Performance question

[maheshh]

May not be the right forum to post, because the question is not about Ansys functionality -- but it is about performance.

I recently upgraded my system from a 2 processor to 4 processor Opterons which now support 64 bit computing. My question is, should I upgrade my OS from Windows Server 2000 (32-bit) to Windows Server 2003 Enterprise (64-bit)?

1) Will this significantly improve the computation time?
2) With this upgrade, I dont want my Ansys 7.1 to start crashing on me. Are there any issues with 7.1 and Server 2003 combo?
3) Should I also move to Ansys 10? Usually all the software upgrades are backward compatible, so my 7.1 models should work ok with version 10 am assuming. How is Ansys 10 better than Ansys 7.1?

Thanks in advance.
Mahesh

 

[Drej]

The standard ANSYS implicit solver can only use a single CPU -- no parallelisation -- so you can draw your own conclusions from this. ANSYS 10 is very different to 10, much better functionality and better elements and formulations, contact algorithms, easier contact setup and analysis, better non-linear tools, etc. etc. Lots of things. Upgrade to 10 if you can.


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[cbrn]

Hi,
I believe you will get benefits if you have a parall license, so that you can use special parall solvers (not for all analyses, anyway). You can also configure an "auto-cluster", i.e. a distributed network of processors which physically reside on the same machine but are seen as several different machines: this would be useful for batch run of multiple loadcases (even if setting up ANSYS and the required software in order to do this is anything but simple...).
64 bits is a must if you have problems of memory allocation, as, for performance, Ansys has not been recompiled for native 64 under Windows (Unix or Linux is another thing...).
For a server, 4 procs instead of 2 can be useful also if remote users run each a license of ANSYS and solve simultaneously on the server machine. For workstation use, instead, not more than 2 procs are recommended (this allows for interaction with other softwares while ANSYS is running, without performance loss).
A last thing: setting "NPROC" is a discussed matter, as you can see in other threads i this forum; apparently, it is still unclear if setting it to the total number of procs is beneficial or not; Ansys recommends not exceeding numprocs-1. Same thing as regards hyperthreading: some see benefits in deactivating it, others (like me) find better performance in letting it on and setting NPROC to the number of virtual processors: probably it depends also on other aspects of the workstation hardware.

Regards

 

[maheshh]

Thanks for the responses.

Right now I am on a workstation, and I have set the NPROC to 4, asking Ansys to use all the 4 processors. I have seen a marked improvement in the performance from when I was on the 2P machine. Although some part of solving a 150K node problem is also read-write operation. Since memory access speed is still the same, the total solve time has not improved by a factor of 2.

Drej,
You mentioned that Ansys 10 has a better contact algos, and also it is easier to setup a problem. I think I will upgrade today as I am currently working on a contact problem.

I am also talking to Ansys tech support about performance improvements by moving from a 32 bit to 64 bit OS on a Windows platform. I will post their response once I hear from them.

Regards,
Mahesh.