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From: vu0310@bingvaxu.cc.binghamton.edu (R. Kym Horsell)
Newsgroups: comp.arch
Subject: Re: Killer Micro II
Message-ID: <3922@bingvaxu.cc.binghamton.edu>
Date: 31 Aug 90 15:18:39 GMT
References: <527@llnl.LLNL.GOV> <603@array.UUCP> <2482@l.cc.purdue.edu> <2868@inews.intel.com> <8442@fy.sei.cmu.edu>
Reply-To: vu0310@bingvaxu.cc.binghamton.edu.cc.binghamton.edu (R. Kym Horsell)
Organization: SUNY Binghamton, NY
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In article meissner@osf.org (Michael Meissner) writes:
\\\
>measurement only had 3-5 digits of accuracy. This means that any
>answer received cannot be more accurate than the input. Now in order
>to avoid round off error, you certainly need more digits internally,
>but IEEE double gives something 12-14 digits. One of the problems the
Unfortunately, ``round off'' error is not the real problem.
*Loss of significance* results when, for example, two positive FP numbers with
similar magnitude are subtracted. The occurence of same is not
always predictable and the ``quick fix'' is to use more precision.
Despite this, the cliche of failing to invert a 100 x 100 matrix
still holds fairly well, no matter what the precision (unless we
leave the realm of FP altogether for modular arithmetic, etc).
Another point, although many quantities derrived from the real world are not
known to high accuracy, this is certainly not true of some common physical
constants, e.g. Plank's constant or the speed of light.
-Kym Horsell