Floating Point Arithmetic

[David Heisterberg]

In article <232 at smds.UUCP> rh at 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 at osc.edu		And you all know
The Ohio Supercomputer Center	djh at ohstpy.bitnet	security Is mortals'
Columbus, Ohio  43212		ohstpy::djh		chiefest enemy.