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+--- Thread: WP34S: Question about Ran# in integer modes (/thread-157.html)
WP34S: Question about Ran# in integer modes - eri - 12-18-2013 08:33 PM
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?
RE: WP34S: Question about Ran# in integer modes - walter b - 12-18-2013 09:39 PM
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:-/
RE: WP34S: Question about Ran# in integer modes - Paul Dale - 12-19-2013 07:48 AM
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
RE: WP34S: Question about Ran# in integer modes - eri - 12-19-2013 08:08 AM
Thanks Paul, that's what I wanted to know. I see it there in stats_random. I was looking for handling of non-power of 2 bases. Why not handle that in the source?
Ok, I must be testing wrong. I'll try it on desktop for real.
RE: WP34S: Question about Ran# in integer modes - Paul Dale - 12-19-2013 09:11 AM
Is it really worth the space cost to provide non-binary base uniformly distributed random numbers? Use real mode, multiply and switch to integer.
- Pauli