[Openmp-dev] [cfe-dev] Implicit/Explicit task yielding in Clang v5.0.0 OpenMP Implementation

Jeff Hammond via Openmp-dev openmp-dev at lists.llvm.org
Thu Mar 14 11:57:07 PDT 2019

(adding omp-dev; cfe-dev isn't the right place for this, so please don't
copy on subsequent replies)

OpenMP taskyield is useless, by design.  It can be a no-op and there is no
way to guarantee that OpenMP tasks make concurrent progress.
https://github.com/mpi-forum/mpi-issues/issues/75 has some context.  The
OpenMP committee has been discussing this a bunch recently but one proposed
solution was to deprecate taskyield rather than fix it.

I encourage you to discuss your requirements with vendors who supply you
with hardware and/or compilers, since those companies have representatives
in the OpenMP language committee.


On Thu, Sep 20, 2018 at 9:39 AM Dawson, Mark via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> While an implementation of OpenMP is **allowed** to insert implicit
> switching points in a task region (i.e., #pragma omp task), I as the
> developer can make use of the standard’s explicit task yielding if need be
> (i.e., #pragma omp taskyield). My question is whether the Clang v5.0.0
> implementation employs such implicit task yielding, or is it necessary for
> me to do so explicitly?
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Jeff Hammond
jeff.science at gmail.com
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