On 1/27/07, Stefan van der Walt <[EMAIL PROTECTED]> wrote:
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, the > 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 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
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