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

[Philippe SWARTVAGHER <philippe.swartvagher@inria.fr>]

Le 11/10/2024 à 14:43, Samuel Thibault a écrit :
> 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.

If your non-StarPU code accesses data managed by StarPU, you should also 
call

starpu_data_acquire(data_handle, STARPU_R /* or STARPU_RW */)

before your non-StarPU code reads (or writes) the StarPU data. This 
makes sure the tasks which manipulate data_handle are finished. Then, to 
tell StarPU you are finished working with this memory and it can start 
other tasks using this handle, you have to call

starpu_data_release(data_handle)

Have a look for instance on this example: 
https://gitlab.inria.fr/starpu/starpu/-/blob/f3e318b326666c5b279680d5a57fc0468e8c1876/examples/filters/fvector_pick_variable.c

Or, instead, you can just call

starpu_task_wait_for_all()

but depending on what your application does, you may not need to wait 
for all tasks to finish to start reading/writing one piece of data.

Not sure if this will solve your problems, but it was missing from your 
description of how your program uses StarPU.

--
Philippe SWARTVAGHER
Assistant Professor @ ENSEIRB-MATMECA
Research team Topal @ Inria Bordeaux-Sud Ouest