On Sun, 2007-10-28 at 14:01 -0700, Joe Perches wrote:
> probably unsigned long should be u16.
Or not.
x86 u16 performs much worse than u32 (~ 50% worse)
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On Sun, 2007-10-28 at 21:18 +0100, Urs Thuermann wrote:
> I have written a short test program to show this and tested it on i686
> (gcc-4.2.2) and powerpc (gcc-3.4.5) without optimization and with -O6.
Thanks for that.
> BTW, shouldn't unsigned long be replaced by unsigned int to avoid
> 64-bit
Herbert Xu <[EMAIL PROTECTED]> writes:
> But your code differs significantly from Stephen's version.
> However, if it is correct it does look like a good improvement.
>
> So please write a simple test program. It can't that bad since
> there are only 65536 values to test :)
I think the code is
On Mon, 2007-10-22 at 20:30 -0700, Stephen Hemminger wrote:
> > Corrected fast code is:
> >
> > while (len--) {
> > sum += *data++;
> > sum <<= 1;
> > sum = (((sum & 0x1) >> 16) + sum) & 0x;
> > }
> >
> > At least it is corre
Joe Perches <[EMAIL PROTECTED]> wrote:
> On Mon, 2007-10-22 at 18:43 -0700, David Miller wrote:
>> Ok, but again did you test it?
>
> Nope. Stephen Hemminger did in 2003.
But your code differs significantly from Stephen's version.
However, if it is correct it does look like a good improvement.
On Mon, 22 Oct 2007 12:36:19 -0700
Joe Perches <[EMAIL PROTECTED]> wrote:
> It's a bit after 2.6.1 now...
>
> Removes unnecessary if, uses 16 bit rotate left.
> Performance improves ~30%
>
> Signed-off-by: Joe Perches <[EMAIL PROTECTED]>
>
> diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.
On Mon, 2007-10-22 at 17:35 -0700, David Miller wrote:
> Your code is rotating bit 15 down by one bit and bits 0-14 up by one
> bit.
Yes, a 16 bit rotate left.
There was a discussion a few years ago:
http://oss.sgi.com/archives/netdev/2003-10/msg00734.html
>From the spec:
Implementers of DDP sh
On Mon, 2007-10-22 at 18:43 -0700, David Miller wrote:
> Ok, but again did you test it?
Nope. Stephen Hemminger did in 2003.
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From: Joe Perches <[EMAIL PROTECTED]>
Date: Mon, 22 Oct 2007 18:36:28 -0700
> On Mon, 2007-10-22 at 17:35 -0700, David Miller wrote:
> > Your code is rotating bit 15 down by one bit and bits 0-14 up by one
> > bit.
>
> Yes, a 16 bit rotate left.
>
> There was a discussion a few years ago:
> http
From: Joe Perches <[EMAIL PROTECTED]>
Date: Mon, 22 Oct 2007 12:36:19 -0700
> It's a bit after 2.6.1 now...
>
> Removes unnecessary if, uses 16 bit rotate left.
> Performance improves ~30%
>
> Signed-off-by: Joe Perches <[EMAIL PROTECTED]>
I'm not sure your transformation is equivalent. Did yo
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