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41 lines
1.0 KiB
Fortran
41 lines
1.0 KiB
Fortran
! @@name: acquire_release.4.f90
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! @@type: F-free
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! @@compilable: yes, omp_5.0
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! @@linkable: yes
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! @@expect: success
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program rel_acq_ex4
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use omp_lib
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integer :: x, y, thrd
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integer :: tmp
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x = 0
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!! !!! THIS CODE WILL FAIL TO PRODUCE CONSISTENT RESULTS !!!!!!!
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!! !!! DO NOT PROGRAM SYNCHRONIZATION THIS WAY !!!!!!!
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!$omp parallel num_threads private(thrd) private(tmp)
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thrd = omp_get_thread_num()
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if (thrd == 0) then
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!$omp critical
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x = 10
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!$omp end critical
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! an explicit flush directive that provides
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! release semantics is needed here to
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! complete the synchronization.
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!$omp atomic write
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y = 1
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!$omp end atomic
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else
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tmp = 0
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do while(tmp == 0)
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!$omp atomic read acquire ! or seq_cst
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tmp = x
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!$omp end atomic
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end do
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!$omp critical
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print *, "x = ", x !! !! NOT ALWAYS 10
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!$omp end critical
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end if
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!$omp end parallel
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end program
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