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<[email protected]> 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. > > _______________________________________________ > > phobos mailing list > > [email protected] > > http://lists.puremagic.com/mailman/listinfo/phobos > > > > _______________________________________________ > phobos mailing list > [email protected] > http://lists.puremagic.com/mailman/listinfo/phobos _______________________________________________ phobos mailing list [email protected] http://lists.puremagic.com/mailman/listinfo/phobos
