Directives and Optimization

The following are comment form directives useful for optimizing source code. See the XL Fortran User's Guide for information on optimizing XL Fortran programs and the compiler options that affect performance.

Assertive Directives

Assertive directives gather information about source code that is otherwise unavailable to the compiler. Providing this information can increase performance.

ASSERT CNCALL
INDEPENDENT PERMUTATION

Directives for Loop Optimization

The following directives provide different methods of loop unrolling to optimize the effectiveness of the DO construct in source code:

BLOCK_LOOP LOOPID
STREAM_UNROLL UNROLL
UNROLL_AND_FUSE
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