Re: [Starpu-devel] Combined workers and OpenMP code

[Keisuke Fukuda <fukuda@matsulab.is.titech.ac.jp>]

Nicolas,

Thank you, it worked !



On Thu, Apr 26, 2012 at 8:53 PM, Nicolas Collin <nicolas.collin@inria.fr> 
wrote:
> On 04/25/2012 05:42 PM, Samuel Thibault wrote:
>>
>> Keisuke Fukuda, le Wed 25 Apr 2012 11:36:44 +0200, a écrit :
>>>
>>> starpu_combined_worker_get_size() always returns 1
>>
>> I notice that your program uses a regression-based performance model,
>> but it only submits tasks of the same size.  The scheduler does not
>> realize that it's still a task of the same size, which will not help the
>> performance model, and thus continues to try with 1, in the hope the
>> performance model will eventually provide estimations.
>>
>>> and only 1 thread runs in #pragma omp parallel for loop.
>>> OTOH, vector_scal example run 2-4 threads (although I expect 6 workers
>>> since
>>> the CPU is 6-core sandy bridge).
>>
>> Doesn't starpu_perfmodel_display show that it at least tried 6 a few
>> times, perhaps only to realize that it's less efficient than 2-4?
>>
>>> (2) Is there any way to let (or even force) StarPU to use a certain
>>> number of workers, i.e.
>>> just as the same number as of physical cores.
>>
>> You can use the execute_on_a_specific_worker field to force using a
>> combined worker.  Nicolas, is there any way to print the combined
>> workers tree?  Also, it seems that STARPU_MIN/MAX_WORKERSIZE are not
>> documented at all, could you handle that?
>
> There is no function to print the combined worker tree yet.
> You can force StarPU to create the desired combined worker by declaring
> STARPU_SINGLE_COMBINED_WORKER to 0 and declaring STARPU_MIN/MAX_WORKER_SIZE
> to the desired number.
> For example :
> STARPU_CALIBRATE=2 STARPU_NCUDA=0 STARPU_NOPENCL=0 STARPU_MIN_WORKERSIZE=6
> STARPU_MAX_WORKERSIZE=6 STARPU_SINGLE_COMBINED_WORKER=0 ./simple_omp
>
> Indeed I'm going to write a paragraph about STARPU_MIN/MAX_WORKERSIZE.
>
> Regards
>  -- Nicolas



-- 
------------------------------------------
FUKUDA, Keisuke<fukuda@matsulab.is.titech.ac.jp>
Dept. of Math. & Comp. Sciences
Satoshi Matsuoka Lab.,
Tokyo Institute of Technology

福田圭祐 <fukuda@matsulab.is.titech.ac.jp>
東京工業大学　数理・計算科学専攻　松岡研究室