38 lines
1.2 KiB
C
38 lines
1.2 KiB
C
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// /**
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// * A sufficient Pseudo-Random-Number-Generators (PRNG) of the Xorshift family
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// *
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// * For single threaded operations the PRNG provided by `R` are prefered. But they
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// * are _not_ thread save. The following is a simple PRNG usable in a multi-threaded
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// * application.
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// *
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// * See TODO: ...https://en.wikipedia.org/wiki/Xorshift
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// * SchachHoernchen
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// */
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// #ifndef INCLUDE_GUARD_RANDOM_H
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// #define INCLUDE_GUARD_RANDOM_H
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// #include <stdint.h> // uint32_t, uint64_t
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// static inline uint64_t rot64(uint64_t val, int shift) {
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// return (val << shift) | (val >> (64 - shift));
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// }
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// // PRNG of the Xorshift family
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// // @note the least significant 32 bits are not reliable, use most significant 32 bits
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// static inline uint64_t rand_u64(uint64_t seed[4]) {
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// uint64_t e = seed[0] - rot64(seed[1], 7);
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// seed[0] = seed[1] ^ rot64(seed[1], 13);
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// seed[1] = seed[2] + rot64(seed[3], 37);
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// seed[2] = seed[3] + e;
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// seed[3] = e + seed[0];
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// return seed[3];
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// }
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// static inline double unif_rand_u64(uint64_t seed[4]) {
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// return ((double)(rand_u64(seed) >> 32)) / (double)(-(uint32_t)1);
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// }
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// #endif
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