17 Sep
2003
17 Sep
'03
12:23 p.m.
Very interesting,
"in the name of all DSP programmers" - thanksalot!
Do you have any estimation how many cycles this would spend on a pentium? I
would have make a wild guess of about 16-21 cycles + call overhead (if not
inlined)..
Hannes
P.S. Maybe you have similar code for the "bitreverse" operation.. ? just
asking.. :)
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// Hannes Guddat
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-----Original Message-----
From: linux-audio-dev-admin(a)music.columbia.edu
[mailto:linux-audio-dev-admin@music.columbia.edu]On Behalf Of
Maarten de
Boer
Sent: Mittwoch, 17. September 2003 14:22
To: linux-audio-dev(a)music.columbia.edu
Subject: [linux-audio-dev] next power of two
Hi,
A colleague of mine found this very clever algoritm to calculate the
next power of two for a given number. It comes from the
Prophecy SDK for
3d game development
http://www.twilight3d.com/modules.php?op=modload&name=Download
s&file=index
Since this is a kind of thing often needed in audio
processing, I wanted
to share it with you. I certainly can not think of a faster (or more
elegant) way of doing it.
Maarten
//////
/// Returns the closest power-of-two number greater or equal
/// to n for the given (unsigned) integer n.
/// Will return 0 when n = 0 and 1 when n = 1.
//////
inline uint32_t nextPowerOfTwo(uint32_t n)
{
--n;
n |= n >> 16;
n |= n >> 8;
n |= n >> 4;
n |= n >> 2;
n |= n >> 1;
++n;
return n;
}