NICK@AI.AI.MIT.EDU (Nick Papadakis) (06/02/88)
Date: Sun, 29 May 88 09:00 EDT From: Antti Ylikoski <ayl%hutds.hut.fi%FINGATE.BITNET@MITVMA.MIT.EDU> To: AIList@AI.AI.MIT.EDU Subject: randomness cc: ayl@hutds.hut.fi In AIList Digest V7 #4, Barry Kort writes: >If I wanted to give my von Neumann machine a *true* random number >generator, I would connect it to an A/D converter driven by thermal >noise (i.e. a toasty resister). I recall that a Zener diode is a good source of noise (but cannot remember the spectrum it gives). It could be a good idea to utilize a Zener / A-D converter random number generator in Monte Carlo simulations. Andy Ylikoski PS. A pearl: Orthodox Christianity: Baruch Ha Ba, B'Shem Adonnnnnai
NICK@AI.AI.MIT.EDU (Nick Papadakis) (06/06/88)
To: ayl%hutds.hut.fi%FINGATE.BITNET@mitvma.mit.edu cc: AIList@ai.ai.mit.edu In-reply-to: Antti Ylikoski's message of Sun, 29 May 88 11:00:20 -0200 Subject: randomness Reply-To: aboulanger@bbn.com Date: Sat, 4 Jun 88 17:48 EDT From: aboulang@WILMA.BBN.COM Sender: aboulang@WILMA.BBN.COM In AIList Digest V7 #4, Barry Kort writes: >If I wanted to give my von Neumann machine a *true* random number >generator, I would connect it to an A/D converter driven by thermal >noise (i.e. a toasty resister). I recall that a Zener diode is a good source of noise (but cannot remember the spectrum it gives). It could be a good idea to utilize a Zener / A-D converter random number generator in Monte Carlo simulations. Andy Ylikoski Ahem, all this stuff about analog sources being better random sources is a bit of a "scientific" urban myth. It is instructive to go back to the papers of the early 60's and see what it took to utilize analog random sources. The basic problem in analog sources is correlation. To wit: "A Hybrid Analog-Digital Pseudo-Random Noise Generator", R.L.T. Hampton, AFIPS Conference Proceedings, Vol 25, 1964 Spring Joint Computer Conference. 287-301. To quote a little: "By precision clamping, the RMS level of binary noise can be closely controlled, but the non-stationarity of the circuits used to obtain electrical noise, even form stationary mechanism such an a radio-active source, still create problems and expense. For example, the 80 Kc random-telegraph wave generator .... required a fairly sophisticated and not completely satisfactory count-rate control loop. In the design of University of Arizona's new ASTRAC II iterative differential analyzer ... it was decided to abandon analog noise generation completely. Instead, the machine will employ a digital shift-register sequence generator ..." If you would like to investigate recent high-quality theoretical work on this matter, see the paper: "Generating Quasi-random Sequences from Semi-random Sources", Miklos Santha & Umesh V. Vazirani, Journal of Computer and System Sciences, Vol 33, No 1, August 1986, 75-87. They propose a clever method to eliminate the correlations in analog sources. Help stamp out scientific urban myths! Albert Boulanger aboulanger@bbn.com BBN Labs