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# fma(3)

2017-09-15
Aliases: fmaf(3), fmaf(3), fmaf(3), fmaf(3), fmaf(3), fmaf(3), fmal(3), fmal(3), fmal(3), fmal(3), fmal(3), fmal(3)

### manpages-dev

Manual pages about using GNU/Linux for development

### man-pages

Linux kernel and C library user-space interface documentation

## 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);
```
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fma(), fmaf(), fmal():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

## 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 Thread safety MT-Safe

## CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.