Parameter that gives the maximum cycle

[Hal Dosen]

How do you determine the parameters that would give the maximum cycle in xoroshiro?

For example, what is the parameter that gives the maximum cycle in xoroshiro16++?

[Jsknkj RNG]

Disambiguate xoroshiro16++. Is it xoroshiro[8]16++ (two 8-bit integers), xoroshiro[4]16++ (four 4-bit integers), or xoroshiro[2]16++ (eight 2-bit integers)?

[Hal Dosen]

What I am is xoroshiro[8]16++ (two 8-bit integers).

My c code is here.

#include <stdint.h>

#include <stdio.h>

static inline uint8_t rotl(const uint8_t x, int k) {

return (x << k) | (x >> (8 - k));

}

static uint8_t s[2];

void seed(const uint8_t s0, const uint8_t s1){

  s[0] = s0;

  s[1] = s1;

}

uint8_t next(void) {

const uint8_t s0 = s[0];

uint8_t s1 = s[1];

const uint8_t result = rotl(s0 + s1, a) + s0;  //a

s1 ^= s0;

s[0] = rotl(s0, b) ^ s1 ^ (s1 << c); //  b, c

s[1] = rotl(s1, d); // d

return result;

}

int main(void){

  uint8_t s0 = 1;

  uint8_t s1 = 3;

  

  seed(s0, s1 + 1);

  

  uint8_t r;

  r = next();

  printf("%u\n",r);

  return 0;

}

I don't know what to set abcd to to get the maximum cycle.

As a side note, am I right in thinking that the maximum cycle of xoroshiro16++ is 2^16-1?

2021年10月31日日曜日 19:30:02 UTC+9 uiopzx...@gmail.com: