[Pw_forum] difference between cpu time and wall time

[Paolo Giannozzi]

With threads, the CPU time is the sum of the CPU time spent by all threads,
or something like that

Paolo

On Wed, Sep 30, 2015 at 1:16 PM, mohammed shambakey <shambakey1 at gmail.com>
wrote:

> Ok, thanks.
>
> I have a test that uses 96 physical cores WITHOUT thread. The output
> recorded time is:
>
> PWSCF        :     0h57m CPU        1h44m WALL
>
> By running the same experiement with 96 physical cores and 2 threads per
> core (total 192 cores). The output recorded time is:
>
> PWSCF        :     1h41m CPU        1h39m WALL
>
> CPU time in case of 2 threads is larger than NO threads, but wall time in
> case of 2 threads is less than NO threads. So, I just wonder about the
> meaning of each criteria? and which one I should consider for performance
> comparison?
>
> Regards
>
> On Wed, Sep 30, 2015 at 12:42 PM, Paolo Giannozzi <p.giannozzi at gmail.com>
> wrote:
>
>> Yes: "wall time" = "what the clock on the wall shows"
>>
>> Paolo
>>
>> On Wed, Sep 30, 2015 at 12:29 PM, mohammed shambakey <
>> shambakey1 at gmail.com> wrote:
>>
>>> Hi
>>>
>>> In output files, there is cpu time and wall time. Does wall time include
>>> cpu time plus any time for transer, I/O, and any thing else?
>>>
>>> Regards
>>>
>>> --
>>> Mohammed
>>>
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>>> Pw_forum at pwscf.org
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>>>
>>
>>
>>
>> --
>> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> Phone +39-0432-558216, fax +39-0432-558222
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
>
> --
> Mohammed
>
> _______________________________________________
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> Pw_forum at pwscf.org
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>



-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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