## Linux and UNIX Man Pages

Test Your Knowledge in Computers #679
Difficulty: Medium
IEEE 802.3 CSMA/CD, CSMA/CD stands for Carrier Sense, Multiple Authorization with Collision Detection.
True or False?

# fma(3m) [sunos man page]

```fma(3M) 						  Mathematical Library Functions						   fma(3M)

NAME
fma, fmaf, fmal - floating-point multiply-add

SYNOPSIS
cc [ flag... ] file... -lm [ library... ]
#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);

DESCRIPTION
These  functions compute (x * y) + z, rounded as one ternary operation. They compute the value (as if) to infinite precision and round once
to the result format, according to the rounding mode characterized by the value of FLT_ROUNDS.

RETURN VALUES
Upon successful completion, these functions return (x * y) + z, rounded as one ternary operation.

If x or y are NaN, a NaN is returned.

If x multiplied by y is an exact infinity and z is also an infinity but with the opposite  sign,  a  domain  error  occurs  and	a  NaN	is
returned.

If one of x and y is infinite, the other is 0, and z is not a NaN, a domain error occurs and a NaN is returned.

If x*y is not 0*Inf nor Inf*0 and z is a NaN, a NaN is returned.

ERRORS
These functions will fail if:

Domain Error    The value of x*y+z is invalid or the value x*y is invalid.

If  the	integer  expression  (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception will be
raised.

Range Error     The result overflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point  exception  will	be
raised.

USAGE
An  application	wanting  to  check  for  exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception  has  been  raised.  An  application  should
either examine the return value or check the floating point exception flags to detect exceptions.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

SunOS 5.10							    20 Sep 2004 							   fma(3M)```

## Check Out this Related Man Page

```FMA(P)							     POSIX Programmer's Manual							    FMA(P)

NAME
fma, fmaf, fmal - floating-point multiply-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);

DESCRIPTION
These functions shall compute (x * y) + z, rounded as one ternary operation: they shall compute the value (as if) to infinite precision and
round once to the result format, according to the rounding mode characterized by the value of FLT_ROUNDS.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
has occurred.

RETURN VALUE
Upon successful completion, these functions shall return (x * y) + z, rounded as one ternary operation.

If x or y are NaN, a NaN shall be returned.

If x multiplied by y is an exact infinity and z is also an infinity but with the opposite sign, a domain error shall occur,  and  either  a
NaN (if supported), or an implementation-defined value shall be returned.

If  one	of  x and y is infinite, the other is zero, and z is not a NaN, a domain error shall occur, and either a NaN (if supported), or an
implementation-defined value shall be returned.

If one of x and y is infinite, the other is zero, and z is a NaN, a NaN shall be returned and a domain error may occur.

If x* y is not 0*Inf nor Inf*0 and z is a NaN, a NaN shall be returned.

ERRORS
These functions shall fail if:

Domain Error
The value of x* y+ z is invalid, or the value x* y is invalid and z is not a NaN.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall	be  set  to  [EDOM].  If  the  integer	expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

Range Error
The result overflows.

If  the	integer  expression  (math_errhandling	&  MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

These functions may fail if:

Domain Error
The value x* y is invalid and z is a NaN.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall	be  set  to  [EDOM].  If  the  integer	expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

Range Error
The result underflows.

If  the	integer  expression  (math_errhandling	&  MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of  each  other,  but	at
least one of them must be non-zero.

RATIONALE
In  many  cases, clever use of floating (fused) multiply-add leads to much improved code; but its unexpected use by the compiler can under-
mine carefully written code. The FP_CONTRACT macro can be used to disallow use of floating multiply-add; and the fma() function	guarantees
its  use  where desired. Many current machines provide hardware floating multiply-add instructions; software implementation can be used for
others.

FUTURE DIRECTIONS
None.