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OpenMP+gfortran performance extremely variable between dlopen's of libgomp
- From: "Anand Patil" <anand dot prabhakar dot patil at gmail dot com>
- To: gcc-help at gcc dot gnu dot org
- Date: Sun, 13 Jan 2008 19:19:43 -0800
- Subject: OpenMP+gfortran performance extremely variable between dlopen's of libgomp
Hi all,
As in my last help request, I'm using gfortran 4.2.1 from Ubuntu
Gutsy's apt-get, with the patch from bug 28482 (
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28482 ) applied so that I
can dlopen libgomp. I find that the performance of my subroutines
varies greatly if I reload libgomp, but if I rerun the subroutines
several times for the same load of libgomp performance is fairly
constant. Other information that may be relevant:
- The number of threads stays the same (I have OMP_DYNAMIC=False).
- The relative speedup from OpenMP (wall time / CPU time) stays
relatively constant.
I don't even know where to start looking for the source of this
behavior. Any tips?
Thanks,
Anand Patil