Re: [Starpu-devel] Tags and Sequential Consistency

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

Hello,

Cyril Bordage, le Fri 15 Mar 2013 01:14:43 +0100, a écrit :
> there is my situation :
>   - I submit a task B, depending by tag on the task A, which reads a data H
>   - I submit a task A (with a callback, so the order can be different) which
> writes H.

Oh!

That can explain things we were wondering today indeed :)

> Could not Starpu detect this pattern and do not add the automatic 
> dependency ?

I'd rather avoid this: that'd introduce obscure behaviors.

> Or maybe is it possible to warn in the debug mode ?

When StarPU does not progress any more, it could indeed have some code
to look for circular dependencies.

> This problem is that, in my case, I have other tasks for which I want to
> benefit from the automatic dependency. For example a task C, submitted after
> the task B and writting H. So, I have handled it in a different way, but it 
> is
> a suggestion.

It would be easy to add a "sequential_consistency" field to the task
structure, defaulting to 1, and sequential consistency would be enabled
only if both the data and the task have enabled it.

Samuel