Reductions

• Original serial program is a reduction:

sum = 0.0

do 10 i=1,n

10 sum = sum + a(i)

• Correct but slow program: (Critical section is whole loop)

sum = 0.0

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

c$omp do

do 10 i=1,n

c$omp critical

sum = sum + a(i)

c$omp end critical

10 continue

c$omp end parallel

Previous slide

Next slide

Back to first slide

View graphic version