Re: NaN slowdown with some processors

[Dmitri A. Sergatskov]

On Wed, Jun 4, 2008 at 1:11 AM, Olli Saarela <address@hidden> wrote:
> Hello,
>
> I'm planning to buy a new desktop machine, and since my computations
> utilize NaN values heavily, I'd like to know whether Intel Core 2
> processors suffer from the same slowdown with NaN values as Pentium. For
> details, see http://www.cygnus-software.com/papers/x86andinfinity.html
>
> If someone has Octave on a machine with a Core 2 processor, please run
> the following commands and tell the results. (Or a more detailed test
> from ftp://ftp.cygnus-software.com/pub/specialnumbers.zip)
>
>     a=zeros(300,300);tic;b=(1.0+a)*a;toc
>     a=zeros(300,300);tic;b=(NaN+a)*a;toc
>


octave:5> a=zeros(300,300);tic;b=(1.0+a)*a;toc
Elapsed time is 0.016305 seconds.
octave:6>     a=zeros(300,300);tic;b=(NaN+a)*a;toc
Elapsed time is 0.101054 seconds.
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Xeon(R) CPU            5130  @ 2.00GHz
stepping        : 6
cpu MHz         : 1994.998
cache size      : 4096 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor
ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm
bogomips        : 3992.39
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Xeon(R) CPU            5130  @ 2.00GHz
stepping        : 6
cpu MHz         : 1994.998
cache size      : 4096 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor
ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm
bogomips        : 3990.00
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

Dmitri.
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