1 /* Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
3 To the extent possible under law, the author has dedicated all copyright
4 and related and neighboring rights to this software to the public domain
5 worldwide. This software is distributed without any warranty.
7 See <http://creativecommons.org/publicdomain/zero/1.0/>. */
11 /* This is xoshiro256+ 1.0, our best and fastest generator for floating-point
12 numbers. We suggest to use its upper bits for floating-point
13 generation, as it is slightly faster than xoshiro256++/xoshiro256**. It
14 passes all tests we are aware of except for the lowest three bits,
15 which might fail linearity tests (and just those), so if low linear
16 complexity is not considered an issue (as it is usually the case) it
17 can be used to generate 64-bit outputs, too.
19 We suggest to use a sign test to extract a random Boolean value, and
20 right shifts to extract subsets of bits.
22 The state must be seeded so that it is not everywhere zero. If you have
23 a 64-bit seed, we suggest to seed a splitmix64 generator and use its
27 static inline uint64_t rotl(const uint64_t x, int k) {
28 return (x << k) | (x >> (64 - k));
35 const uint64_t result = s[0] + s[3];
37 const uint64_t t = s[1] << 17;
46 s[3] = rotl(s[3], 45);
52 /* This is the jump function for the generator. It is equivalent
53 to 2^128 calls to next(); it can be used to generate 2^128
54 non-overlapping subsequences for parallel computations. */
57 static const uint64_t JUMP[] = { 0x180ec6d33cfd0aba, 0xd5a61266f0c9392c, 0xa9582618e03fc9aa, 0x39abdc4529b1661c };
63 for(int i = 0; i < sizeof JUMP / sizeof *JUMP; i++)
64 for(int b = 0; b < 64; b++) {
65 if (JUMP[i] & UINT64_C(1) << b) {
81 /* This is the long-jump function for the generator. It is equivalent to
82 2^192 calls to next(); it can be used to generate 2^64 starting points,
83 from each of which jump() will generate 2^64 non-overlapping
84 subsequences for parallel distributed computations. */
86 void long_jump(void) {
87 static const uint64_t LONG_JUMP[] = { 0x76e15d3efefdcbbf, 0xc5004e441c522fb3, 0x77710069854ee241, 0x39109bb02acbe635 };
93 for(int i = 0; i < sizeof LONG_JUMP / sizeof *LONG_JUMP; i++)
94 for(int b = 0; b < 64; b++) {
95 if (LONG_JUMP[i] & UINT64_C(1) << b) {