[gmx-developers] Re: OpenMP on Bluegene/Q runtime error

Jeff Hammond jhammond at alcf.anl.gov
Sat Mar 16 20:23:09 CET 2013

The XL OpenMP runtime on Blue Gene/Q didn't support nested parallelism.

However, in any case, you need to set the environment variable
OMP_NESTED=TRUE for this to work.  GCC does not enable nested
parallelism by default in the versions I tested (GCC 4.2.1 over LLVM
and GCC 4.7 on Mac, GCC 4.4.6 on BG/Q)

(Note that I tried to respond via
but it hasn't been accepted yet.  I apologize if this is a duplicate.
This answer is more complete anyways.)


Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381

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