[Nek5000-users] question about efficient running nek5000

[nek5000-users at lists.mcs.anl.gov]

Hi Aleks,

Approximately I can do that!

Ami

On Wed, Feb 4, 2015 at 2:30 PM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi Ami,
>
> Could you try your 12 core-per-node case running with only 11 cores per
> node (and increasing the total number of nodes to keep the number of CPU
> fixed)?
>
> Aleks
>
>
> On Wed, 4 Feb 2015, nek5000-users at lists.mcs.anl.gov wrote:
>
>  Mike,
>>
>> Thanks for your answer!, Total grid points is 32499936, which I believe it
>> is greater than 20k for both cases!
>>
>> Ami
>>
>> On Wed, Feb 4, 2015 at 2:17 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>  Hi Ami,
>>>
>>> How many nodes were in your simulation? Nek scales well if your number of
>>> gridpoints per core is large enough, e.g., greater than 20K or so in my
>>> experience.
>>>
>>> It's not clear to me if the power-of-two issue would be the cause here;
>>> perhaps Paul could comment.
>>>
>>> Mike
>>>
>>> On Feb 4, 2015, at 12:09 PM, <nek5000-users at lists.mcs.anl.gov>
>>>  wrote:
>>>
>>>  Hi,
>>>>
>>>> I ran nek5000 on 1024 CPUs which is divided to 128 nodes and 8 cores per
>>>>
>>> node, and the same problem on 1200 CPUs with 100 nodes and 12 cores per
>>> node, however in second case I got lower efficiency, simulation goes
>>> slower
>>> about 5~8 percent!! I ran both cases on the same cluster!! Does anyone
>>> have
>>> any idea why I do not get higher efficiency with the higher number of
>>> CPUs
>>> but less nodes involved!? Could memory be a limitation here or since
>>> numbers in first case are power of 2, it is more efficient!?
>>>
>>>>
>>>> Thanks,
>>>> Ami
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