Re: [Starpu-devel] About dag.dot

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

Xavier Lacoste, le Fri 14 Mar 2014 10:33:10 +0100, a écrit :
> I even submit tasks inside codelet's functions, at the end, without 
> callback function, is that bad ?

No, that is fine, but ATM StarPU will not put a dependency in the DAG in
such case. We could however try to do it, since StarPU knows which task
is currently executed.

> I submit a HETRF + TRSM only when all GEMM updates on it have been executed 
> and the unlocked list of GEMM when a HETRF + TRSM finishes.
> I did that to reduce the number of task that StarPU has to manage at a time 
> (but as far as I remember it was not really significant).
> Do you think it's better to submit all the graph from the main thread than 
> inside tasks ?

At the moment, the scheduler will not benefit from seeing more tasks
which are not ready yet, but this is the kind of thing it will do in the
future, so it becomes better to expose more of the graph.

StarPU does not have something like a "huge bag of all the tasks", so
it should not hurt to submit all tasks from the beginning. The problems
I can see with this is that the CPU time used for that will be spent on
one CPU, which will get degraded performance until the whole graph is
submitted. Also, you will have a corresponding memory consumption, to
record the whole graph.

Samuel