novector

Syntax

Arguments

None

Description

The novector pragma specifies that a particular loop should never be vectorized, even if it is legal to do so. When avoiding vectorization of a loop is desirable (when vectorization results in a performance regression rather than improvement), the novector pragma can be used in the source text to disable vectorization of a loop. This behavior is in contrast to the vector always pragma.

The novector pragma is supported in host code only.

void foo(int lb, int ub) {
  #pragma novector
  for(j=lb; j<ub; j++) { a[j]=a[j]+b[j]; } 
}

When the trip count (ub - lb) is too low to make vectorization worthwhile, you can use the novector pragma to tell the compiler not to vectorize, even if the loop is considered vectorizable.