Message-ID: <32B5F465.1394@gbrmpa.gov.au>
Date: Tue, 17 Dec 1996 09:22:16 +0800
From: Leath Muller <leathm AT gbrmpa DOT gov DOT au>
Reply-To: leathm AT gbrmpa DOT gov DOT au
Organization: Great Barrier Reef Marine Park Authority
MIME-Version: 1.0
To: DJ Delorie <dj AT delorie DOT com>
CC: Kevin AT Quitt DOT net, djgpp AT delorie DOT com
Subject: Re: Is DJGPP that efficient?
References: <199612161349 DOT IAA01371 AT delorie DOT com>
Content-Type: text/plain; charset=us-ascii
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> It doesn't implement them completely.  Nearly all the transcendental
> functions require you to "massage" the data to get it into the range
> the fpu supports.  For example, sin(x) is only valid for small values
> of x; you must divide by 2PI and take the sin() of the remainder.
> That eats up a lot of cycles.

Ok... :)  I was gettin over a lot of the hurdles with the limitations
by precomputing them: loading the inbuilt Pi, mul by 2, fld1,
fdiv ST, ST(1), and store as _1on2PI. Its messy, but it works... :)
Mind you, as I only do texture mapping and gourard shading etc, I
don't really need to use sin, cos, sincos, etc, so my experience with
these is limited...I just played with them at one stage for fun...

Oh well, I spose 34 cycles for a 4x4 matrix multiply good enough
nowadays anyway... :)  And remember, it could be worse: we might
still be using external 386 FPU's... *GRIN*

Leathal.