[Bug libgomp/37586] New: OpenMP thinks that I have 1 processor on an 8 processor pc

["rrpeter at sandia dot gov" <gcc-bugzilla at gcc dot gnu dot org>]

Hi,
I have tried various OpenMP examples on the web and got them all to work fine.
When I tried to parallelize some software that is part of a larger project, I
have had a problem; OpenMP reports only one processor available and so I get
only 1 thread. More details follow.

I am running on an dual quad-core PC. I use RHEL 5.2 and have used the gcc
4.3.2 compiler (compiled it myself) and the RedHat's "stock" 4.1.2 compiler
that has had OpenMP backported to it. Both exhibit the same problem.


In some simple example code (e.g., dotproduct_reduction.cpp that found on the
web), I can put in the following print:
#ifdef _OPENMP
cout << " Number of processors available:" << omp_get_num_procs() << " MAX
Number of threads " << omp_get_max_threads() << endl;
cout.flush();
#endif

and get something like:
Number of processors available:8 MAX Number of threads 8

The example runs 8 threads and appears to run on multiple processors. 

In my large project on the same computer:
#ifdef _OPENMP
cout << " Number of processors available:" << omp_get_num_procs() << " MAX
number of OpenMP threads " << omp_get_max_threads() << endl;
#endif

and get:
Number of processors available:1 MAX number of OpenMP threads 1

And so it doesn't parallelize. I am stumped! What could be causing OpenMP to be
confused with regard to the number of processors? I thought it might be
something in the compile, so I re-compiled absolutely everything with
"-fopenmp" turned on and it made no difference.

I tried setting the environment variable OMP_NUM_THREADS to 2 and got 2
threads, but only one processor was running the job.

Compile samples:
cd /home/hopper/UMBRA_4/umbra/SNL/rwm/buildRWM/utility && /usr/bin/g++-4.3.2
-DBOOST_ALL_NO_LIB -Dutility_EXPORTS -O3 -DNDEBUG -fopenmp -fPIC
-I/usr/include/boost-1_35 -I/home/hopper/UMBRA_4/umbra/SNL/rwm/TNT
-I/home/hopper/UMBRA_4 -Wall -fPIC -o CMakeFiles/utility.dir/matrix_math.o -c
/home/hopper/UMBRA_4/umbra/SNL/rwm/utility/matrix_math.cpp

cd /home/hopper/UMBRA_4/umbra/SNL/rwm/buildRWM/micp && /usr/bin/g++-4.3.2
-DBOOST_ALL_NO_LIB -Dmicp_EXPORTS -O3 -DNDEBUG -fopenmp -fPIC
-I/usr/include/boost-1_35 -I/home/hopper/UMBRA_4/umbra/SNL/rwm/utility
-I/home/hopper/UMBRA_4/umbra/SNL/rwm/CDF -I/home/hopper/UMBRA_4
-I/home/hopper/UMBRA_4/include/cstk2 -Wall -fPIC -o CMakeFiles/micp.dir/icp.o
-c /home/hopper/UMBRA_4/umbra/SNL/rwm/micp/icp.cpp

Link sample (everything is linked as a shared library)
Linking CXX shared library ../libutility.so
cd /home/hopper/UMBRA_4/umbra/SNL/rwm/buildRWM/utility && /usr/bin/cmake -E
cmake_link_script CMakeFiles/utility.dir/link.txt --verbose=1
/usr/bin/g++-4.3.2 -fPIC -O3 -DNDEBUG -fopenmp -Wl,--no-undefined -shared
-Wl,-soname,libutility.so -o ../libutility.so CMakeFiles/utility.dir/CharObj.o
CMakeFiles/utility.dir/Classify.o CMakeFiles/utility.dir/crc16_func.o
CMakeFiles/utility.dir/crc32_func.o CMakeFiles/utility.dir/dsvdfit.o
CMakeFiles/utility.dir/geometry.o CMakeFiles/utility.dir/math_funcs.o
CMakeFiles/utility.dir/math_predicate.o CMakeFiles/utility.dir/matrix_math.o
CMakeFiles/utility.dir/PCI.o CMakeFiles/utility.dir/rwm_status.o
CMakeFiles/utility.dir/statistics.o CMakeFiles/utility.dir/string_funcs.o
CMakeFiles/utility.dir/timing.o CMakeFiles/utility.dir/utility.o
CMakeFiles/utility.dir/ValIndex.o /usr/local/lib/libumb.so
-Wl,-rpath,/usr/local/lib

BTW, the .tgz file containing the source code (exclude *.o and*.so) for this
project has a size of 315788806, so its huge!


-- 
           Summary: OpenMP thinks that I have 1 processor on an 8 processor
                    pc
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rrpeter at sandia dot gov


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37586