## SYNOPSIS

`
#include <math.h>
`

`
float
fmaf(float x, float y, float z)
`

`
double
fma(double x, double y, double z)
`

## DESCRIPTION

The ` fma()`, and

`functions return (x * y) + z, computed with only one rounding error. Using the ordinary multiplication and addition operators, by contrast, results in two roundings: one for the intermediate product and one for the final result.`fmaf()

For instance, the expression 1.2e100 * 2.0e208 - 1.4e308 produces infinity
due to overflow in the intermediate product, whereas ` fma()`(1.2e100,
2.0e208, -1.4e308) returns approximately 1.0e308.

The fused multiply-add operation is often used to improve the accuracy of
calculations such as dot products. It may also be used to improve performance
on machines that implement it natively. The macros `FP_FAST_FMA`,
`FP_FAST_FMAF` and `FP_FAST_FMAL` may be defined in <math.h> to indicate that
` fma()`, and

`(respectively) have comparable or faster speed than a multiply operation followed by an add operation.`fmaf()

## CONFORMANCE

` fma()` and

`functions conform to ANSI/ISO 9899:1999 'ISO C99'.`fmaf()

## MULTITHREAD SAFETY LEVEL

MT-Safe.

## PORTING ISSUES

None.

## AVAILABILITY

PTC MKS Toolkit for Professional Developers

PTC MKS Toolkit for Professional Developers 64-Bit Edition

PTC MKS Toolkit for Enterprise Developers

PTC MKS Toolkit for Enterprise Developers 64-Bit Edition

## SEE ALSO

PTC MKS Toolkit 10.3 Documentation Build 39.