fp-model, fp

-fp-model precise or /fp:precise

Tells the compiler to strictly adhere to value-safe optimizations when implementing floating-point calculations. It disables optimizations that can change the result of floating-point calculations.

These semantics ensure the reproducibility of floating-point computations for serial code, including code vectorized or auto-parallelized by the compiler, but they may slow performance. They do not ensure value safety or run-to-run reproducibility of other parallel code. Run-to-run reproducibility for floating-point reductions in OpenMP* code may be obtained for a fixed number of threads through the KMP_DETERMINISTIC_REDUCTION environment variable. For more information about this environment variable, see topic "Supported Environment Variables".

The compiler assumes the default floating-point environment; you are not allowed to modify it.

Note that option fp-model precise is converted to fp-model source and option fp:precise is converted to fp:source.

Floating-point exception semantics are disabled by default. To enable these semantics, you must also specify -fp-model except or /fp:except.

Note that option fp-model precise enables option assume protect-parens, which tells the optimizer to honor parentheses in REAL and COMPLEX expression evaluations by not reassociating operations.

-fp-model fast[=1|2] or /fp:fast[=1|2]

Tells the compiler to use more aggressive optimizations when implementing floating-point calculations. These optimizations increase speed, but may affect the accuracy or reproducibility of floating-point computations.

Specifying fast is the same as specifying fast=1. fast=2 may produce faster and less accurate results.

Floating-point exception semantics are disabled by default and they cannot be enabled because you cannot specify fast and except together in the same compilation. To enable exception semantics, you must explicitly specify another keyword (see other keyword descriptions for details).

-fp-model strict or /fp:strict

Tells the compiler to strictly adhere to value-safe optimizations when implementing floating-point calculations and enables floating-point exception semantics. This is the strictest floating-point model.

The compiler does not assume the default floating-point environment; you are allowed to modify it.

Floating-point exception semantics can be disabled by explicitly specifying -fp-model no-except or /fp:except-.

-fp-model source or /fp:source

This option causes intermediate results to be rounded to the precision defined in the source code. It also implies keyword precise unless it is overridden by a keyword from Group A.

The compiler assumes the default floating-point environment; you are not allowed to modify it.

Note that option fp-model source enables option assume protect-parens, which tells the optimizer to honor parentheses in REAL and COMPLEX expression evaluations by not reassociating operations.

-fp-model except or /fp:except

Tells the compiler to follow strict floating-point exception semantics.