[parsec-users] the OpenMP version blackscholes has No speedup when has more than 4 cores

Zhunping Zhang jzz at mit.edu
Tue Oct 15 09:44:54 EDT 2013


Just to make sure, does the output of omp_get_max_threads() look sensible?

Cheers,
---Justin


Quoting Eric Lu <eirc.lew at gmail.com>:

> Hi,
>  The time I measure just the parallel scope: bs_thread(), not include the
> file read part, so the effect of reading files by main thread is removed.
>
>  And I compare OpenMP version with pthread or TBB, it seems TBB and
> pthreads has much better performance results. So, I guess it is the gcc'
> implementation for OpenMP maybe not fit to this program.
>
> Thanks!
>
> Eric
>
>
> On Tue, Oct 15, 2013 at 9:58 AM, kishore kumar 
> <kishoreguptaos at gmail.com>wrote:
>
>> What do you mean by poor performance? Is it speedup? I guess that you run
>> blackscholes with native inputs. With large inputs, blackscholes main
>> thread does more work (serial execution -- reading input file, etc.,)
>> compared to the worker threads (parallel execution). Around 95% of the
>> entire execution time, you only see one thread, i.e., main thread. May be
>> you want to read "Thread Reinforcer: Dynamically Determining Number of
>> Threads" paper.
>>
>> Thanks.
>>
>> Best,
>> Kishore Kumar Pusukuri
>> http://www.cs.ucr.edu/~kishore
>>
>>
>> On Mon, Oct 14, 2013 at 6:34 PM, Eric Lu <eirc.lew at gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I run PARSEC2.1 on Intel E7520 machine, the os is centos6.3, the gcc-4.7
>>> compiler. The machine has 32 cores in total, and the results seems
>>> blackscholes has too poor performance.
>>> The data shows as follow:
>>> OpenMP
>>> proc blackscholes
>>> 1 0.998269
>>> 2 1.80499
>>> 4 1.763301
>>> 8 1.550916
>>> 16 1.542871
>>> 32 2.508076
>>>
>>>
>>>
>>> Best Regards!
>>>
>>>
>>> Eric
>>>
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>>>
>>
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>



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