[linux-audio-dev] next power of two

[Hannes Guddat]

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 at music.columbia.edu
> [mailto:linux-audio-dev-admin at music.columbia.edu]On Behalf Of
> Maarten de
> Boer
> Sent: Mittwoch, 17. September 2003 14:22
> To: linux-audio-dev at 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;
>          }
>
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