On 03 Mar 2007 03:31:52 +0100
Andi Kleen <[EMAIL PROTECTED]> wrote:
> Stephen Hemminger <[EMAIL PROTECTED]> writes:
>
> > Here is another way to handle the 64 bit divide case.
> > It allows full 64 bit divide by adding the support routine
> > GCC needs.
>
> Not supplying that was intentional by Linus so that people
> think twice (or more often) before they using such expensive
> operations. A plain / looks too innocent.
>
> Is it really needed by CUBIC anyways? It uses it for getting
> the cubic root, but the algorithm recommended by Hacker's Delight
> (great book) doesn't use any divisions at all. Probably better
> to use a better algorithm without divisions.
>
I tried the code from Hacker's Delight.
It is cool, but performance is CPU (and data) dependent:
Average # of usecs per operation:
Hacker Newton
Pentium 3 68.6 < 90.4
T2050 98.6 > 92.0
U1400 450 > 415
Xeon 70 < 90
Xeon (newer) 71 < 78
EM64T 21.8 < 24.6
AMD64 23.4 < 32.0
It might be worth the change for code size reduction though.
--
Stephen Hemminger <[EMAIL PROTECTED]>
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