Messages in this thread | | | Date | Wed, 20 Aug 2008 09:29:28 -0700 | From | "Ray Lee" <> | Subject | Re: VolanoMark regression with 2.6.27-rc1 |
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On Wed, Aug 20, 2008 at 8:10 AM, Nick Piggin <nickpiggin@yahoo.com.au> wrote: > On Thursday 21 August 2008 00:33, Peter Zijlstra wrote: >> On Wed, 2008-08-20 at 18:32 +0400, adobriyan@gmail.com wrote: >> > On Wed, Aug 20, 2008 at 03:32:17PM +0200, Peter Zijlstra wrote: > >> > > +#define avg(x, y) ({ \ >> > > + typeof(x) _avg1 = ((x)+1)/2; \ >> > > + typeof(x) _avg2 = ((y)+1)/2; \ >> > >> > ITYM, typeof(y) >> >> you thought right, I did mean that :-) >> >> > > + (void) (&_avg1 == &_avg2); \ >> > > + _avg1 + _avg2; }) > > I don't think this implementation of avg should go in kernel.h? > > It gives an average of 1 and 1 to be 2, 3 and 3 is 4, 1 and 3 is > 3 etc. > > Maybe it is reasonable for very high numbers that would overflow > if added first, but it doesn't seem reasonable for a generic > averaging function.
The usual way of averaging numbers that may be large is
#define avg(x, y) ({ \ typeof(x) _x = (x); \ typeof(x) _y = (y); \ (void) (&_x == &_y); \ _x + (_y - _x)/2; })
...which also works for small and negative numbers.
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