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From: john@x.UUCP (John Woods)
Newsgroups: net.crypt
Subject: Re: Re: Why no hardware random numbers?
Message-ID: <458@x.UUCP>
Date: Thu, 4-Apr-85 12:44:59 EST
Article-I.D.: x.458
Posted: Thu Apr  4 12:44:59 1985
Date-Received: Sun, 7-Apr-85 09:33:16 EST
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Organization: Charles River Data Systems, Framingham MA
Lines: 48

> > seems silly to you, check out the Table of 10,000 Random Digits in your
> > Rubber Bible (you *do* have the CRC Handbook of Mathmatics, don't you?).
> 
> to get lists of seeds.)  The same goes for using disk to read a random
> number list from.  The disk is a bit faster but not quite fast enough.
> 

I suppose I should have put a smiley on my CRC Handbook comment, I didn't
intend it to be a serious suggestion for a Monte Carlo simulation (after
all, it doesn't take long to go through 10,000 digits).  However, the
statement "The disk is a bit faster but not quite fast enough" is not
necessarily always true.  Consider the following C code:

	int fd;

	main() {
		int i,t;

		fd = open("randoms",0);

		for (i = 0; i < 50000; i++)
			Rand();			/* or just "rand()" */
		rand();
	}

	int buf[5000], nb;

	Rand() {
		if (nb == 0)
			nb = read(fd,buf,sizeof buf) >> 2;
		return buf[--nb];
	}

Thanks to the `huge' buffer I use (20Kb on my 68000), it turns out that this
program runs marginally faster using the disk table than when using the
"rand()" function directly.  OBVIOUSLY, your mileage may vary, but if your
system has good disk throughput and a computationally expensive rand(), then
you will likely see similar results, if you can afford a big buffer.  It will
also help if you don't mind having several megabytes of random data on your
disk (but if you have netnews...).

@Begin[ :-) ] By the way, back in college, we discovered that the Rubber
Bible bounces, when dropped on an appropriate carpet. @END[ :-) ]
-- 
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA

You can't spell "vile" without "vi".