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Luigi October 18, 2012 07:03

PC doesn't work fast
I use ansys cfx 13 for CFD simulations and I have found that a pc is less fast as I expected.
During a simulation (carried out by Ansys CFX Solver) a pc with 8 processors (2 quad core) is as fast as another pc with only 4 processors (1 quad core).
The features of the former are:
OS windows 7 ultimate
2 quad core Intel Xeon E5430
Graphics card NVIDIA quadro nvs 290

Is there an explanation? Can I improve performance of this pc?

wyldckat October 18, 2012 17:51

Quick questions:
  1. Do both machines have the same CPU models? Namely "Intel Xeon E5430"?
  2. And do both have the same RAM size and speed?

Luigi October 19, 2012 05:35

The pc with fewer processors has the following characteristics:

intel core 2 quad CPU Q6600 @2.40 GHz, RAM 8 GB

evcelica October 19, 2012 13:45

Dumb question but....Are you actually using all 8 processors (are you running parallel or serial)?

Luigi October 22, 2012 06:58

Your question is much dumber...
It is obvious that i run the simulations in parallel with all 8 processors

wyldckat October 22, 2012 08:52

You didn't mention the RAM speed, which might be the main reason for the large difference in performance.

But assuming the speed is the same... here are other possible reasons:
  • The type of simulation you're running might not scale very well.
  • Not enough mesh points/cells to justify so many cores.
  • There could be a problem with the MPI library not properly distributing the threads to each core, making the performance drop considerably.
    There was a thread about this sometime ago... here we go: - problem is that thread was for Linux not Windows...
  • It could also be a problem with improper configuration of the BIOS of the machine, at least for this kind of simulation. This is addressed in the link above.

Last but not least, maybe it would be a good idea for you to contact your support for ANSYS, since this could be a specific problem that they know the solution for.
Another possibility is to ask in the dedicated thread for CFX:

evcelica October 23, 2012 16:24


Originally Posted by Luigi (Post 387867)
Your question is much dumber...
It is obvious that i run the simulations in parallel with all 8 processors

I was referring to my question being dumb, not yours. That's a real good way to get help with your system that obviously has some problems, good luck with it!

scipy November 3, 2012 06:22


Originally Posted by JohnK (Post 389960)
You can use Disk clean up, Disk dig-fragment, and event delete option. it is primary solution. If any bad sector in hdd then you may have to change hdd.

LOL! Great one. :D

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