Norman Gray wrote:
> Tim,
>
> On 2005 Aug 24 , at 20.04, Tim Jenness wrote:
>
>> My timings are
>>
>> Apele (2.7 GHz PPC 8GB):
>> no opt 36 s
>> -O2 30
>> -O3 30
>> -O3 -faltivec 30
>> -O3 -faltivec -mcpu=powerpc64 24
>> -O3 -faltivec -mcpu=powerpc64 -m64 12 *
>
>
> The timings on my laptop are:
>
> -O0
> real 4m21.834s
> user 1m27.934s
> sys 0m14.639s
>
> -O2
> real 1m38.204s
> user 0m58.125s
> sys 0m6.467s
>
> -O3
> real 1m5.366s
> user 0m56.284s
> sys 0m2.975s
>
> -O3 -faltivec
> real 1m3.961s
> user 0m56.280s
> sys 0m2.927s
>
> -O3 -maltivec -mcpu=powerpc
> real 2m21.231s
> user 0m58.241s
> sys 0m6.582s
>
>
> This is a 1.5GHz G4 with 1GB of memory, and appears to be roughly half
> the speed of Tim's 2.7GHz G5 (which is odd). Since it's a G4, the
> powerpc64 options don't work; it's nonetheless bizarre that adding
> -mcpu=powerpc actually slows things down, and matches just the -O2 one
> (am I misunderstanding what G4s are???). This is gcc 4.0.0.
>
> Is this actually telling us that the PowerPC memory bandwidth is poor?
> Or that gcc 3.x is ill-optimised for it. I'm hopeless at interpreting
> benchmarks.
>
> These are with the system unloaded. Apart from the -O0 one they're
> faster than or comparable with Steve's G5 -- since this is testing
> memory bandwidth, it doesn't make much sense to do it with other things
> swapping in and out, as Steve noted.
>
>> Looking on this page, the FPU of the G5 appears to be good, but the
>> other aspects are poor:
>>
>> http://www.tux.org/~mayer/linux/results2.html
>
>
> That might be overstating it.... That table appears to be ranked by
> INT performance (I thought PowerPCs were supposed to be wonderful for
> integer stuff).
>
> See you,
>
> Norman
>
>
Here are the G5 1.8GHz PPC idle results:
no opt 1m3.805s
-O2 0m44.355s
-O3 0m44.393s
-O3 -faltivec 0m44.349s
-O3 -faltivec -mcpu=powerpc64 0m17.346s
Steve.
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