Barriers

• Barrier needed:

c$omp parallel private(suml,i)

c$omp& shared(sum,a,n)

c$omp do

do 10 i=1,n

10 suml = suml + a(i)

c$omp critical

sum = sum + suml

c$omp end critical

c$omp barrier

c$omp do

do 20 i=1,n

20 b(i) = b(i) / sum

c$omp end parallel

• Use at end of computing data before data is used

• Builtin barrier in END DO and END PARALLEL

• Careful when you tune DO with NOWAIT

• Assure helps find problems

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