Ansys on 2 x Dual Core Machine? 1

[richg1]

Hi,

Does anyone have any suggestions for getting Ansys to fully utilise all the processing power of a 2 x Dual Core machine (4 x Xeon E5335's).

In Design Modeller it only ever seems to use 25% and in Simulation 50%.

I think this may be a limitation of the licensing/software. But I was wondering if anyone had tried to lump the processers together so windows only shows them as one processor and hopefully tricks Ansys into using all the processing power available.

Hope that makes sense...Rich

 

[Stringmaker]

Ansys is only multi-threaded for the solution portion of the analysis. You can specify the number of processors in the product launcher or using the /CONFIG,nproc, command if you're still running v10. V11 and after only allow for the use of 2 processors without special licensing unforunately. Hence if I were building a new computer today I would care more about the clock speed than the # of cores in the system.

I've never seen design modeler utilze more than one processor for any process.

Best,
-Brian

 

[richg1]

I do remember reading about that, thanks for the info.

There is possibly a work around as I just got off the phone with Intel tech support and there supposedly is an advanced bios setting which allows you to turn off the multi-core architecture and treat the entire cpu as one core.

If anyone else has tried this I would be interested to get some feedback. It's pretty ridiculous that the software limits the use of all available processing power.

Will feedback soon...

Cheers...

 

[richg1]

Back again...

I switched the multi-core option off in the BIOS. Seemed to work. Unfortunately it still shows 2 cores - a function of an old bios but Design Modeller ran up to 50% of CPU rather the 25% usage it was showing with the quad core split.

Now limited by file I/O speed. If anyone else has tested this out please share your findings...

Cheers

 

[cbrn]

Hi,
1- of course it shows 2 processors if that's what is physically installed. "Cores" are a trick but physical processors are not. You can NOT combine two physical processors as being seen as only one by the O.S. However, having reduced to two processors you can now allow Ansys to take full advantage of them, for the processes which really are multi-proc-ready, without paying for the multi-proc license.
2- file swapping: in my experience, best performance is with SCSI subsystems. It doesn't matter if you have very fast SATA or things like that: The latest SCSI subsystems do are lightyears ahead. The fastest HD even nowadays are designed for SCSI subsystems. If you are already lucky enough to have the fastest possible SCSI system, then...
2a- expand RAM as much as you can (but max 3GB on Win32 systems, included Vista)
2b- use, if it's not already so, the /3GB switch in the "boot.ini" (only for Windows systems)
2c- consider using a 64bits architecture, and return to point 2a...
However, for many tasks ANSYS does write "a lot" on disk, independently from the RAM quantity. And if you have a 2GB result file, it will remain long to write even with 32GB RAM...

Regards

 

[Stringmaker]

Rich,
Which BIOS option allowed you to map both cores into one processor as seen by the OS? I have an AMD based workstation and don't have the parallel licensing option with Ansys. Perhaps I have this option as well in my system and just don't know about it yet...

Thanks,
-Brian

 

[richg1]

Brian,

The BIOS setting on our machine was under
Advanced > Advanced Processor Options > Core-Multi Processing.

Although I can't say that we noticed a vast improvement. As cbrn pointed out the disk read/write times are a limiting factor for big analyses with big result files. Our machine does have a raid mirror which I think is affecting our runtime speeds.

Cheers, Rich

 

[Stringmaker]

Thanks Rich. I'm not sure if AMD architecture has the same options for the BIOS. I have 16 GB of memory and have seen Ansys use up to 11 GB so my processors stay fully utilized. The only time Ansys writes to disk is when a load step finishes it writes the *.esav, *.emat, etc. All of the temporary files such as the *.LNXX are there but contain no data. I'd advise you to look into something 64-bit and with as much memory as you can cram in there. Memory is so dirt cheap anymore than the cost savings vs. time savings you see should equalize out in a matter of no time at all.