> For initial experiments, there's already a site which stores the first > 200M digits of pi, for hobbyists wanting to do Carl Sagan > "Contact"-type research:
When I first read that in "Contact" years ago it knocked down by several notches my respect for the novel. Even the Almighty doesn't have any choice about the digits of π, right? What's He/She going to do about the various power series, f'instance? On Thu, Oct 27, 2011 at 5:26 AM, Ian Clark <[email protected]> wrote: > Being old enough to have learned my electronics before the digital > age, I wonder if it isn't time to reconsider shot noise as a source of > random numbers. It has a forensic advantage in lottery draws, and > monte-carlo simulations of fraught political topics like climate > change, by taking the "pseudo" out of "pseudo-random". > > For years the UK gov ran a device called ERNIE > http://en.wikipedia.org/wiki/ERNIE#ERNIE > to pick premium bonds (a savings scheme where the interest payable was > put in a monthly draw). > > A device to generate binary digits from electronic noise would be so > simple it ought to be fitted as standard to today's desktop computers. > Failing that, if I had a serious need for true random numbers I'd > experiment with an open microphone line using Audacity to save the > number stream as a WAV. > > Need a reproducible number stream? With the amount of free storage > space in the "cloud" (I currently have access to around 2 GB and I > don't remember asking for it) why not just store it? I also have a 1TB > disk drive, mostly lying empty. > > For initial experiments, there's already a site which stores the first > 200M digits of pi, for hobbyists wanting to do Carl Sagan > "Contact"-type research: > http://www.angio.net/pi/piquery > Aside: ought the hunt for meaningful sequences in pi to be called perimancy? > :-) > > > > On Fri, Oct 14, 2011 at 8:30 PM, Zsbán Ambrus <[email protected]> wrote: >> On Fri, Oct 14, 2011 at 2:33 PM, Zsbán Ambrus <[email protected]> wrote: >>> On Fri, Oct 14, 2011 at 1:08 PM, Ewart Shaw <[email protected]> wrote: >>>> I want to generate pseudorandom sequences that are the same for 32- & >>>> 64-bit J. >>> >>> Have you tried the other random generators the (9!:43) foreign makes >>> available? I'd guess some of them are the same for 32 and 64 bit J. >> >> Hmm, from a quick test, it seems Roger is right: none of the built in >> generators give the same results on the 32-bit and 64-bit J. >> >> Let's use the random generation functions from GSL ( >> http://www.gnu.org/software/gsl/ ) then. This example implements >> roll, but not deal. >> >> >> $ cat rngwrap.c >> #include <gsl/gsl_rng.h> >> >> /* >> Allocate a new random generator of the Mersenne Twister algorithm >> and initialize it with the default seed. >> */ >> gsl_rng * >> wrap_newrng(void) { >> gsl_rng *g = gsl_rng_alloc(gsl_rng_mt19937); >> return g; >> } >> >> $ cat rngwrap.ijs >> NB. random generator functions from GSL >> rngobj=: <'./rngwrap.so wrap_newrng > x'15!:0$0 >> rollint=: './rngwrap.so gsl_rng_uniform_int > x *c x'15!:0 rngobj;] >> rollflo=: './rngwrap.so gsl_rng_uniform_pos > d *c'15!:0 (,<rngobj)"_ >> roll=: rollflo`rollint`[:@.*"0 :[: >> >> $ gcc -Wall -O -fpic -lm -lgslcblas -lgsl -shared -o rngwrap.so rngwrap.c >> $ jconsole rngwrap.ijs >> roll (10$1e4),5$0 >> 9997 1629 2826 9472 2316 4849 9574 7443 5400 7399 0.759944 0.658637 >> 0.315638 0.804403 0.519672 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
