[Numpy-discussion] Different results from repeated calculation

Robert Kern robert.kern at gmail.com
Mon Jan 29 15:47:27 CST 2007


Keith Goodman wrote:
> Here's a unit test for the problem. I am distributing it in hopes of
> raising awareness of the problem. (What color should I make the
> Repeatability Wristbands?)
> 
> I am sure others are having this problem without even knowing it.

Another datapoint using atlas3-base on Ubuntu AMD-64. Looking at the source
package, I think it sets ISAEXT="sse2" for AMD-64 when building.


rkern at rkernx2:~$ python repeat_test.py
repeatability #1 ... ok
repeatability #2 ... ok
repeatability #3 ... ok

----------------------------------------------------------------------
Ran 3 tests in 0.043s

OK
rkern at rkernx2:~$ uname -a
Linux rkernx2 2.6.17-10-generic #2 SMP Fri Oct 13 15:34:39 UTC 2006 x86_64 GNU/Linux
rkern at rkernx2:~$ cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 43
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
stepping        : 1
cpu MHz         : 2211.346
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext
3dnow up pni lahf_lm cmp_legacy
bogomips        : 4426.03
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 43
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
stepping        : 1
cpu MHz         : 2211.346
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext
3dnow up pni lahf_lm cmp_legacy
bogomips        : 4423.03
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp


-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco


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