[Rd] RNG.c: unif_rand, MARSAGLIA_MULTICARRY (PR#2437)

[Peter Dalgaard BSA]

simardr@IRO.UMontreal.CA writes:

> Full_Name: Richard Simard
> Version: 
> OS: Linux
> Submission from: (NULL) (132.204.25.139)
> 
> 
> In the random number generator MARSAGLIA_MULTICARRY, your algorithm is
> different than the one in the original reference that you give in the R manual:
> Marsaglia in his post to the mailing list {\it sci.stat.math} on September 29,
> 1997.
> The last line in the R program has a ^
> while Marsaglia's algorithm has a +.
> This gives very different random number generators.
> 
> The full line in RNG.c is:
>     return ((I1 << 16)^(I2 & 0177777)) * i2_32m1; /* in [0,1) */

Did you actually try that? 

As far as I can see the first operand will be (32-bit binary)

xxxxxxxxxxxxxxxx0000000000000000

and the other one is

0000000000000000xxxxxxxxxxxxxxxx

so it is the same whether you add them or use bitwise OR or
bitwise XOR.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907