Re: [Starpu-devel] CUDA task and GCC plugin

[Mehdi AMINI <mehdi.amini@silkan.com>]

Hi,

> > Currently I always end up with a linker error.
>
> Oups, that’s a genuine bug (I’ve reproduced it.)  I’ll let you know when
> a fix is available.

Thanks ! :-)


> > I also have an issue related to implicit cpu implementations and -O3
> > gcc flag which seems to be broken. I'm testing a simple task call with
> > a CPU and a CUDA implementation. Using -O3 the CPU task is always
> > executed while without the -O3 flag the CUDA task is correctly
> > executed. Is it a known issue ?
>
> I believe there’s nothing wrong here: the default scheduler (‘eager’)
> makes non-deterministic scheduling decisions, and just happened to favor
> CPU over CUDA for some reason.

It seems to be reproducible, I mean 100%
Moreover StarPU was compiled with --disable-cpu ; and finally I even 
reproduce it using STARPU_NCPUS=0 !

My guess is that -O3 may trigger an inlining of the original implicit 
implementation at call site so that the StarPU wrapper is never called 
and instead there directly the code of the CPU function.

> Now, the CPU back-end can be disabled at run-time, forcing the scheduler
> to use GPUs only:
>
>    $ STARPU_NCPUS=0 ./compile-test.sh

You missed the -O3 flag here, try again with :

STARPU_NCPUS=0 OPT_FLAG=-O3 ./compile-test.sh


Mehdi