# fma(3) — Linux manual page

```fma(3)                  Library Functions Manual                  fma(3)
```

## NAME         top

```       fma, fmaf, fmal - floating-point multiply and add
```

## LIBRARY         top

```       Math library (libm, -lm)
```

## SYNOPSIS         top

```       #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         top

```       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         top

```       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         top

```       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.
```

## ATTRIBUTES         top

```       For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface                           │ Attribute     │ Value   │
├─────────────────────────────────────┼───────────────┼─────────┤
│ fma(), fmaf(), fmal()               │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## STANDARDS         top

```       C11, POSIX.1-2008.
```

## HISTORY         top

```       glibc 2.1.  C99, POSIX.1-2001.
```

```       remainder(3), remquo(3)