MRG32k3a Combined recursive generator (pseudo-code)

   /* Constants */
   /* First generator */
   a1 = [0, 1403580, -810728]
   m1 = 2**32 - 209
   /* Second Generator */
   a2 = [527612, 0, -1370589]
   m2 = 2**32 - 22853
    
   d = m1 + 1
   
   class MRG32k3a
       x1 = [0, 0, 0]  /* list of three last values of gen #1 */
       x2 = [0, 0, 0]  /* list of three last values of gen #2 */
       
       method seed(u64 seed_state)
           assert seed_state in range >0 and < d 
           x1 = [seed_state, 0, 0]
           x2 = [seed_state, 0, 0]
       end method
           
       method next_int()
           x1i = (a1[0]*x1[0] + a1[1]*x1[1] + a1[2]*x1[2]) mod m1
           x2i = (a2[0]*x2[0] + a2[1]*x2[1] + a2[2]*x2[2]) mod m2
           x1 = [x1i, x1[0], x1[1]]    /* Keep last three */
           x2 = [x2i, x2[0], x2[1]]    /* Keep last three */
           z = (x1i - x2i) % m1
           answer = (z + 1)
           
           return answer
       end method
       
       method next_float():
           return float next_int() / d
       end method
       
   end class


MRG32k3a Use:
   random_gen = instance MRG32k3a
   random_gen.seed(1234567)
   print(random_gen.next_int())   /* 1459213977 */
   print(random_gen.next_int())   /* 2827710106 */
   print(random_gen.next_int())   /* 4245671317 */
   print(random_gen.next_int())   /* 3877608661 */
   print(random_gen.next_int())   /* 2595287583 */
   
       

Task
 Generate a class/set of functions that generates pseudo-random
numbers as shown above.

 Show that the first five integers generated with the seed `1234567`
are as shown above

 Show that for an initial seed of '987654321' the counts of 100_000
repetitions of

   floor(random_gen.next_float() * 5)

Is as follows:

   0: 20002, 1: 20060, 2: 19948, 3: 20059, 4: 19931

 Show your output here, on this page.


import Data.List
 
randoms :: Int -> [Int]
randoms seed = unfoldr go ([seed,0,0],[seed,0,0])
  where
    go (x1,x2) =
      let x1i = sum (zipWith (*) x1 a1) `mod` m1
          x2i = sum (zipWith (*) x2 a2) `mod` m2
      in Just $ ((x1i - x2i) `mod` m1, (x1i:init x1, x2i:init x2))
 
    a1 = [0, 1403580, -810728]
    m1 = 2^32 - 209
    a2 = [527612, 0, -1370589]
    m2 = 2^32 - 22853
 
randomsFloat = map ((/ (2^32 - 208)) . fromIntegral) . randoms