Did you profile your code and see where are you spending your time in
the code? What is your memory access pattern? What compiler/compiler
options are you using to compile your code?
Profile using Shark (profiling tool that comes with CHUD performance
tools) and see if you can determine why you are not seeing as much
scaling as you were expecting to see on the dual G5 system.
Yusuf
On Jan 22, 2004, at 3:45 PM, Sean C. Garrick wrote:
I've been doing some more benchmarking using two homegrown CFD codes,
this time with Opterons and PPC-970s (G5).
Here is a typical single processor result :
Small memory code (110 MB): Time Opteron / Time G5 = 2.3
Opteron: 85 seconds
G5: 36 seconds
Large memory code (450MB) Time Opteron / Time G5 = 1.9
Opteron: 454 seconds
G5: 237 seconds
While the G5 is faster, the Opteron seems to have a better memory
access/bandwidth.
Also, I ran a job one job on the G5 using 1 processor and another
using 2 processors. The speed-up was only 50%. I did the same thing on
the Opteron and the speed-up was 83%!!!
I'm not sure what type of board the Opteron was built on but this is
very surprising as Apple was touting its motherboard as having the
most bandwidth. I think the performance is quite poor and I'm
wondering its worth getting 2 CPUs per board or just go with one?
Any ideas?
Thanks,
Sean
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