Macrotask Synchronization: LOCK

• ‘critical section’: use lock variable as semaphore

• additional calls outside the parallel region needed:

  • call PLASGN(ilock) : assign a lock to variable ilock
  • call PLFREE(ilock) : release the lock variable ilock

• check lock status: IPLSTAT(ilock), IPLSTATL(ilock)

subroutine SUMUP( nstart, nend, sum, a )

common / locks / ilock

real a(*)

sumlocal = 0.0

do I = nstart, nend

sumlocal = sumlocal + a(I)

enddo

call PLLOCK( ilock )

sum = sum + sumlocal

call PLUNLOCK( ilock )

return

end

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