xoroshiro.h

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#pragma once
 
#include <stdint.h>
 
#define rotl(x, k) (((x) << (k)) | ((x) >> (64 - (k))))
 
#define random_u64(rng_s)                                               \
__extension__ ({                                                        \
        const uint64_t __res = rotl((rng_s)[1] * 5, 7) * 9;             \
        const uint64_t __t = (rng_s)[1] << 17;                          \
                                                                        \
        (rng_s)[2] ^= (rng_s)[0];                                       \
        (rng_s)[3] ^= (rng_s)[1];                                       \
        (rng_s)[1] ^= (rng_s)[2];                                       \
        (rng_s)[0] ^= (rng_s)[3];                                       \
        (rng_s)[2] ^= __t;                                              \
        (rng_s)[3] = rotl((rng_s)[3], 45);                              \
                                                                        \
        __res;                                                          \
})
 
// FIXME: this is a very poor way to seed the generator
#define random_init(rng_s, llid, seed)                                  \
__extension__ ({                                                        \
        (rng_s)[0] = (llid + 1) * UINT64_C(16232384076195101791) ^ seed;\
        (rng_s)[1] = (llid + 1) * UINT64_C(13983006573105492179) ^ seed;\
        (rng_s)[2] = (llid + 1) * UINT64_C(10204677566545858177) ^ seed;\
        (rng_s)[3] = (llid + 1) * UINT64_C(14539058011249359317) ^ seed;\
        unsigned __i = 1024;                                            \
        while (__i--)                                                   \
                random_u64((rng_s));                                    \
})