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Re: About the bits reserved for float variable [message #39498 is a reply to message #39497]

Fri, 21 May 2004 15:22

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article <MPG.1b17c91c4c958ba1989761@news.frii.com>,
David Fanning <davidf@dfanning.com> wrote:

> it this way, you can have fast or accurate, but you
> can't have both. That's about as much as I've ever
> needed to know using a computer. :-)

It used to be that integer arithmetic was faster than floating point,
but that is generally no longer the case. Just about all machines
that I know of can do integer or floating point ops in a single
clock cycle. Some cpus can do more than one op per clock cycle.
(That's what many of those millions of transistors on
modern cpus are used for.)

Additionally, many (but not all) architectures have double-precision
floating point hardware units. DP operations on those systems are as fast as
single precision. On many machines the only drawbacks to doing everything
in DP are: twice as much memory is required and twice as much file
space.

My rules of thumb:
Use integers for things you can count (i.e., no fractions).
Use doubles for "real numbers", unless memory is a problem.
Write files in single or double precision, as needed.

Ken Bowman

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[Message index]

		Re: About the bits reserved for float variable By: George N. White III on Sat, 22 May 2004 05:01
		Re: About the bits reserved for float variable By: Kenneth P. Bowman on Fri, 21 May 2004 15:22
		Re: About the bits reserved for float variable By: David Fanning on Fri, 21 May 2004 08:07
		Re: About the bits reserved for float variable By: James Kuyper on Fri, 21 May 2004 08:00
		Re: About the bits reserved for float variable By: Paul Van Delst[1] on Fri, 21 May 2004 07:44
		Re: About the bits reserved for float variable By: Chris Lee on Fri, 21 May 2004 07:36
		Re: About the bits reserved for float variable By: Nuno Oliveira on Tue, 25 May 2004 10:08

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