Technical data

Writing Parallel Fortran

I is a loop index variable for the C$DOACROSS loop, so it is LASTLOCAL

by default. However, even though J is a loop index variable, it is not the loop

index of the loop being multiprocessed and has no special status. If it is not

declared, it is given the normal default of SHARE, which would be wrong.

C$&

Occasionally, the clauses in the C$DOACROSS directive are longer than one

line. The C$& directive is used to continue the directive onto multiple lines.

C$DOACROSS share(ALPHA, BETA, GAMMA, DELTA,

C$& EPSILON, OMEGA), LASTLOCAL(I,J, K, L, M, N),

C$& LOCAL(XXX1, XXX2, XXX3, XXX4, XXX5, XXX6, XXX7,

C$& XXX8, XXX9)

The C$ directive is considered a comment line except when multiprocessing.

A line beginning with C$ is treated as a conditionally compiled Fortran

statement. The rest of the line contains a standard Fortran statement. The

statement is compiled only if multiprocessing is turned on. In this case, the

C and $ are treated as if they are blanks. They can be used to insert

debugging statements, or an experienced user can use them to insert

arbitrary code into the multiprocessed version.

C$ PRINT 10

C$ 10 FORMAT('BEGIN MULTIPROCESSED LOOP')

C$DOACROSS LOCAL(Ii), SHARE(A,B)

DO I = 1, 100

CALL COMPUTE(A, B, I)

END DO