Basic HTML version of Foils prepared August 29 98

Foil 44 Reductions

From Designing and Building Parallel Programs 2: openMP Shared Memory Programming Language DoD Modernization Tutorial -- 1995-1998. by Ian Foster, Gina Goff, Ehtesham Hayder, Chuck Koelbel(Some foils prepared by Kuck & Associates, Inc.)
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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