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

Eric Lu eirc.lew at gmail.com
Tue Oct 15 21:38:47 EDT 2013


Hi, Zhunping

Yes, I checked it, it outputs what I set in enrionment.

printf("max_threads = %d \n", omp_get_max_threads() );   ==>
max_threads = 32


On Tue, Oct 15, 2013 at 9:44 PM, Zhunping Zhang <jzz at mit.edu> wrote:

> 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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