WP34S: Question about Ran# in integer modes

12182013, 08:33 PM
Post: #1




WP34S: Question about Ran# in integer modes
I figure I can get random bits by switching to base 2, then hitting ran#, or change to base 6 and I can use the digits in place of a 6 sided dice.
When I do this and sum a random walk of various bits  or of all bits  the variance seems too small. The walk seems to land too close to zero to be uniform random. I glanced at the source code and the calculator is using a tausworthe generator from gnu science lib so either I'm testing the numbers incorrectly or the output is not what I assumed it was. Are digits uniform random when in an integer mode (base x)? Also, how to I read and set the seed for the random generator? 

12182013, 09:39 PM
Post: #2




RE: WP34S: Question about Ran# in integer modes
Quote:how to I read and set the seed for the random generator?To set, use SEED (see p. 112 of the printed manual). I don't know a way to read the seed though. d:/ 

12192013, 07:48 AM
Post: #3




RE: WP34S: Question about Ran# in integer modes
In integer mode, the random number generator is producing a sixty four bit random number using two sequential calls to the Tausworthe generator . This is then truncated and made unsigned according to the current mode (which will lose the sign bit and can change the bit pattern).
In binary or equivalent bases (4, 8 or 16), the digits should be completely random (at least in unsigned mode and most likely in all other modes). In other bases, there will be some small bias. Additionally, a shorter word length will increase the bias typically.  Pauli 

12192013, 08:08 AM
(This post was last modified: 12192013 08:10 AM by eri.)
Post: #4




RE: WP34S: Question about Ran# in integer modes
Thanks Paul, that's what I wanted to know. I see it there in stats_random. I was looking for handling of nonpower of 2 bases. Why not handle that in the source?
Ok, I must be testing wrong. I'll try it on desktop for real. 

12192013, 09:11 AM
(This post was last modified: 12202013 06:20 AM by Paul Dale.)
Post: #5




RE: WP34S: Question about Ran# in integer modes
Is it really worth the space cost to provide nonbinary base uniformly distributed random numbers? Use real mode, multiply and switch to integer.
 Pauli 

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