HP-UX Reference (11i v2 07/12) - 3 Library Functions A-M (vol 6)

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fma(3M) fma(3M)

(Itanium(R)-based System Only)

NAME

fma(), fmaf( ), fmaw( ), fmal(), fmaq() - ﬂoating multiply-add functions

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);

extended fmaw(extended x, extended y, extended z);

quad fmaq(quad x, quad y, quad z);

DESCRIPTION

fma() returns (x*y)+z, rounded as one ternary operation: it computes the value (as if) to inﬁnite preci-

sion and rounds once to the result format, according to the current rounding mode.

fmaf() is a float version of fma(); it takes float arguments and returns a float result.

fmal() is a long double version of fma(); it takes long double arguments and returns a

long

double

result.

fmaw() is an extended version of fma(); it takes extended arguments and returns an extended

result.

fmaq() is equivalent to fmal() on HP-UX systems.

The FP_FAST_FMA , FP_FAST_FMAF , and FP_FAST_FMAW macros are deﬁned in <math.h>, indicat-

ing that

fma(), fmaf(), and fmaw() are each as fast as a multiply and add.

USAGE

These functions are available only for Itanium-based systems.

To use these functions, compile either with the default -Ae option or with the -Aa

and

-D_HPUX_SOURCE options.

To use fmaw() or fmaq(), compile also with the -fpwidetypes option.

To use these functions, make sure your program includes <math.h>. Link in the math library by specify-

ing -lm on the compiler or linker command line.

RETURN VALUE

If one of x and y is inﬁnite, the other is zero, and z is a NaN,

fma() returns NaN and optionally raises the

invalid exception.

If one of x and y is inﬁnite, the other is zero, and z is not a NaN,

fma() returns NaN and raises the invalid

exception.

If x times y is an exact inﬁnity and z is also an inﬁnity but with the opposite sign,

fma() returns NaN and

raises the invalid exception.

fma() returns a properly signed inﬁnity in lieu of a value whose magnitude is too large, and raise the

overﬂow and inexact exceptions.

fma() raises the underﬂow and inexact exceptions whenever a result is tiny (essentially denormal or zero)

and thereby suffers loss of accuracy, and may raise those exceptions if the result is merely tiny.

fma() raises the inexact exception whenever a rounded result does not equal the mathematical result.

ERRORS

No errors are deﬁned.