Intel® Fortran Compiler 17.0 Developer Guide and Reference
When certain loop directives precede an array assignment statement, they affect the implicit loops that are generated by the compiler.
The following loop directives can affect array assignment statements:
The PREFETCH and NOPREFETCH directives also affect array assignment statements, but they are only available on Intel® MIC Architecture.
Usually only one of the general directives can precede the array assignment statement (one-dimensional-array = expression) to affect it. The BLOCK_LOOP and NOBLOCK_LOOP directives may precede array assignment statements with any rank variable on the left-hand-side of the assignment.
Other rules may apply to the general directives. For more information, see the description of each directive.
Consider the following:
REAL A(10), B(10) ... !DIR$ IVDEP A = B + 3
This has the same effect as writing the following explicit loop:
!DIR$ IVDEP DO I = 1, 10 A (I) = B (I) + 3 END DO