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From: djh@xipe.osc.edu (David Heisterberg)
Newsgroups: comp.lang.c
Subject: Re: Floating Point Arithmetic
Message-ID: <1143@sunc.osc.edu>
Date: 10 Nov 90 17:44:37 GMT
References: <14366@smoke.brl.mil> <14406@smoke.brl.mil> <232@smds.UUCP>
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In article <232@smds.UUCP> rh@smds.UUCP (Richard Harter) writes:
>                                               Situations where 32 bit
>precision does not suffice are usually either numerically poorly conditioned
>or inherently require high precision.  In these cases double precision
>is a dangerous nostrum -- one should do one's numerical analysis homework.

There is also the case of theoretical work, such as quantum chemistry,
for which all data is known exactly: in atomic units hbar = 1.0, qe = -1.0,
me = 1.0, etc.  It's not uncommon to "out do" others by calculating
energies that are less than 1 part in 10^6 lower than  previous values.
For such comparisons to have meaning in the face of a few large matrix
diagonalizations, double precision is a must.
--
David J. Heisterberg		djh@osc.edu		And you all know
The Ohio Supercomputer Center	djh@ohstpy.bitnet	security Is mortals'
Columbus, Ohio  43212		ohstpy::djh		chiefest enemy.