Quad core processors

[gurmeet2003]

I am considering buying a workstation with with two quad core processors. I use ABAQUS software. Will it be equal to buying 8 single processors. Pleas give me your comments.

Thanks,

Gurmeet

 

[IRstuff]

Depends on what you're doing. In some cases, it'll be faster, in others, it'll be slower.

TTFN

FAQ731-376

 

[GregLocock]

Will you need 8 licenses?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[johnhors]

Yes, Abaqus can address all eight processors, just add "cpus=8" to the end of the job command line when launching Abaqus with the job=file_name command.

But as Greg hinted, you will need a bucket full of license tokens to be able to do this !! How many tokens do you have, currently use on jobs?

For your new workstation, I'd suggest going 64bit (with XP64 if using windows - NOT Vista !) and at least 8Gb of ram, so that solutions can be run without paging to disc.

 

[Jordonlaw]

The bus speed of quad core processors isn't currently as fast as the dual core alternatives. My benchmarks have shown that dual cores are still the way to go.

 

[gurmeet2003]

Thanks for your replies TTFN,Greg, Johnhours and Jordanlaw. I am looking at 32 GB RAM with 2 Intel 5460 quad core processors. Currently I have two single core AMD Opteron processors. I am currently using 6 tokens. I have a recent quote from ABAQUS. According to this for 4 cores I will need 8 tokens, and for 8 cores I will need 12 tokens. So if I go for 8 cores my annual lease price will double. In terms of pricing ABAQUS does not differentiate whether one uses an extra core or processor.

Our IT group only wants to support Windows. However my current workstation has SUSE Linux and I am very happy with ABAQUS on Linux. Does anyone have experience with ABAQUS on 64 bit windows? How would one compare performance of ABAQUS on Windows vs. Linux?

ABAQUS have also informed me that they also give extra tokens on monthly rate. I am leaning towards buying the computer with 8 cores, but lease only enough tokens for 4 cores (8 tokens). Whenever I have a bigger job, I can rent the extra tokens. One quad core processor costs about $1800.

Looking forward to your comments.

Thanks,
Gurmeet

 

[Jordonlaw]

"How would one compare performance of ABAQUS on Windows vs. Linux?"

You need to do this on the specific machine your interested in using. I did a benchmark (not Abaqus but non-linear FEA)that showed that Linux was faster than Win64 on dual core machines when both cores on a physical chipset were being used. Something to do with the bus speed on the chip maybe and why I would stay away from quad cores. Other bechmarks with other codes don't show the problem bwteen OSs.

Can you lease a machine with a buy option afterwards to test the performance They you can dual boot and test performance on your problems. This is important as my problems are mainly contact and perform differently to the vendors tests.

 

[GregLocock]

One catch with a multi cpu approach is that you might move from solving in RAM to virtual memory. If that happens then any advantage you might think you'll see from multithreading will be trashed.

As a vague example 5e5 dof runs in 1.5 gb of RAM.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Clearly, the performance will depend on the particular nature of the processing. A data-intensive algorithm that requires globs of data from secondary store will choke in a quad-core system, since the external buses are a limiting factor.

However, an algorithm that can happily thrash on the same few data bits for a long time should get a processing boost in a quad-core.

TTFN

FAQ731-376

 

[johnhors]

For largish jobs (circa 4 million DOF's) , I have found that Abaqus (the software used by the OP) benefits greatly from using multiple processors.