pseudorandom number generator I use sometimes

xorshift128plus.c

// based on V8 https://v8.dev/blog/math-random.
uint64_t state0 = 0x4D696B696E6C6579;
uint64_t state1 = 0x0000004873696E67;
uint64_t xorshift128plus() {
    uint64_t s1 = state0;
    uint64_t s0 = state1;
    state0 = s0;
    s1 ^= s1 << 23;
    s1 ^= s1 >> 17;
    s1 ^= s0;
    s1 ^= s0 >> 26;
    state1 = s1;
    return state0 + state1;
}