Using fastmath math routines

Header File

fastmath.h

Category

Math Routines

Description

The FastMath routines are high performance math routines that don't check for most error conditions and never call matherr. They are coded for maximum speed. These functions are never exported from the RTLDLL, which means that they always get linked directly into the PE file that is being created.

When you include fastmath.h, the following math functions are remapped to these fastmath functions.

Math Routine	Fastmath Routine	Math Routine	Fastmath Routine
acos	_fm_acos	asin	_fm_asin
atan	_fm_atan	atan2	_fm_atan2
cos	_fm_cos	cosh	_fm_cosh
exp	_fm_exp	fabs	_fm_fabs
asin	_fm_asin	atan	_fm_atan
atan2	_fm_atan2	cos	_fm_cos
cosh	_fm_cosh	exp	_fm_exp
fabs	_fm_fabs	frexp	_fm_frexp
hypot	_fm_hypot	ldexp	_fm_ldexp
log	_fm_log	log10	_fm_log10
sin	_fm_sin	sinh	_fm_sinh
sqrt	_fm_sqr	tan	_fm_tan
tanh	_fm_tanh	sincos	_fm_sincos
acosl	_fm_acosl	asinl	_fm_asinl
atan2l	_fm_atan2l	atanl	_fm_atanl
coshl	_fm_coshl	cosl	_fm_cosl
expl	_fm_expl	fabsl	_fm_fabsl
frexpl	_fm_frexpl	hypotl	_fm_hypotl
ldexpl	_fm_ldexpl	log10l	_fm_log10l
logl	_fm_logl	sinhl	_fm_sinhl
sinl	_fm_sinl	sqrtl	_fm_sqrtl
tanhl	_fm_tanhl	tanl	_fm_tanl
sincosl	_fm_sincosl	atanhl	_fm_atanhl
acoshl	_fm_acoshl	asinhl	_fm_asinhl

If you don't want the standard C function names remapped to the FastMath versions, then define _FM_NO_REMAP. The FastMath routines can still be called with their _fm_xxx names.

The following additional functions are available in FastMath; they are not directly supported in the regular RTL:

void _FMAPI _fm_sincos(double __a, double *__x, double *__y);

void _FMAPI _fm_sincosl(long double __a, long double *__x, long double *__y);

long double _FMAPI _fm_atanhl (long double __x);

long double _FMAPI _fm_acoshl (long double __x);

long double _FMAPI _fm_asinhl (long double __x);

__inline void _fm_fwait(void)

unsigned int _FMAPI _fm_init(void);

_fm_fwait is a special inline function that performs an intrinsic FWAIT instruction.

_Fm_init is a function that can be called to mask all fpu exceptions prior to using the FastMath routines.

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