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41 lines
1.2 KiB
C
41 lines
1.2 KiB
C
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/*
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* Xorshift Pseudo Random Number Generator based on work by David Blackman
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* and Sebastiano Vigna (vigna@acm.org).
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*
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* "Further scramblings of Marsaglia's xorshift generators"
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* http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
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* http://prng.di.unimi.it/xoroshiro128plusplus.c
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*
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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. This software is distributed without any warranty.
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*
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* See <http://creativecommons.org/publicdomain/zero/1.0/>.
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*
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* This is xoroshiro128++ 1.0, one of our all-purpose, rock-solid,
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* small-state generators. It is extremely (sub-ns) fast and it passes all
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* tests we are aware of, but its state space is large enough only for
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* mild parallelism.
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*/
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#include <sys/vdev_draid.h>
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static inline uint64_t rotl(const uint64_t x, int k)
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{
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return (x << k) | (x >> (64 - k));
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}
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uint64_t
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vdev_draid_rand(uint64_t *s)
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{
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const uint64_t s0 = s[0];
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uint64_t s1 = s[1];
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const uint64_t result = rotl(s0 + s1, 17) + s0;
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s1 ^= s0;
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s[0] = rotl(s0, 49) ^ s1 ^ (s1 << 21); // a, b
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s[1] = rotl(s1, 28); // c
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return (result);
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}
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