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Date:      Sun, 05 Dec 2010 16:00:32 -0800
From:      Julian Elischer <julian@freebsd.org>
To:        Steve Kargl <sgk@troutmask.apl.washington.edu>
Cc:        freebsd-current@freebsd.org
Subject:   Re: Process accounting/timing has broken recently
Message-ID:  <4CFC27A0.8000406@freebsd.org>
In-Reply-To: <20101205231829.GA68156@troutmask.apl.washington.edu>
References:  <20101205231829.GA68156@troutmask.apl.washington.edu>

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On 12/5/10 3:18 PM, Steve Kargl wrote:
> Sometime in the last 7-10 days, some one made a
> change that has broken process accounting/timing.
>
> laptop:kargl[42] foreach i ( 0 1 2 3 4 5 6 7 8 9 )
> foreach? time ./testf
> foreach? end
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         69.55 real        38.39 user        30.94 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         68.82 real        40.95 user        27.60 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         69.14 real        38.90 user        30.02 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         68.79 real        40.59 user        27.99 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         68.93 real        39.76 user        28.96 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         68.71 real        41.21 user        27.29 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         69.05 real        39.68 user        29.15 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         68.99 real        39.98 user        28.80 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         69.02 real        39.64 user        29.16 sys
> Max ULP: 0.501607 for x in [-18.000000:88.709999] with dx = 1.067100e-04
>         69.38 real        37.49 user        31.67 sys
>
> testf is a numerically intensive program that tests the
> accuracy of expf() in a tight loop.  User time varies
> by ~3 seconds on my lightly loaded 2 GHz core2 duo processor.
> I'm fairly certain that the code does not suddenly grow/loose
> 6 GFLOP of operations.
>
I know it's a lot to ask but it may be something that you can help 
with if you
had the time to triangulate in on the change that did it..
I presume that since you are an "old hand" you can check out sources 
at different revisions..




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