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Old   July 15, 2005, 16:47
Default Fluent on dual processor machine
  #1
Razvan
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Dear Fluent users.

My problem is of tehnical nature and it might not have any connection with the program itself. I completed today my dual processor machine:

2*Opteron 246 Tyan Tiger K8W 4 GB Corsair PC3200

To be more precise, I bought the 2nd processor. I installed WinXP x86-64 Professional Edition and Fluent 6.2.16 and went to bechmarking. Actually, I have a personal benchmark, a Rotor37 I calculated some time ago, with a 820.000 elements structured mesh.

On single CPU configuration I got 55 seconds/iteration.

Now comes the surprise: on dual CPU, SINGLE process I get 67 seconds/iteration !!! I couldn't belive my eyes! And that's not all: on PARALLEL processes I barely could achieve 40 seconds/iteration after testing several partitioning methods.

For those who don't know Tyan Tiger K8W, it is a SHARED memory board. Could this be the reason for such a poor performance? All reviews I ever read about this mainboard revealed a slight performance drop in comparison with DISTRIBUTED memory boards, but far smaller than what I am experiencing here!

I mention to have a strong background in serial Fluent, so I am pretty sure I made no mistake in setting up the case.

So, what I'm asking you is: have you ever experienced something similar, or even you may have an identic mainboard or a pretty much same configuration and can enlight me about this? Because I am quite desperate thinking that I invested 3000 $ in a machine which is only a "fart" better than a single CPU 1000 $ machine !!!

Appreciate any help.

Razvan.
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Old   July 16, 2005, 06:28
Default Re: Fluent on dual processor machine
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Jim Clancy
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If you use Linux, situation might be better.
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Old   July 16, 2005, 07:45
Default Re: Fluent on dual processor machine
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Razvan
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That's what I keep saying to myself.

I made some interesting tests lately: Sciencemark 2, 32bit and 64bit versions. What I immediately noticed was:

- some tests revealed good improvement in 64bit version, some extraordinary improvement(for example, "molecular dynamics" test results: 76 seconds/32bit, 28 seconds/64bit !!!)

- CPU utilization 100% all the time in 64bit version (it was an interesting thing to notice that 32bit Fluent is not fully utilizing the 2 CPUs)

You may be right, I should change track to 64bit Linux + 64bit Fluent.

Thanks a lot! Razvan
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Old   July 19, 2005, 11:13
Default Re: Fluent on dual processor machine
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Luke
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Try 32-bit Windows XP Professional. Win x64 can run only native 64-bit code, for 32-bit programs(like Fluent 6.2.16) it uses WOW32 emulator.
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