fimf-accuracy-bits, Qimf-accuracy-bits

Defines the relative error for math library function results.

IDE Equivalent

None

Architectures

IA-32, Intel® 64 architectures

Syntax

Linux and Mac OS X:

-fimf-accuracy-bits=bits[:funclist]

Windows:

/Qimf-accuracy-bits:bits[:funclist]

Arguments

`bits`	Is a positive, floating-point number indicating the number of correct bits the compiler should use.
`funclist`	Is an optional list of one or more math library functions to which the attribute should be applied. If you specify more than one function, they must be separated with commas.

Default

OFF	The compiler uses default heuristics when calling math library functions.

Description

This option defines the relative error, measured by the number of correct bits, for math library function results.

The following formula is used to convert bits into ulps: ulps = 2^p-1-bits, where p is the number of the target format mantissa bits (24, 53, and 64 for single, double, and long double, respectively).

This option can improve run-time performance, but it may decrease the accuracy of results.

If option -fimf-precision (Linux* OS and Mac OS* X) or /Qimf-precision (Windows* OS), or option -fimf-max-error (Linux* OS and Mac OS* X) or /Qimf-max-error (Windows* OS), or option -fimf-accuracy-bits (Linux OS and Mac OS* X) or /Qimf-accuracy-bits (Windows OS) is specified, the default value for max-error is determined by that option. If one or more of these options are specified, the default value for max-error is determined by the last one specified on the command line.

If none of these options are specified, the default value for max-error is determined by the setting specified for option-[no-]fast-transcendentals (Linux OS and Mac OS X) or /Qfast-transcendentals[-] (Windows OS). If that option also has not been specified, the default value is determined by the setting of option -fp-model (Linux OS and Mac OS X) or /fp (Windows OS).

Note

Many routines in libraries LIBM (Math Library) and SVML (Short Vector Math Library) are more highly optimized for Intel® microprocessors than for non-Intel microprocessors.

Alternate Options