On 1/27/07, Stefan van der Walt
On Sat, Jan 27, 2007 at 03:11:58PM -0700, Charles R Harris wrote:
Does anyone else see this happening?
Yes,
test1: 0 differences test2: 51 differences test3: 0 differences
Oddly, the relative error is always the same:
98 z different 2.0494565872e-16 99 z different 2.0494565872e-16
Which is nearly the same as the double precision 2.2204460492503131e-16,
difference being due to the fact that the precision is defined relative to 1, and the error in the computation are in a number relatively larger (more bits set, but not yet 2).
So this looks like an error in the LSB of the floating number. Could be rounding, could be something not reset quite right. I'm thinking
the possibly
hardware at this time, maybe compiler.
Interesting! I don't see it on
Linux alpha 2.6.17-10-386 #2 Fri Oct 13 18:41:40 UTC 2006 i686 GNU/Linux vendor_id : AuthenticAMD model name : AMD Athlon(tm) XP 2400+ flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow up ts
but I do see it on
Linux voyager 2.6.17-10-generic #2 SMP Fri Oct 13 18:45:35 UTC 2006 i686 GNU/Linux processor : 0 vendor_id : GenuineIntel model name : Genuine Intel(R) CPU T2300 @ 1.66GHz processor : 1 vendor_id : GenuineIntel model name : Genuine Intel(R) CPU T2300 @ 1.66GHz flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc pni monitor vmx est tm2 xtpr
Both machines are running Ubuntu Edgy, exact same software versions.
Hmmm, and your problem machine is running smp linux. As is mine; fedora uses smp even on single processor machines these days. I think we could use more data here comparing OSX Linux (single, smp) Window Chuck