Developer Guide and Reference

Contents

prec-div, Qprec-div

Improves precision of floating-point divides.

Syntax

Linux and macOS:
-prec-div
-no-prec-div
Windows:
/Qprec-div
/Qprec-div-
Arguments
None
Default
OFF
Default heuristics are used. The default is not as accurate as full IEEE division, but it is slightly more accurate than would be obtained when
/Qprec-div-
or
-no-prec-div
is specified.
If you need full IEEE precision for division, you should specify
[Q]prec-div
.
Description
This option improves precision of floating-point divides. It has a slight impact on speed.
At default optimization levels, the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, use this option to disable the floating-point division-to-multiplication optimization. The result is more accurate, with some loss of performance.
If you specify
-no-prec-div
(Linux* and
macOS*
) or
/Qprec-div-
(Windows*), it enables optimizations that give slightly less precise results than full IEEE division.
Option
[Q]prec-div
is implied by option
-fp-model precise
(Linux* and
macOS*
) and option
/fp:precise
(Windows*).
Alternate Options
None

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