2009/2/17 Johannes Schindelin <Johannes.Schindelin@xxxxxx>:
> Hi,
>
> On Tue, 17 Feb 2009, Christian Couder wrote:
>
>> +static int estimate_bisect_steps(int all)
>> +{
>> + int log2 = 0;
>> + int left = (all >> 1) - 1;
>> +
>> + if (left <= 0)
>> + return 0;
>> +
>> + do {
>> + left = left >> 1;
>> + log2++;
>> + } while (left);
>> +
>> + return log2;
>> +}
>
> How about this instead, calling it from cmd_rev_list directly?
>
> static int log2(int n)
> {
> int log2;
>
> for (log2 = 0; n > 1; log2++)
> n >>= 1;
>
> return log2;
> }
This would work, if you want a non-iterative solution
unsigned int log2_integer_approximate(unsigned int n){
*((float*)&n) = (float)n;
return ((n & (~((1<<23) - 1))) >> 23) - 127;
}
(It's correct up to 2^25, then it's off by 1 for a few.)
> Ciao,
> Dscho
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