[phobos] phobos commit, revision 2186

[Lars Tandle Kyllingstad]

Intel Core 2 Duo:  Pass

-Lars



On Sun, 2010-11-21 at 12:18 -0500, David Simcha wrote:
> Can others on this mailing list please submit info about their CPUs 
> (manufacturer and core type) and whether the unit tests pass?  My 
> working hypothesis (mostly because I can't think of anything else that's 
> at all plausible) is that this discrepancy is somehow hardware-related.  
> I'll start and give an example of what I'm looking for:
> 
> Intel Penryn:  Pass
> AMD Brisbane:  Fail
> 
> On 11/21/2010 1:19 AM, Don Clugston wrote:
> > On 21 November 2010 05:48, David Simcha<dsimcha at gmail.com>  wrote:
> >> More research into this issue:  I compiled the unittest.exe executable on my
> >> main (desktop) computer, ran it under my primary OS (Win7 64) and it
> >> failed..  I then ran the exact same executable (no recompile) on my Linux
> >> Partition (Ubuntu 10.10 64) using Wine and it failed.
> >>
> >> I then ran the exact same executable on my laptop on my primary OS (also
> >> Win7 64) and it passed.  I ran it on my laptop's Linux partition under Wine
> >> (Ubuntu 10.10 32) and it passed.
> >>
> >> The only difference between the two systems that might account for this is
> >> that the laptop has an Intel Penryn CPU, whereas the desktop as an AMD
> >> Brisbane CPU.  Does anyone know whether different x86 CPUs can produce
> >> subtly different floating point results when executing the exact same code?
> >> Alternatively, is it possible that some processor-specific optimizations to
> >> some function getting called by Don's code could be causing slightly
> >> different results?
> > That's _very_ interesting. The code in question doesn't use the C
> > runtime at all.
> > If it's the same exe, then the difference can only lie in the CPU or
> > in the environment.
> > Eg, if it starts with 80-bit floats disabled.
> > But the fact that every other test passes on your system, makes that
> > seem unlikely.
> > Does the failing system have execution protection enabled?
> >
> > The only documented floating point difference between AMD and Intel
> > that I know of, is that AMD
> > raises the invalid exception when loading an 80-bit NaN, but Intel
> > doesn't. BTW I found that difference
> > myself, and added it to Wikipedia. That difference is not relevant here.
> >
> > If the CPU itself is responsible for the difference, that's a CPU bug.
> > BTW this test was present in Tango for years, and nobody ever reported
> > this issue before.
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> >
> 
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