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

[Maxim Abalenkov <maxim.abalenkov@gmail.com>]

Dear all,

How are you? I hope all is well with you. I need help please. I’m parallelising a stencil-based C code for shared-memory using StarPU. The general algorithm consists of five computation phases launched in a loop over time:

initialise StarPU

create data handles for arrays

register data with StarPU

create vector block filter

apply filter to partition data

for (int t = 0; t < tmax; t++) {

calc_phase1_starpu;

calc_phase2_starpu;

calc_phase3;

calc_phase4;

calc_phase5;

}

unpartition data

unregister data arrays

finalise StarPU

My questions are

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? 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?

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.

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. Thank you and have a great afternoon ahead!

—

Best wishes,

Maxim

Maxim Abalenkov \\ maxim.abalenkov@gmail.com
+44 7 486 486 505 \\ www.maxim.abalenkov.uk