Developer Guide and Reference

Contents

novector

Specifies that a particular loop should never be vectorized.

Syntax

#pragma novector
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.
Example: Using the
novector
pragma
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.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804