51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
// https://prng.di.unimi.it/xoroshiro64starstar.c
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/* Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
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To the extent possible under law, the author has dedicated all copyright
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and related and neighboring rights to this software to the public domain
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worldwide.
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
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IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#include <stdint.h>
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/* This is xoroshiro64** 1.0, our 32-bit all-purpose, rock-solid,
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small-state generator. It is extremely fast and it passes all tests we
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are aware of, but its state space is not large enough for any parallel
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application.
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For generating just single-precision (i.e., 32-bit) floating-point
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numbers, xoroshiro64* is even faster.
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The state must be seeded so that it is not everywhere zero. */
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static inline uint32_t rotl(const uint32_t x, int k) {
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return (x << k) | (x >> (32 - k));
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}
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static uint32_t s[2];
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uint32_t next(void) {
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const uint32_t s0 = s[0];
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uint32_t s1 = s[1];
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const uint32_t result = rotl(s0 * 0x9E3779BB, 5) * 5;
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s1 ^= s0;
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s[0] = rotl(s0, 26) ^ s1 ^ (s1 << 9); // a, b
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s[1] = rotl(s1, 13); // c
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return result;
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}
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