Nested parallel section exception

[Hartmut Kaiser]

When using the HPX backend we see exceptions reporting that a 'nested parallel section' was detected. Some analysis showed that this exception is not caused by actually 'nesting' operations but by running several Blaze operations concurrently on different threads, causing several parallel sections to be active at the same time.

Is there a way to avoid these exceptions? Having several parallel sections concurrently active (nested or otherwise) is not a problem for HPX. Even worse, enforcing such a limitation severely limits the usability of Blaze for HPX applications.

[Hartmut Kaiser]

We probably could remove the BLAZE_PARALLEL_SECTION from the HPX backend just fine. Would you accept a PR doing that?

[Klaus Iglberger]

Hi Hartmut!

Thanks for creating this issue. The behavior is expected and documented in the wiki (see also this related issue). However, it stems from the limitations of the OpenMP backend. If you have tested that the parallel execution of several parallel operations works with the HPX backend, than this check can be removed. Thus I would accept an according pull request.

Best regards,

Klaus!

[Hartmut Kaiser]

Thanks Klaus. I have created a PR (https://bitbucket.org/blaze-lib/blaze/pull-requests/18/removing-blaze_parallel_section-in-the-hpx) to remove the parallel sections for the HPX backend.

[Klaus Iglberger]

The issue has been resolved by pull request #18. The fix is immediately available via cloning the Blaze repository and will be officially released in Blaze 3.3.

[Hartmut Kaiser]

Thanks a lot!