Name
fma, fmaf, fmal — floating-point multiply and
add

Synopsis
#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 `)`

;

Note
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`

Note
Link with `−lm`

.

DESCRIPTION
The `fma`

() function computes
`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
Multithreading (see pthreads(7))
The `fma`

(), `fmaf`

(), and `fmal`

() functions are thread-safe.

CONFORMING TO
C99, POSIX.1-2001.

COLOPHON
This page is part of release 3.54 of the Linux `man-pages`

project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man−pages/.

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