On Sat, 25 Apr 2015 18:31:24 +1000, "David Eather"
wrote:

On Sat, 25 Apr 2015 12:46:57 +1000, John Larkin
wrote:

On Sat, 25 Apr 2015 11:17:52 +1000, "David Eather"
wrote:

On Fri, 24 Apr 2015 10:59:43 +1000, John Fields
wrote:

On Thu, 23 Apr 2015 09:02:02 -0700, John Larkin
wrote:

On Sun, 19 Apr 2015 02:15:07 -0500, John Fields
wrote:

On 19 Apr 2015 03:14:30 GMT, Jasen Betts wrote:

On 2015-04-18, David Eather wrote:
On Thu, 02 Apr 2015 20:42:50 +1000, Jasen Betts
wrote:


I was wondering about that myself... I'll see if there's a cure.

r=(75*r+74)%65537 visits 0-65535 with no gaps.

not that i'd want to build it using 74LS logic.


That is an absolute turd. It screws up if the cycle tries to repeat
more
than once - it not longer visits 0 - 65535 without gaps (it
outputs a
665536 which needs 17 bits) and will miss a 16 bit number every
cycle
after the first, OR if the 17-th bit is ignored it will produce an
excess
number of zeros.

No, that is absolute bull****.

it's this:
http://en.wikipedia.org/wiki/Lehmer_...mber_generator

except offset by -1 so that the Lehmer zero state (which is
disallowed) is excluded and the maximal state fits in 16 bits.

---
If the all-zeroes state is disallowed, then there'll always be a
bias on the output.

The circuit I posted includes the all-zeroes state and, in fact, all
of its dflops are/can be cleared in order to initialize it.

John Fields

We are just finishing up a waveform generator box that includes two
programmable-bandwidth Gaussian analog noise generators. We used 47
and 49 bit maximal-length shift registers, clocked at 64 MHz. We just
peek at 18 bits of each register whenever we want a random number. An
asymmetry of one code out of 2^48 is not a big concern.

---
But, regardless of your machinations, it still isn't truly random,
is it?

John Fields


A paraphrase:
"anyone who believes a deterministic circuit can produce true randomness
is in a state of sin"

So, we have preceded from the philosophical to the theological.



No, from speculation to Shannon.

We have spent the last month or so doing amazing things around the
Sampling Theorem. My customers aren't going to believe some of the
things the Wayback Machine can do, and I'm trying to write some manual
content that will convince them that what we're claiming is possible.
Sadly, few engineers have heard of the Sampling Theorem and even fewer
understand it.

What did Shannon say about deterministic circuits and truly random
noise?

Good book: The Idea Factory by Jon Gertner, about the glory days of
Bell Labs. One cool point is that most people who did great work at
Bell had breakfast or lunch with Harry Nyquist.

There is another book called The Idea Factory, about being a student
at MIT.


--

John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com