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johannes.tophoj December 15, 2011 03:39

The gain from additional multi-core processing power

I work in a small consulting company where we want to try OpenFOAM for incompressible transient analysis on unstructured grids. The extent of the simulations is to be determined and we further wish to 'feel our way there' with OpenFOAM.
We are looking for hardware that may serve as a starting point for testing OpenFOAM and possibly suffice for further simulations. But also hardware that is so relatively cheap that we may abandon it for something more powerful should the need arise.

I was considering something multi-socket & multi-core to get easily started. So only one OS needs to be set up and no network communication is required.
* One option I have found is 2x Xeon 5645 six core 2.4GHz and 48GB of RAM which is roughly 4700euro regardless of it being in a tower or blade.
* We could also go for 2x Xeon 5690 six core 3.46GHz at 7100euro.

The question is, how much will we gain from the additional processing power? As far as I have understood memory bandwidth may be the limiting factor. Or could the 12MB cache of each of the six cores be the bottle neck?

Any help is greatly appreciated


mgdenno December 28, 2011 20:39

My 2 cents. If you are just getting started with experience has been that it will run on just about anything. A decent desktop computer would work to get started if your cases aren't too large.

andyj December 29, 2011 01:27

OpenFoam is Linux based. It runs best on a 64 bit CPU.

The easiest way to get up and running with OpenFoam is to download a complete Linux operating system, with OpenFoam already installed.
two free ones are :
Suse 11.4 based

Ubuntu 10.04 based

If you already have a quad core machine, either amd or intel, you could simply add another hard drive

Then install the Linux distro on that hard drive. SUSE has windows Dual boot capability built into it and easily dual boots with windows.

Your windows installation would remain untouched. You would choose which operating system to start at bootup.

The last openfoam version with a GUI was openfoam 1.4. OpenFoam requires some command line entries to start it with the more recent versions.

You need to have a working knowledge of Linux and the Linux command line. Most of the OpenFoam tutorials are based on 1.4 with the foamX gui.
However the newer versions are pretty easy to use, you just need to use the command line to start the program.

There are only 7 parts to a computer. You can build your own computer pretty cheap.Easy to do. The only thing that can go wrong is installing the cpu into the motherboard. but that is easy to get right if you read the directions.

The cheapest minimal system:
AM3+ motherboard USD $ 60, Quad core AMD 640 or 840 $70,better yet AMD X6 $145
8gb ram $50,4gb ram $30, hard drive $55, power supply $30 case $40,
DVD R/W $30, Linux OS $0.00. Add $150 for Intel parts if you want to use intel.

You could just use Amazons Cloud CFD service. $2.50 per hour for large cluster use.
And set up the problem on a single quad core computer. No need for expensive hardware, use Amazons.

With regards to your Xeon question, you can never have too much computing power.

johannes.tophoj December 29, 2011 14:15

Hi Matthew, Andy

Thank you for your replies. I ended up with dual six core Xeons (2.66GHz) as the step to 3.4GHz was large, economically speaking.

I am used to Linux so that part will be ok. I was thinking about som *buntu variant and I will take a look at CAELinux as you suggest.



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