Re: highest bit, statically determined

[Georg Bauhaus <rm.dash-bauhaus@futureapps.de>]

On 03.10.12 20:54, Georg Bauhaus wrote:
> <kalvink65@gmail.com> wrote:
>> How about binary search algorithm with constant execution time:
>>
>> Binary_Search_Highest_Bit_In_Octet_2012 : constant :=
>>        (if N > (2**4)-1 then -- determine upper or lower nibble
>>            -- upper nibble
>>            if N > (2**6)-1
>>              -- bits 7 and 6
>>              if N > (2**7)-1 then
>>
>
> Isn't this about the same as the recursive one?
> (It uses Boolean'Pos around the third if.)

> Also, I don't think its complexity is constant,

Ouch. I have thought again, it has constant execution time.
For the recursive one, the above one, and the one using a table,
respectively, I get, in seconds:

1.62, 1.57, 0.95