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From: nather@ut-sally.UUCP (Ed Nather)
Newsgroups: net.arch
Subject: Re: Floating point performance
Message-ID: <6028@ut-sally.UUCP>
Date: Fri, 17-Oct-86 12:28:57 EDT
Article-I.D.: ut-sally.6028
Posted: Fri Oct 17 12:28:57 1986
Date-Received: Fri, 17-Oct-86 22:56:04 EDT
References: <340@euroies.UUCP> <1989@videovax.UUCP> <722@mips.UUCP> <725@mips.UUCP>
Organization: U. Texas CS Dept., Austin, Texas
Lines: 32
Summary: Is this crazy?

When I first started messing with computers (longer ago than I like to
remember) I was discouraged to learn they could not handle numbers as
long as I sometimes needed.  Then I learned about floating point -- as
a way to get very large numbers into registers (and memory cells) of
limited length.  It sounded great until I learned that you give up
something when you do things that way --simple operations become much
more complex (and slower) using standard hardware.  Also, the aphorism
about using a lot of floating operations was brought home to me:
"Using floating point is like moving piles of sand around.  Every time
you move one you lose a little sand, and pick up a little dirt."

Has hardware technology progressed to the point where we might want to
consider making a VERY LARGE integer machine -- with integers long
enough so floating point operations would be unnecessary?  I'm not
sure how long they would have to be, but 512 bits sounds about right
to start with.  This would allow integers to have values up to about
10E150 or so, large enough for Avagadro's number or, with suitable
scaling, Planck's constant.  It would allow rapid integer operations
in place of floating point operations.  If you could add two 512-bit
integers in a couple of clock cycles, it should be pretty fast.

I guess this would be a somewhat different way of doing parallel
operations rather than serial ones.

Is this crazy?


-- 
Ed Nather
Astronomy Dept, U of Texas @ Austin
{allegra,ihnp4}!{noao,ut-sally}!utastro!nather
nather@astro.AS.UTEXAS.EDU