.next_u32() as u8
25     }
26 }
27 
28 impl Distribution<u16> for Standard {
29     #[inline]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u1630     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u16 {
31         rng.next_u32() as u16
32     }
33 }
34 
35 impl Distribution<u32> for Standard {
36     #[inline]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u3237     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u32 {
38         rng.next_u32()
39     }
40 }
41 
42 impl Distribution<u64> for Standard {
43     #[inline]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u6444     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64 {
45         rng.next_u64()
46     }
47 }
48 
49 impl Distribution<u128> for Standard {
50     #[inline]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u12851     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u128 {
52         // Use LE; we explicitly generate one value before the next.
53         let x = u128::from(rng.next_u64());
54         let y = u128::from(rng.next_u64());
55         (y << 64) | x
56     }
57 }
58 
59 impl Distribution<usize> for Standard {
60     #[inline]
61     #[cfg(any(target_pointer_width = "32", target_pointer_width = "16"))]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize62     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
63         rng.next_u32() as usize
64     }
65 
66     #[inline]
67     #[cfg(target_pointer_width = "64")]
sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize68     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
69         rng.next_u64() as usize
70     }
71 }
72 
73 macro_rules! impl_int_from_uint {
74     ($ty:ty, $uty:ty) => {
75         impl Distribution<$ty> for Standard {
76             #[inline]
77             fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
78                 rng.gen::<$uty>() as $ty
79             }
80         }
81     };
82 }
83 
84 impl_int_from_uint! { i8, u8 }
85 impl_int_from_uint! { i16, u16 }
86 impl_int_from_uint! { i32, u32 }
87 impl_int_from_uint! { i64, u64 }
88 impl_int_from_uint! { i128, u128 }
89 impl_int_from_uint! { isize, usize }
90 
91 macro_rules! impl_nzint {
92     ($ty:ty, $new:path) => {
93         impl Distribution<$ty> for Standard {
94             fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
95                 loop {
96                     if let Some(nz) = $new(rng.gen()) {
97                         break nz;
98                     }
99                 }
100             }
101         }
102     };
103 }
104 
105 impl_nzint!(NonZeroU8, NonZeroU8::new);
106 impl_nzint!(NonZeroU16, NonZeroU16::new);
107 impl_nzint!(NonZeroU32, NonZeroU32::new);
108 impl_nzint!(NonZeroU64, NonZeroU64::new);
109 impl_nzint!(NonZeroU128, NonZeroU128::new);
110 impl_nzint!(NonZeroUsize, NonZeroUsize::new);
111 
112 #[cfg(feature = "simd_support")]
113 macro_rules! simd_impl {
114     ($(($intrinsic:ident, $vec:ty),)+) => {$(
115         impl Distribution<$intrinsic> for Standard {
116             #[inline]
117             fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $intrinsic {
118                 $intrinsic::from_bits(rng.gen::<$vec>())
119             }
120         }
121     )+};
122 
123     ($bits:expr,) => {};
124     ($bits:expr, $ty:ty, $($ty_more:ty,)*) => {
125         simd_impl!($bits, $($ty_more,)*);
126 
127         impl Distribution<$ty> for Standard {
128             #[inline]
129             fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
130                 let mut vec: $ty = Default::default();
131                 unsafe {
132                     let ptr = &mut vec;
133                     let b_ptr = &mut *(ptr as *mut $ty as *mut [u8; $bits/8]);
134                     rng.fill_bytes(b_ptr);
135                 }
136                 vec.to_le()
137             }
138         }
139     };
140 }
141 
142 #[cfg(feature = "simd_support")]
143 simd_impl!(16, u8x2, i8x2,);
144 #[cfg(feature = "simd_support")]
145 simd_impl!(32, u8x4, i8x4, u16x2, i16x2,);
146 #[cfg(feature = "simd_support")]
147 simd_impl!(64, u8x8, i8x8, u16x4, i16x4, u32x2, i32x2,);
148 #[cfg(feature = "simd_support")]
149 simd_impl!(128, u8x16, i8x16, u16x8, i16x8, u32x4, i32x4, u64x2, i64x2,);
150 #[cfg(feature = "simd_support")]
151 simd_impl!(256, u8x32, i8x32, u16x16, i16x16, u32x8, i32x8, u64x4, i64x4,);
152 #[cfg(feature = "simd_support")]
153 simd_impl!(512, u8x64, i8x64, u16x32, i16x32, u32x16, i32x16, u64x8, i64x8,);
154 #[cfg(all(
155     feature = "simd_support",
