9.2. Worksharing Constructs Inside a critical Construct

The following example demonstrates using a worksharing construct inside a critical construct. This example is conforming because the worksharing single region is not closely nested inside the critical region. A single thread executes the one and only section in the sections region, and executes the critical region. The same thread encounters the nested parallel region, creates a new team of threads, and becomes the primary thread of the new team. One of the threads in the new team enters the single region and increments i by 1. At the end of this example i is equal to 2.

//%compiler: clang
//%cflags: -fopenmp

/*
* name: worksharing_critical.1
* type: C
*/
void critical_work()
{
  int i = 1;
  #pragma omp parallel sections
  {
    #pragma omp section
    {
      #pragma omp critical (name)
      {
        #pragma omp parallel
        {
          #pragma omp single
          {
            i++;
          }
        }
      }
    }
  }
}

!!%compiler: gfortran
!!%cflags: -fopenmp

! name: worksharing_critical.1
! type: F-fixed
      SUBROUTINE CRITICAL_WORK()

        INTEGER I
        I = 1

!$OMP   PARALLEL SECTIONS
!$OMP     SECTION
!$OMP       CRITICAL (NAME)
!$OMP         PARALLEL
!$OMP           SINGLE
                  I = I + 1
!$OMP           END SINGLE
!$OMP         END PARALLEL
!$OMP       END CRITICAL (NAME)
!$OMP   END PARALLEL SECTIONS
      END SUBROUTINE CRITICAL_WORK