[Starpu-devel] How to wait for a subset of the tasks to complete

[Benoît Lizé <benoit.lize@gmail.com>]

Hello,

I'm trying to find the most "idiomatic" way to "wait" for the completion of a subset of the tasks I'm submitting before executing a cleanup task.

I have the following situation, within a larger program:

• Execute a bunch of tasks t1, ..., tn on a set of data handles d1, ..., dm
• When this set of tasks is done, execute one task (cleanup) which does not have any dependencies. It unregisters (among other things) d1, ..., dm

Only the implicit data depedencies are used in this program. I don't want to use partitionned data handles, and I don't want to have the cleanup task depending on the union of all the data handles of the tasks t1, ..., tn.

One way I could express what I want to do is to add a dummy read dependency for each task in t1, ..., tn and then a write dependency for the cleanup task. This looks a bit ugly. It seems that this would be a good use case for the explicit dependencies, especially with

 void starpu_task_declare_deps_array()

Is it possible to mix implicit and explicit dependencies in the same program ? Is there a better way, one that would not prevent me from using starpu_insert_task() for t1, ..., tn ? Are there performance penalties associated with each approach ?

Thank you,

-- 

Benoit Lize