On Sat, Jan 29, 2011 at 12:07:12PM +0100, Philipp Überbacher wrote:
> Took me a while to figure out that libm is part of glibc :)
It isn't. But it lives in /lib, not /usr/lib
> > k = (int)(log2(x) + 1e-6)
>
> log2() suffers from the same problem? I somewhat dislike the idea of
> adding a constant.
Everything floating point 'suffers from the same problem'.
Even addition. (1/3.0 + 1/3.0 + 1/3.0 == 1.0) doesn't have
to result in true.
> > int m, k;
> > for (k = 0, m = 1; m < x; k++, m <<= 1);
> >
> > which will round up if x is not a power of 2.
>
> Neat. I thought about it myself yesterday but my ideas weren't exactly
> brilliant. One idea was to divide by 2, the other to use a small
> lookup table for powers of 2. I don't really know about efficiency, but
> I guess bit shifting is as efficient as it gets?
It's a single CPU cycle on most processors, and on some (e.g. ARM)
it can even be combined with other instructions.
Ciao,
-- FA There are three of them, and Alleline. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@email-addr-hidden http://lists.linuxaudio.org/listinfo/linux-audio-userReceived on Sat Jan 29 16:15:02 2011
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