55 lines
1.1 KiB
C
55 lines
1.1 KiB
C
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#ifndef KRNG_H
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#define KRNG_H
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typedef struct {
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uint64_t s[2];
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} krng_t;
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static inline uint64_t kr_splitmix64(uint64_t x)
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{
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uint64_t z = (x += 0x9E3779B97F4A7C15ULL);
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z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ULL;
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z = (z ^ (z >> 27)) * 0x94D049BB133111EBULL;
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return z ^ (z >> 31);
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}
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static inline uint64_t kr_rand_r(krng_t *r)
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{
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const uint64_t s0 = r->s[0];
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uint64_t s1 = r->s[1];
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const uint64_t result = s0 + s1;
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s1 ^= s0;
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r->s[0] = (s0 << 55 | s0 >> 9) ^ s1 ^ (s1 << 14);
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r->s[1] = s0 << 36 | s0 >> 28;
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return result;
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}
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static inline void kr_jump_r(krng_t *r)
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{
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static const uint64_t JUMP[] = { 0xbeac0467eba5facbULL, 0xd86b048b86aa9922ULL };
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uint64_t s0 = 0, s1 = 0;
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int i, b;
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for (i = 0; i < 2; ++i)
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for (b = 0; b < 64; b++) {
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if (JUMP[i] & 1ULL << b)
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s0 ^= r->s[0], s1 ^= r->s[1];
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kr_rand_r(r);
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}
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r->s[0] = s0, r->s[1] = s1;
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}
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static inline void kr_srand_r(krng_t *r, uint64_t seed)
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{
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r->s[0] = kr_splitmix64(seed);
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r->s[1] = kr_splitmix64(r->s[0]);
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}
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static inline double kr_drand_r(krng_t *r)
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{
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union { uint64_t i; double d; } u;
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u.i = 0x3FFULL << 52 | kr_rand_r(r) >> 12;
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return u.d - 1.0;
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}
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#endif
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