Re: [PATCH] rev-list: estimate number of bisection step left

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Tue, 17 Feb 2009, John Tapsell wrote:

> 2009/2/17 Johannes Schindelin <Johannes.Schindelin@gmx.de>:
>
> > On Tue, 17 Feb 2009, John Tapsell wrote:
> >
> >> 2009/2/17 Johannes Schindelin <Johannes.Schindelin@gmx.de>:
> >>
> >> > 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?
> 
> Yeah.  Is it a bad assumption? Does git run on any system in which they 
> aren't?

Only when you are porting Git to embedded devices.

Don't moan: there exists a git-daemon for iPhone.  Oh, wait!  /me 
scribbles that down for the UGFWIINI contest.

Ciao,
Dscho