module library

  use omp_lib!, only: &
       !omp_get_thread_num, &
       !omp_get_num_thread

  use, intrinsic:: iso_c_binding, only: &
       c_int

  use types, only: &
       int32, real64

  implicit none


  interface
     subroutine usleep(us) bind (C)
      import c_int
      integer(c_int), value :: us
    end subroutine usleep
  end interface


contains

  subroutine hello()

    implicit none

    integer(kind=int32) :: &
         nthreads, tid
    real(kind=real64) :: &
         r, t

    ! Fork a team of threads giving them their own copies of variables
    !$OMP PARALLEL PRIVATE(NTHREADS, TID, R, T)


    ! Obtain thread number
    tid = omp_get_thread_num()
    call random_number(r)
    call usleep(int(r * 1.d6))
    t = r
    print *, 'Hello World from thread  = ', 10+tid, ', t = ', t
    call random_number(r)
    call usleep(int(r * 1.d6))
    t = t + r
    print *, 'Hello Planet from thread = ', 10+tid, ', t = ', t
    call random_number(r)
    call usleep(int(r * 1.d6))
    t = t + r
    print *, 'I am done from thread    = ', 10+tid, ', t = ', t

    ! Only master thread does this
    if (tid == 0) THEN
       nthreads = omp_get_num_threads()
       PRINT *, 'Number of threads = ', nthreads
    END IF

    ! All threads join master thread and disband
    !$OMP END PARALLEL

    PRINT *, 'All done.'

  end subroutine hello

end module library