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OpenMP Home PageBARRIER Directive
!$OMP BARRIER
The BARRIER directive synchronizes all threads in a team. When encountered, each thread waits until all of the others threads in that team have reached this point.
Example
!Filename: barrier.f90
!
!This shows use of the BARRIER directive.
!
PROGRAM ABARRIER
IMPLICIT NONE
INTEGER:: L
INTEGER:: nthreads, OMP_GET_NUM_THREADS
INTEGER:: tnumber, OMP_GET_THREAD_NUM
!$OMP PARALLEL SHARED(L) PRIVATE(nthreads,tnumber)
nthreads = OMP_GET_NUM_THREADS()
tnumber = OMP_GET_THREAD_NUM()
!$OMP MASTER
PRINT *, ' Enter a value for L'
READ(5,*) L
!$OMP END MASTER
!$OMP BARRIER
!$OMP CRITICAL
PRINT *, ' My thread number =',tnumber
PRINT *, ' Number of threads =',nthreads
PRINT *, ' Value of L =',L
PRINT *, ''
!$OMP END CRITICAL
!$OMP END PARALLEL
END PROGRAM ABARRIER
Compiling and running on franklin:
> cat barrier.pbs
#PBS -N barrier
#PBS -j oe
#PBS -o barrier.out
#PBS -q interactive
#PBS -S /bin/bash
#PBS -l mppwidth=1
#PBS -l mppnppn=1
#PBS -l mppdepth=2
#PBS -l walltime=00:05:00
#PBS -V
cd $PBS_O_WORKDIR
ftn -o barrier -mp=nonuma -Minfo=mp barrier.f90
export OMP_NUM_THREADS=2
aprun -n 1 -N 1 ./barrier < ninety
> cat ninety
90
> qsub barrier.pbs
500868.nid00003
> cat barrier.out
/opt/xt-pe/2.0.44a2/bin/snos64/ftn: INFO: linux target is being used
barrier.f90:
barrier:
12, Parallel region activated
16, Begin master section
21, End master section
23, Barrier
27, Begin critical section __cs_unspc
30, End critical section __cs_unspc
Parallel region terminated
Enter a value for L
My thread number = 0
Number of threads = 2
Value of L = 90
My thread number = 1
Number of threads = 2
Value of L = 90
Application 4736056 resources: utime 0, stime 0
