if I use thread binding in the following way:
export OMP_NUM_THREADS=8
export GOMP_CPU_AFFINITY="0 1 2 3 4 5 6 7"
for code that has three parallel regions:
!$omp parallel default(private) shared(bindings,n_thread)
!$omp end parallel
!$omp parallel default(private) shared(bindings,n_thread) num_threads(2)
!$omp end parallel
!$omp parallel default(private) shared(bindings,n_thread)
!$omp end parallel
I get the following:
> ./a.out
Entering first parallel region all threads
bindings are 0 1 2 3 4 5 6 7
Entering second parallel region using two threads
bindings are 0 1
Entering third parallel region using all threads
bindings are 0 1 0 1 2 3 4 5
so it the last parallel section 2 times 2 threads bind to the same CPU (this is
also what is effectively happing looking at the CPU usage in top).
this seems to be happening for gcc 4.3 - 4.6
The testcase will be attached.
--
Summary: unexpected thread binding for openmp
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jv244 at cam dot ac dot uk
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44833