156     any(target_arch = "x86", target_arch = "x86_64")
157 ))]
158 simd_impl!((__m128i, u8x16), (__m256i, u8x32),);
159 
160 #[cfg(test)]
161 mod tests {
162     use super::*;
163 
164     #[test]
test_integers()165     fn test_integers() {
166         let mut rng = crate::test::rng(806);
167 
168         rng.sample::<isize, _>(Standard);
169         rng.sample::<i8, _>(Standard);
170         rng.sample::<i16, _>(Standard);
171         rng.sample::<i32, _>(Standard);
172         rng.sample::<i64, _>(Standard);
173         rng.sample::<i128, _>(Standard);
174 
175         rng.sample::<usize, _>(Standard);
176         rng.sample::<u8, _>(Standard);
177         rng.sample::<u16, _>(Standard);
178         rng.sample::<u32, _>(Standard);
179         rng.sample::<u64, _>(Standard);
180         rng.sample::<u128, _>(Standard);
181     }
182 
183     #[test]
value_stability()184     fn value_stability() {
185         fn test_samples<T: Copy + core::fmt::Debug + PartialEq>(zero: T, expected: &[T])
186         where Standard: Distribution<T> {
187             let mut rng = crate::test::rng(807);
188             let mut buf = [zero; 3];
189             for x in &mut buf {
190                 *x = rng.sample(Standard);
191             }
192             assert_eq!(&buf, expected);
193         }
194 
195         test_samples(0u8, &[9, 247, 111]);
196         test_samples(0u16, &[32265, 42999, 38255]);
197         test_samples(0u32, &[2220326409, 2575017975, 2018088303]);
198         test_samples(0u64, &[
199             11059617991457472009,
200             16096616328739788143,
201             1487364411147516184,
202         ]);
203         test_samples(0u128, &[
204             296930161868957086625409848350820761097,
205             145644820879247630242265036535529306392,
206             111087889832015897993126088499035356354,
207         ]);
208         #[cfg(any(target_pointer_width = "32", target_pointer_width = "16"))]
209         test_samples(0usize, &[2220326409, 2575017975, 2018088303]);
210         #[cfg(target_pointer_width = "64")]
211         test_samples(0usize, &[
212             11059617991457472009,
213             16096616328739788143,
214             1487364411147516184,
215         ]);
216 
217         test_samples(0i8, &[9, -9, 111]);
218         // Skip further i* types: they are simple reinterpretation of u* samples
219 
220         #[cfg(feature = "simd_support")]
221         {
222             // We only test a sub-set of types here and make assumptions about the rest.
223 
224             test_samples(u8x2::default(), &[
225                 u8x2::new(9, 126),
226                 u8x2::new(247, 167),
227                 u8x2::new(111, 149),
228             ]);
229             test_samples(u8x4::default(), &[
230                 u8x4::new(9, 126, 87, 132),
231                 u8x4::new(247, 167, 123, 153),
232                 u8x4::new(111, 149, 73, 120),
233             ]);
234             test_samples(u8x8::default(), &[
235                 u8x8::new(9, 126, 87, 132, 247, 167, 123, 153),
236                 u8x8::new(111, 149, 73, 120, 68, 171, 98, 223),
237                 u8x8::new(24, 121, 1, 50, 13, 46, 164, 20),
238             ]);
239 
240             test_samples(i64x8::default(), &[
241                 i64x8::new(
242                     -7387126082252079607,
243                     -2350127744969763473,
244                     1487364411147516184,
245                     7895421560427121838,
246                     602190064936008898,
247                     6022086574635100741,
248                     -5080089175222015595,
249                     -4066367846667249123,
250                 ),
251                 i64x8::new(
252                     9180885022207963908,
253                     3095981199532211089,
254                     6586075293021332726,
255                     419343203796414657,
256                     3186951873057035255,
257                     5287129228749947252,
258                     444726432079249540,
259                     -1587028029513790706,
260                 ),
261                 i64x8::new(
262                     6075236523189346388,
263                     1351763722368165432,
264                     -6192309979959753740,
265                     -7697775502176768592,
266                     -4482022114172078123,
267                     7522501477800909500,
268                     -1837258847956201231,
269                     -586926753024886735,
270                 ),
271             ]);
272         }
273     }
274 }
275