Re: sin() optimization on PowerPC and Intel
Re: sin() optimization on PowerPC and Intel
- Subject: Re: sin() optimization on PowerPC and Intel
- From: Bob Lang <email@hidden>
- Date: Tue, 27 Jun 2006 15:38:35 +0100
Hi
If you're looking for fast execution speed then I'd be tempted to set
up a large array and use it to store pre-computed sine values. This
converts each calculation into a simple and fast look up operation.
Of course, you only need to store one quarter of the cycle as the
remaining three quarters can be easily obtained from the stored first
quarter.
If you hold (say) 900 separate points, then you can store each sample
to a precision of 0.1 degree, which may already be sufficiently
accurate for your application. Obviously, you can get better
accuracy by using a bigger array and/or using a simple linear
interpolation technique on two adjacent samples.
Bob
--
On 26 Jun 2006, at 16:37, Artemiy Pavlov wrote:
Hello all!
I have the following problem. XCode 2.2, Mac OS 10.4.6 on Intel.
I created a sin() function replacement using four first members of
the Taylor series - works perfectly like the standard sin() (the
thing is that I need a very pure sine for FM purposes, so other
models do not work ear-wise).
But the thing is that it doesn't work any faster than the standard
sin() function... It's not optimized with assembly language, but
anyway has no division operations and all coefficients are pre-
computed. I heard that on Intels the sin() function is actually
implemented in CPU instructions, and that is why it works so fast.
Is this true?
So the question is - should I determine the CPU type for my
universal app and use sin() on Intel and custom sin() on PPC? If
so, are there any #define's available to be able to branch the code?
Thanks!
All the best,
Artemiy Pavlov
Sineshine http://sineshine.com
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