GNU Radio Manual and C++ API Reference 3.9.4.0
The Free & Open Software Radio Ecosystem
xoroshiro128p.h
Go to the documentation of this file.
1/*
2 * Copyright 2018 Free Software Foundation, Inc.
3 *
4 * This file is part of GNU Radio
5 *
6 * SPDX-License-Identifier: GPL-3.0-or-later
7 *
8 */
9
10// Built on XOROSHIRO128+ by David Blackman and Sebastiano Vigna who put this
11// under CC-0, colloquially known as "public domain (or as close you get to that
12// in your local legislation)" see
13// http://xoroshiro.di.unimi.it/xoroshiro128plus.c
14// Conversion to a local state (original used global state) done by Marcus
15// Müller, 2018.
16#ifndef INCLUDED_XOROSHIRO128P_H
17#define INCLUDED_XOROSHIRO128P_H
18#ifdef __cplusplus
19extern "C" {
20#endif
21
22#include <cstdint>
23
24/*! \brief rotating left shift helper
25 * According to the original authors, this will on most platforms reduce to a single
26 * instruction
27 */
28static inline uint64_t rotl(const uint64_t x, const int k)
29{
30 return (x << k) | (x >> (64 - k));
31}
32
33
34/*! \brief generate the next random number and update the state.
35 * This is the workhorse, here!
36 */
37static inline uint64_t xoroshiro128p_next(uint64_t* state)
38{
39 const uint64_t s0 = state[0];
40 uint64_t s1 = state[1];
41 const uint64_t result = s0 + s1;
42
43 s1 ^= s0;
44 state[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14); // a, b
45 state[1] = rotl(s1, 36); // c
46
47 return result;
48}
49
50
51/*! \brief Advance the internal state by 2^64 steps; useful when coordinating multiple
52 independent RNGs This is the jump function for the generator. It is equivalent to 2^64
53 calls to next(); it can be used to generate 2^64 non-overlapping subsequences for
54 parallel computations. */
55static inline void xoroshiro128p_jump(uint64_t* state)
56{
57 static const uint64_t JUMP[] = { 0xbeac0467eba5facb, 0xd86b048b86aa9922 };
58
59 uint64_t s0 = 0;
60 uint64_t s1 = 0;
61 for (unsigned int i = 0; i < sizeof(JUMP) / sizeof(*JUMP); ++i) {
62 for (unsigned int b = 0; b < 64; ++b) {
63 if (JUMP[i] & UINT64_C(1) << b) {
64 s0 ^= state[0];
65 s1 ^= state[1];
66 }
67 xoroshiro128p_next(state);
68 }
69 }
70
71 state[0] = s0;
72 state[1] = s1;
73}
74
75/*! \brief step of the SPLITMIX64 RNG; only used internally for seeding
76 * This RNG isn't as good as XOROSHIRO128+, so it's only used to initialize a 128 bit
77 * state from a seed.
78 */
79static inline uint64_t splitmix64_next(uint64_t* state)
80{
81 uint64_t z = (*state += 0x9e3779b97f4a7c15);
82 z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
83 z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
84 return z ^ (z >> 31);
85}
86
87/*! \brief Seed the 128 bit state from a 64 bit seed
88 */
89static inline void xoroshiro128p_seed(uint64_t* state, const uint64_t seed)
90{
91 state[0] = seed;
92 state[1] = splitmix64_next(state);
93 xoroshiro128p_jump(state);
94}
95#ifdef __cplusplus
96}
97#endif
98#endif // Include guard
static void xoroshiro128p_seed(uint64_t *state, const uint64_t seed)
Seed the 128 bit state from a 64 bit seed.
Definition: xoroshiro128p.h:89
static uint64_t splitmix64_next(uint64_t *state)
step of the SPLITMIX64 RNG; only used internally for seeding This RNG isn't as good as XOROSHIRO128+,...
Definition: xoroshiro128p.h:79
static void xoroshiro128p_jump(uint64_t *state)
Advance the internal state by 2^64 steps; useful when coordinating multiple independent RNGs This is ...
Definition: xoroshiro128p.h:55
static uint64_t rotl(const uint64_t x, const int k)
rotating left shift helper According to the original authors, this will on most platforms reduce to a...
Definition: xoroshiro128p.h:28
static uint64_t xoroshiro128p_next(uint64_t *state)
generate the next random number and update the state. This is the workhorse, here!
Definition: xoroshiro128p.h:37