fma (3)
Leading comments
Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
<mtk.manpages@gmail.com>
%%%LICENSE_START(GPL_NOVERSION_ONELINE)
Distributed under GPL
%%%LICENSE_END
Modified 2004-11-15, Added further text on FLT_ROUNDS
as suggested by AEB and Fabian Kreutz
NAME
fma, fmaf, fmal - floating-point multiply and addSYNOPSIS
#include <math.h> double fma(double x, double y, double z);
float fmaf(float x, float y, float z);
long double fmal(long double x, long double y, long double z);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fma(), fmaf(), fmal():
-
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTION
These functions compute x * y + z. The result is rounded as one ternary operation according to the current rounding mode (see fenv(3)).RETURN VALUE
These functions return the value of x * y + z, rounded as one ternary operation.If x or y is a NaN, a NaN is returned.
If x times y is an exact infinity, and z is an infinity with the opposite sign, a domain error occurs, and a NaN is returned.
If one of x or y is an infinity, the other is 0, and z is not a NaN, a domain error occurs, and a NaN is returned.
If one of x or y is an infinity, and the other is 0, and z is a NaN, a domain error occurs, and a NaN is returned.
If x times y is not an infinity times zero (or vice versa), and z is a NaN, a NaN is returned.
If the result overflows, a range error occurs, and an infinity with the correct sign is returned.
If the result underflows, a range error occurs, and a signed 0 is returned.
ERRORS
See math_error(7) for information on how to determine whether an error has occurred when calling these functions.The following errors can occur:
- Domain error: x * y + z, or x * y is invalid and z is not a NaN
- An invalid floating-point exception (FE_INVALID) is raised.
- Range error: result overflow
- An overflow floating-point exception (FE_OVERFLOW) is raised.
- Range error: result underflow
- An underflow floating-point exception (FE_UNDERFLOW) is raised.
These functions do not set errno.
VERSIONS
These functions first appeared in glibc in version 2.1.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| fma(), fmaf(), fmal() | Thread safety | MT-Safe |