Visible to Intel only — GUID: GUID-ED16469A-8183-4F24-A7FA-2898C6F9DC40
Visible to Intel only — GUID: GUID-ED16469A-8183-4F24-A7FA-2898C6F9DC40
GAP Message (Diagnostic ID 30513)
Message
Insert a "%s ivdep" statement right before the loop at line %d to vectorize the loop.
Advice
Add "!DIR$ IVDEP" before the specified loop. This directive enables the vectorization of the loop at the specified line by ignoring some of the assumed cross-iteration data dependencies.
Example
Consider the following:
subroutine foo(a, m, n)
integer m, n
real a(n)
do i=1,n
a(i) = a(i+m) + 1
enddo
end
In this case, the compiler is unable to vectorize the loop because m could be -1, where each iteration is dependent on the previous iteration. If m is known to be positive, you can vectorize this loop.
If you determine it is safe to do so, you can add the directive as follows:
subroutine foo(a, m, n)
integer m, n
real a(n)
!dir$ ivdep
do i=1,n
a(i) = a(i+m) + 1
enddo
end
Verify
Confirm that any arrays in the loop do not have unsafe cross-iteration dependencies. A cross-iteration dependency exists if a memory location is modified in an iteration of the loop and accessed by a fetch or store operation in another iteration of the loop. Make sure that there are no such dependencies, or that any cross-iteration dependencies can be safely ignored.