Re: from number to power of two

[Peter Dufault]

> It seems that all the solutions are too generic and slow. As I only have
> to check the numbers 0-32 (actually 1-32), a block of if statements is
> almost as fast as a table look up in 33 elements.

I doubt it - use the table for a small fixed size set then
use Warner's "(n) ? (1 << (ffs(n) - 1)) : 0".
The possible inline ffs is in machine/cpufunc.h

ffs() is fundamental to scheduling queues and cryptography and
should have attention paid to it.  As Warner said, it could be
a single instruction on some architectures.

Peter

-- 
Peter Dufault ([EMAIL PROTECTED])   Realtime development, Machine control,
HD Associates, Inc.               Safety critical systems, Agency approval


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