Reductions

• Serial program is a reduction:

sum = 0.0

do 10 i=1,n

10 sum = sum + a(i)

Correct (but slow) program:

sum = 0.0

c$omp parallel private(i) shared(sum,a,n)

c$omp pdo

do 10 i=1,n

c$omp critical

sum = sum + a(i)

c$omp end critical

10 continue

c$omp end parallel

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