Developer Guide and Reference

Contents

fimf-arch-consistency, Qimf-arch-consistency

Ensures that the math library functions produce consistent results across different microarchitectural implementations of the same architecture.
This content is specific to C++; it does not apply to
DPC++
.

Syntax

Linux:
-fimf-arch-consistency
=
value
[
:
funclist
]
Windows:
/Qimf-arch-consistency
:
value
[
:
funclist
]
Arguments
value
Is one of the logical values "true" or "false".
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-arch-consistency=true:sin,sinf
(or
/Qimf-arch-consistency:true:sin,sinf
) to specify consistent results 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-arch-consistency=true:/
or
/Qimf-arch-consistency:true:/
.
Default
false
Implementations of some math library functions may produce slightly different results on implementations of the same architecture.
Description
This option ensures that the math library functions produce consistent results across different microarchitectural implementations of the same architecture (for example, across different microarchitectural implementations of IA-32 architecture). Consistency is only guaranteed for a single binary. Consistency is not guaranteed across different architectures. For example, consistency is not guaranteed across IA-32 architecture and Intel® 64 architecture.
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-arch-consistency=true:sin
or
/Qimf-arch-consistency:true:sin
, or
-fimf-arch-consistency=false:sqrtf
or
/Qimf-arch-consistency:false: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.
The
-fimf-arch-consistency
(Linux*) and
/Qimf-arch-consistency
(Windows*) option may decrease run-time performance, but the option will provide bit-wise consistent results on all Intel® processors and compatible, non-Intel processors, regardless of micro-architecture. This option may not provide bit-wise consistent results between different architectures.
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.
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

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.