[Starpu-devel] Unexpected behavior - Not making task ready when they could be

[Berenger Bramas <berenger.bramas@inria.fr>]

Hello,

I am using starpu in a project that requires the STARPU_COMMUTE.

And so I am working with the svn trunk (taken the 12/02/2015).

However it seems that starpu is not turning tasks to ready even if there is no reason not to do it.

I attach to this email a small example that illustrate this behavior, it is a simple C++ file that use STARPU_COMMUTE (testCommute.cpp)

(and also a home made version of the STARPU_COMMUTE with sequential consistency turned to false for some handles testFakeCommute.cpp).

In the test I am submitting lots of tasks that use two handles in STARPU_RW|STARPU_COMMUTE.

The degree of parallelism is huge (as it is shown in the dag, dag.dog & dag.pdf) but StarPU has to finish a task to insert a new one as the trace is showing (paje.trace).

I suppose that it is just a matter of: when starpu finish a task with a COMMUTE what dependencies it will release.

Please see:

https://zimbra.inria.fr/home/berenger.bramas@inria.fr/Briefcase/Public/StarPU

The algorithm of task insertion I am using in the test is:

================================================

for i from 0 to nbA

    insert task handles[i] mode STARPU_RW|STARPU_COMMUTE

    for j from 0 to nbA

        if i != j

              insert task handles[i] mode STARPU_RW|STARPU_COMMUTE, and handles[j] mode STARPU_RW|STARPU_COMMUTE

================================================

Do you think you may change this behavior and move a task that can be computed into the ready tasks?

I am also available to discuss that in person :)

Thanks.

Bérenger Bramas

HiePACS Project

Tel (05 24 57) 40 76
INRIA BORDEAUX Sud Ouest