Re: [Starpu-devel] Performance profiling of tile low rank cholesky (HiCMA) with StarPU on distributed memory systems

[Kadir Akbudak <kadir.akbudak@kaust.edu.sa>]

Dear All,

I have attached an experimental case:

* Parallel cholesky algorithm
* 1080K-by-1080K matrix, best block size out of 4 block sizes is reported
* different number of nodes (16, 32, 64,128,256, 512 and 1024; one MPI
rank per node)
* different number of threads per NODE (1,2,4,8,16,31; number of
physical cores is 32)
* different schedulers: lws, prio and ws

My question is:

The brown line (time for 512 nodes) should not go up while the number
of threads per node increases. How can I achieve this?

Thanks,
Kadir


On Wed, May 2, 2018 at 9:44 PM, Hatem Ltaief <hatem.ltaief@kaust.edu.sa> 
wrote:
> Kadir should update soon on switching to ws or lws, in situations where 
> cores don’t have enough work (i.e., in strong scaling mode of operations).
> Thx,
> H
>> On May 2, 2018, at 8:30 PM, Samuel Thibault <samuel.thibault@inria.fr> 
>> wrote:
>>
>> Aniello Esposito, le mer. 02 mai 2018 17:08:48 +0000, a ecrit:
>>> As Hatem already emphasized, the main point here is the behavior of 
>>> threads
>>> in the presence of not enough work. We would have expected no real 
>>> difference if even
>>> too many threads are used.
>>
>> Sure, but that's precisely where a centralized scheduler like prio would
>> suffer from all the idle threads trying to pick up work from the central
>> place, tasks getting executed randomly on various CPUs, etc.
>>
>> Samuel
>

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Attachment: lws.pdf
Description: Adobe PDF document

Attachment: prio.pdf
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Attachment: ws.pdf
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