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

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

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?

Samuel