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Re: Wow!


On Tue, 2007-07-03 at 13:07 +0200, Richard Guenther wrote:
> On 7/3/07, Daniel Berlin <dberlin@dberlin.org> wrote:
> > On 7/2/07, Uros Bizjak <ubizjak@gmail.com> wrote:
> > > Daniel Berlin wrote:
> > > > I'm curious if it was the pre/fre changes.  can you try -fno-tree-pre
> > > > and -fno-tree-fre and see if it slows down again?
> > > Adding -fno-tree-pre slows aermod back to 33.942s. Nice optimization. ;)
> > Thanks.
> > (You really should thank richard guenther and steven bosscher, who
> > continually beat me up till i finished it :P)
> >
> 
> Unfortunately, this "improvement" is a miscompare:
> 
> > Value= 2190.9357900     Target= 2191.1145000     Tolerance=0.10000000000E-02
> FAIL <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> > Value= 34310.421880     Target= 34310.421880     Tolerance=0.30000000000E-01
> > Value= 4260.5888700     Target= 4260.9716800     Tolerance=0.50000000000E-01
> FAIL <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> > Value= 37093.921880     Target= 37094.375000     Tolerance=0.20000000000E-01
> FAIL <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> > Value= 7924.6811500     Target= 7924.8842800     Tolerance=0.30000000000E-01
> FAIL <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> > Value= 37093.921880     Target= 37094.375000     Tolerance= 1.0000000000
> 
> aermod FAILED    4 fails and    2 passes
Having been down this path so many times -- any time a benchmark shows
a big improvement, my first reaction is that something has been mis-
compiled.  If not, then I worry that it's just some ugly secondary
cache effect from variables moving around on the stack or something
similar.  Only once I can convince myself that neither of those is the
case do I get excited about the improvement.

Perhaps I've become somewhat jaded through the years :-)

Jeff

> 
> Richard.


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