OpenMP question - ignoring OMP_NUM_THREADS?

OpenMP question - ignoring OMP_NUM_THREADS?

I use Intel Parallel Studio XE 2011 and Portland Group Fortran 12.1  on Windows.

I use Intel Composer_xe_2011 and Portland Group Fortran 10.x on Linux.

I have a numerical hydrodynamic model that I an running with openMP on several computers.

 

WINDOWS Observations  [Xeon W3570 4 core cpu]  ..

1) Intel fortran compiles and links in openMP. Code runs with openMP and yields a speedup of 1.43 with OMP_NUM_THREADS=8

2) Portland group compiles and links in openMP. Code runs with openMP and yields a speedup of 1.4 with OMP_NUM_THREADS=8

Summary: INTEL & PG BOTH WORK FINE ON WINDOWS

 

LINUX  Observations  - 2  machines 

1) Machine is a 4 processor AMD opteron 8360 SE with 4 cores per processor - 16 cores

     A ) Intel fortran compiles and links in openMP.  Code does not run with more than one thread  with multiple OMP_NUM_THREADS values

     B)  Portland group compiles and links in openMP. I can run the code with openMP and get a speedup of 1.38 with OMP_NUM_THREADS=12

2) Machine has 4  Intel Xeon 6-core Xeon E5649 cpus. - 24 cores - whoopie!

     A ) Intel fortran compiles and links in openMP.  Code does not run with more than one thread

     B)  Portland group compiles and links in openMP. I can run the code with openMP and get a speedup of 1.44 with OMP_NUM_THREADS=12

Summary:  BOTH MACHINES EXHIBIT A PROBLEM WITH INTEL FORTRAN

 

Problem with Intel Fortran on Linux:

I tried compiling and linking the code with Intel Fortran with both the dynamic openMP lib and the static openMP lib - both give just one thread running.

I have varied OMP_NUM_THREADS from 1 through 18 on the Linux Xeon system - only get one thread running.

Same behavior on the AMD system - varied OMP_NUM_THREADS from 1 through 16

 

Any suggestions? 

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