# fimf-absolute-error, Qimf-absolute-error

Defines the maximum allowable absolute error for math library function results.

## Syntax

Linux: | -fimf-absolute-error=value[:funclist]

macOS: | -fimf-absolute-error=value[:funclist]

Windows: | /Qimf-absolute-error:value[:funclist]

Optional argument funclist is not supported for ifx.

## Arguments

value | Is a positive, floating-point number. Errors in math library function results may exceed the maximum relative error (max-error) setting if the absolute-error is less than or equal to value. The format for the number is [digits] [.digits] [ { e | E }[sign]digits]
funclist | Is an optional list of one or more math library functions to which the attribute should be applied. Do not specify the standard Fortran name of the math function; you must specify the actual math library name. If you specify more than one function, they must be separated with commas. Precision-specific variants like sin and sinf are considered different functions, so you would need to use -fimf-absolute-error=0.00001:sin,sinf (or /Qimf-absolute-error:0.00001:sin,sinf) to specify the maximum allowable absolute error for both the single-precision and double-precision sine functions. You also can specify the symbol /f to denote single-precision divides, symbol / to denote double-precision divides, symbol /l to denote extended-precision divides, and symbol /q to denote quad-precision divides. For example you can specify -fimf-absolute-error=0.00001:/ or /Qimf-absolute-error: 0.00001:/.

## Default

Zero ("0") | An absolute-error setting of 0 means that the function is bound by the relative error setting. This is the default behavior.

## Description

This option defines the maximum allowable absolute error for math library function results.

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

This option only affects functions that have zero as a possible return value, such as log, sin, asin, etc.

The relative error requirements for a particular function are determined by options that set the maximum relative error (max-error) and precision. The return value from a function must have a relative error less than the max-error value, or an absolute error less than the absolute-error value.

If you need to define the accuracy for a math function of a certain precision, specify the function name of the precision that you need. For example, if you want double precision, you can specify :sin; if you want single precision, you can specify :sinf, as in -fimf-absolute-error=0.00001:sin or /Qimf-absolute-error:0.00001:sin, or -fimf-absolute-error=0.00001:sqrtf or /Qimf-absolute-error:0.00001:sqrtf.

If you do not specify any function names, then the setting applies to all functions (and to all precisions). However, as soon as you specify an individual function name, the setting applies only to the function of corresponding precision. So, for example, sinf applies only to the single-precision sine function, sin applies only to the double-precision sine function, sinl applies only to the extended-precision sine function, etc.

### 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.

### Note

The standard Fortran names for the various math intrinsic functions do not match the math library names of the math intrinsic functions. You must find the actual math library name that is generated for the relevant Fortran math intrinsic.

One way to do this is to generate assembly code by using one of the following options:

Linux and macOS

-S

Windows

/Fa or /S

The assembly code will show the actual math library name.

For example, if you create a program that contains a call to SIN(x) where x is declared as REAL(KIND=4) and then use option S to produce assembly code for the program, the assembly code will show a call to sinf.

To define the maximum allowable absolute error for the single-precision sine function, you should specify:

Linux and macOS

-fimf-absolute-error=sinf

Windows

/Qimf-absolute-error:sinf

### Note

This option only applies to host compilation. When offloading is enabled, it does not impact device-specific compilation. Offloading can only be enabled when using ifx.

Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex. Notice revision #20201201

## IDE Equivalent

None

## Alternate Options

None

Parent topic: Floating-Point Options

## See Also

fimf-accuracy-bits, Qimf-accuracy-bits compiler option
fimf-arch-consistency, Qimf-arch-consistency compiler option
fimf-domain-exclusion, Qimf-domain-exclusion compiler option
fimf-max-error, Qimf-max-error compiler option
fimf-precision, Qimf-precision compiler option
fimf-use-svml_Qimf-use-svml compiler option