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fma

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

fma, fmaf, fmal - floatin-point multiply and add

LIBRARY

Math library (libm,~-lm)

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: I]x * y + z] or I]x * y] is invalid.: An invalid floatin-point exception (FE_INVALID) is raised.
Range error: result overflow: An overflow floatin-point exception (FE_OVERFLOW) is raised.
Range error: result underflow: An underflow floatin-point exception (FE_UNDERFLOW) is raised. These functions do not set errno.

ATTRIBUTES

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

Interface	Attribute	Value
fma(), fmaf(), fmal()	Thread safety	M-Safe

STANDARDS

C11, POSIX.-2008.

HISTORY

glibc 2.1. C99, POSIX.-2001.