Re: [starpu-devel] [StarPU for stencil-based code: logic, starpu_shutdown error]

[Samuel Thibault <samuel.thibault@inria.fr>]

Hello,

Maxim Abalenkov, le ven. 11 oct. 2024 12:16:54 +0100, a ecrit:
> Can you please dedicate five minutes to read and respond to my email?

Now that the IPDPS deadline is over, yes.

>     1) First two phases I already converted to StarPU. Can you please check 
> I’m
>     using StarPU in a performant manner, i.e. can you confirm that it is 
> better
>     to register and partition the data before the main time loop iterations 
> and
>     un-partition it at the end?

Yes.

>     So far I see very strong performance degradation of my code. It
>     is worse than the sequential version of the code. Maybe it is not
>     recommended to mix StarPU code with non-StarPU sequential code?

No, that should not really be a problem. But how large your tasks
are? See the checklist item about task sizes:

https://files.inria.fr/starpu/doc/html/CheckListWhenPerformanceAreNotThere.html#CheckTaskSize

That being said, you will probably want to put starpu_pause() /
starpu_resume() around your not-yet-starpufied code, otherwise StarPU
monopolizes all CPU cores, which can thus degrade the performance of the
non-starpufied code.

>     2) My code crashes with the following error message at the very end of
>     execution:
> 
> 
>         [starpu][_starpu_task_submit][assert failure] starpu_init must be
>         called (and return no error) before submitting tasks.
> 
>         Assertion failed: (0 && "starpu_is_initialized()"), function
>         _starpu_task_submit, file task.c, line 956.

Please also post a backtrace, to make sure of the context of the call.

>     Would you please guide me on how to debug this error? I’m sure I called
>     ‘starpu_init’ before I submitted my tasks. I suspect this error is 
> issued
>     by the ‘starpu_shutdown’ routine at the very end of my program.

The error looks like you have called starpu_shutdown within your
program, before the last task submission.

Posting your actual code would help to check what is going wrong.

Samuel