Technical data

76
Chapter 5: Fortran Enhancements for Multiprocessors
See Example 5 in “Analyzing Data Dependencies for Multiprocessing” on
page 79 for more information on this example.
Example 3
DO 10 I = M, K, N
X = D(I)**2
Y = X + X
DO 20 J = I, MAX
A(I,J) = A(I,J) + B(I,J) * C(I,J) * X + Y
20 CONTINUE
10 CONTINUE
PRINT*, I, X
Here, the final values of I and X are needed after the loop completes. A
correct directive is
C$DOACROSS LOCAL(Y,J), LASTLOCAL(I,X), SHARE(M,K,N,ITOP,A,B,C,D)
DO 10 I = M, K, N
X = D(I)**2
Y = X + X
DO 20 J = I, ITOP
A(I,J) = A(I,J) + B(I,J) * C(I,J) *X + Y
20 CONTINUE
10 CONTINUE
PRINT*, I, X
or you could use the defaults
C$DOACROSS LOCAL(Y,J), LASTLOCAL(X)
DO 10 I = M, K, N
X = D(I)**2
Y = X + X
DO 20 J = I, MAX
A(I,J) = A(I,J) + B(I,J) * C(I,J) *X + Y
20 CONTINUE
10 CONTINUE
PRINT*, I, X