From:	Arash <ei39594 AT ios DOT chalmers DOT se>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Fixed Point (Optimization)
Date:	Sat, 04 Jan 1997 19:49:13 +0100
Organization:	Chalmers University of Technology
Lines:	34
Message-ID:	<32CEA629.1650@ios.chalmers.se>
References:	<32cd6b2c DOT 4726585 AT nntp DOT southeast DOT net>
NNTP-Posting-Host:	sv320110.ios.chalmers.se
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Murray Stokely wrote:
> 
>      Is Fixed-Point math still a neccesity for today's computers with
> all their built it FPU's, etc?  How much faster can it be?  Anyway,
> this is the same code procedure from our long thread on optimization;
> I've recently come back to it, because I still see room for
> improvement.  What can be done to it.  Fixed point?  Lookup tables?....
> Murray Stokely ( murray AT southeast DOT net )
> http://www.cdrom.com/pub/artpacks

Run Quake on a 486 and you will get you answer (Quake uses some fpu instructions)


BTW, some friend of mine suggests that you should use Tyler-polynoms insted, but don't ask me what it is....
I would NOT use sqrt() at all, you can't use lookup-tables for sqrt() but you can do a lot of other stuffs with it.

and i think that this is the part that slows down most (an fpu instruction inside a loop???) :
....
 } else {
       z=round(sqrt(r2-x2-y2));
....


Please let me know if i'm wrong!


-- Arash
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