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From: Geert Bosch <geert@gonzo.sun3.iaf.nl>
Subject: Re: fixed point vs floating point
Date: 1997/11/23
Message-ID: <65846t$4vq$1@gonzo.sun3.iaf.nl>#1/1
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References: <mheaney-ya023680002211970739180001@news.ni.net>
Distribution: inet
Organization: La Calandre Infortunee
Newsgroups: comp.lang.ada,sci.math.num-analysis
Date: 1997-11-23T00:00:00+00:00
List-Id: <comp.lang.ada>


Matthew Heaney <mheaney@ni.net> wrote:

   Anyway, I'll accept that fixed point operations are slower, but the
   question remains: Why do most programmers insist on using floating point
   when a fixed point better models the abstraction?  Is the reason solely
   based on efficiency?

   By the way, are there off-the-shelf subprograms (in Ada preferably, but I'd
   take any language) for computing the elementary functions (sin, cos, etc)
   of a fixed point angle?


Maybe your second questions answers the first. It is really useless to
try hard to calculate a sinus using integer arithmetic when you have a
perfectly fine and very fast, well tested floating-point unit in your
computer that can calculate the sinus with a delta smaller than
0.000000000000001 probably.

Converting a fixed point value to fpt, issue the sinus instruction
and convert it back is much faster than even thinking about doing it in
fixed point. ;-)

Regards,
   Geert