OpenMP thread stops

General OpenMP discussion

Re: OpenMP thread stops

Postby guyColumbus » Sun Oct 14, 2012 3:20 pm

My code is in the following format :

CALL OMP_SET_NUM_THREADS(2)
! $OMP PARALLEL shared (...) private(..)

!OMP DO

Do s=1,10
.
.
.
PARDISO (..)
.
.
.
END DO
!OMP END DO
!$OMP END PARALLEL

For every loop, I need to solve a different linear equation. So pardiso has to be called during every loop.

Unfortunately, the suggested measures did not help.

- Setting OMP_WAIT_POLICY to passive did not help

- Arguments I have passed are all behaving fine, othewise I should have got the wrong answers when both the threads are active. Its only when one thead stops that the problem occurs.

- Nested parallelism is enabled.

- I will give another example. When I set OMP_SET_NUM_THREADS = 2, and include PARDISO inside a critical construct like this :
!$OMP CRITICAL
PARDISO(...)
!$OMP END CRITICAL

and run the code, even then PARDISO refuses to run and just hangs. For whatever reason pardiso expects both the threads to be active, otherwise it won't run. If one of the threads is inactive (when OMP_SET_NUM_THREADS = 2) then it hangs. However if I make OMP_SET_NUM_THREADS = 1, then the code runs fine.

Very confused.
guyColumbus
 
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Joined: Wed Oct 10, 2012 3:04 pm

Re: OpenMP thread stops

Postby guyColumbus » Sun Oct 14, 2012 3:58 pm

I changed 'msglvl' to 1 to see where pardiso is hanging, i got the message

=== PARDISO is running in In-Core mode, because iparam(60)=0 ===
Percentage of computed non-zeros for LL^T factorization
0 % 1 % 2 % 3 % 4 % 5 % 6 % 7 % 8 % 9 % 10 % 11 % 12 % 13 % 14 % 15 % 16 % 17 % 18 % 19 % 20 % 21 % 22 % 23 % 24 % 25 % 26 % 27 % 28 % 29 % 30 % 31 % 32 % 33 % 66 % 99 % 100 %

and there it hangs. The next stage is 'solve'. So it is not able to solve when one of the threads is inacitve
guyColumbus
 
Posts: 5
Joined: Wed Oct 10, 2012 3:04 pm

Re: OpenMP thread stops

Postby MarkB » Tue Oct 16, 2012 2:21 am

I think this is most likely a PARDISO problem. You could try contacting the authors: http://www.pardiso-project.org/contact
MarkB
 
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Joined: Thu Jan 08, 2009 10:12 am
Location: EPCC, University of Edinburgh

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