[CIG-MC] Citcom runtime on Lonestar vs Ranger (Teragrid): Insights/experience?

[Magali Billen]

Hi Eh,
thanks for doing this and posting the results. Its very helpful.
Magali

On Feb 22, 2010, at 10:22 AM, Eh Tan wrote:

> Walter Landry wrote:
>> Finally, memory pressure may have an effect.  The AMD's generally  
>> have
>> better memory performance, but there is more contention since there
>> are 16 cores accessing the same memory, rather than 4 cores accessing
>> 4 separate banks of memory.
>>
>
> The memory pressure (bandwidth limit) is indeed a major bottleneck for
> CitcomCU and CitcomS. Generally, FEM codes require high memory  
> bandwidth
> to solve the sparse matrix inversion. Longstar machine has two dual- 
> core
> CPUs, and Ranger machine has four quad-core CPUs. All cores in the CPU
> share the same memory bandwidth. As a result, Ranger has effectively
> half memory bandwidth per core, compared to Longstar. This can affect
> the speed by 5-10%.
>
> I've done a speed benchmark showing the effect of memory bandwidth on
> our cluster, which has two quad-core CPUs.
> http://www.geodynamics.org/cig/Members/tan2/scaling/document_view
>
>
> Cheers,
> Eh Tan
>
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> CIG-MC at geodynamics.org
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