Defines the maximum allowable absolute error for math library function results.
Syntax
Linux OS and OS X: | -fimf-absolute-error=value[:funclist] |
Windows OS: | /Qimf-absolute-error:value[:funclist] |
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. 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.
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 |