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From: earleh@eleazar.dartmouth.edu (Earle R. Horton)
Newsgroups: comp.sys.mac.programmer
Subject: Re: How to Cosine
Message-ID: <16306@dartvax.Dartmouth.EDU>
Date: 23 Oct 89 20:00:40 GMT
References: <2157@hudson.acc.virginia.edu> <4831@internal.Apple.COM>
Sender: news@dartvax.Dartmouth.EDU
Reply-To: earleh@eleazar.dartmouth.edu (Earle R. Horton)
Organization: Thayer School of Engineering
Lines: 22

In article <4831@internal.Apple.COM> chewy@apple.com (Paul Snively) writes:
...
>The reason for this is that SANE isn't as stupid as people think; since 
>ALL Mac IIs come with an FPU, SANE uses it, so you're pretty close to the 
>hardware when you use SANE on a Mac II.

I measure a 100 times speed increase on a Mac II using the MC68881
over SANE, with a trig-intensive application that uses doubles (64
bits) for the primary data storage type.  SANE does not use the
MC6888[12] for transcendental functions such as sine and cosine, but
it does offer 1 bit more accuracy than the FPU.  You take your pick, 1
bit more accuracy out of 80, or 100-fold speed increase.  The switches
to turn on the FPU from MPW C are -mc68881, -elems881, and -x149.  Use
the whole set.

The Aztec C floating point library (software) is less accurate than
SANE, but 2-3 times faster in my experience.  This is a software
solution that does not use an FPU at all.

No one is saying SANE is stupid, but it is slow.

Earle R. Horton