linuxaudio.org

On Saturday 01 May 2010, at 20.57.36, "Tim E. Real"

wrote:

[...]

quoted text
> I used to be fanatical about floating point (remember the co-processor

> days?) But I've grown to dislike it.

> Bankers won't use it for calculations.

> (Have you ever been stung by extra or missing pennies using a 'NUMBER'

>  database field instead of a 'BCD' field? I have.)

>

> So why do we use floating point for scientific and audio work?

Dynamic range, performance and ease of use. (However, as most FPUs - apart

from SIMD implementations that generally don't have denormals at all - lack a

simple switch to disable denormals, the last point is pretty much eliminated,

I think...)
> Considering audio can have really small values, does it not lead to errors

quoted text
>  upon summation of signals?

Yes, and no. If you add values in the same general order of magnitude, it's

pretty much like adding integers. If you add a very small value to a very

large one, and the difference is so large that the mantissas don't overlap,

nothing happens! >:-)
> Why do we not use some sort of fixed-point computations?
I do, sometimes. ;-) However, it's a PITA, and I do it only when the code is

supposed to scale to hardware with slow FPUs or no FPUs at all. I suspect

floating point implementations would run faster on current PC/workstation CPUs

- but then again, *correct* (ie denormal handling) code may not...! I'm not

sure.
--

//David Olofson - Developer, Artist, Open Source Advocate
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