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poor pgi openmp performance??
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steve.xu



Joined: 20 Feb 2012
Posts: 25

PostPosted: Thu Aug 02, 2012 2:56 am    Post subject: Reply with quote

Hi, Mat
Do you and your colleague have any update for my question??
Thanks
Steve
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mkcolg



Joined: 30 Jun 2004
Posts: 6208
Location: The Portland Group Inc.

PostPosted: Fri Aug 03, 2012 1:39 pm    Post subject: Reply with quote

No, sorry.
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mkcolg



Joined: 30 Jun 2004
Posts: 6208
Location: The Portland Group Inc.

PostPosted: Fri Aug 03, 2012 3:00 pm    Post subject: Reply with quote

I spoke too soon. Craig sent me the following:

Hi Mat,

I have an update for this customer request. The issue with the code
that the customer shows is how we handle nested task regions up to
and including the 12.6 release.In this case, some piece of code goes
parallel, then ends up generating ONE task within this parallel region and
this task is registered in an OMP single region. See code below. The only thing
this task does is call a subroutine called 'test'. So what happens is, a
single OMP thread registers the task. Then an OMP thread ends up
executing the task, which is just a call to subroutine test. Within this
subroutine, this OMP thread encounters more task regions. Since these
are nested, we choose to execute them immediately and thus end up
running them serially.

I tested this with the soon to be released 12.8 compiler, and we now support
nested task regions with a few exceptions. So my recommendation would be
for the customer to download 12.8 and try running their code again. If it still
does not show any significant speedup when run with more than one OMP
thread, we will need to get more details on the exact code pieces where they
are using task regions to see if they may be falling into one of the exceptional
cases.

-craig
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