# FMA

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

VERSIONS

ATTRIBUTES

CONFORMING TO

SEE ALSO

COLOPHON

## 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***);**

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

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

For an
explanation of the terms used in this section, see
**attributes**(7).

## CONFORMING TO

C99,
POSIX.1-2001.

## SEE ALSO

**remainder**(3),
**remquo**(3)

## COLOPHON

This page is
part of release 3.53 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/.