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Re: Fast exponent and logarithm, given initial estimate
Posted:
Oct 19, 2004 10:55 PM
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> You also need to specify how accurate the log(x) and exp(x) must be -
> fastest methods that cut corners for speed are not necessarily as
> accurate.
I'd like it within 3 to 4 ulps of the Standard C library values for
exp and log.
The log estimate provided with Altivec hardware has absolute error of
1/32 (except |x - 1| < 1, go figure..., perhaps they used the formula
you gave), and the exponent estimate has relative error of 1/16,
except for integers where it is accurate.
Cheers,
Glen Low, Pixelglow Software
www.pixelglow.com
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