Hi,
On Tue, 17 Feb 2009, John Tapsell wrote:
> 2009/2/17 Johannes Schindelin <Johannes.Schindelin@xxxxxx>:
>
> > 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;
> }
That assumes that your floats are IEEE floats, right?
Ciao,
Dscho
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