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The functions in this section perform miscellaneous but common operations that are awkward to express with C operators. On some processors these functions can use special machine instructions to perform these operations faster than the equivalent C code.

- Function:
*double***fmin***(double*¶`x`, double`y`) - Function:
*float***fminf***(float*¶`x`, float`y`) - Function:
*long double***fminl***(long double*¶`x`, long double`y`) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The

`fmin`

function returns the lesser of the two values`x`and`y`. It is similar to the expression((x) < (y) ? (x) : (y))

except that

`x`and`y`are only evaluated once.If an argument is NaN, the other argument is returned. If both arguments are NaN, NaN is returned.

- Function:
*double***fmax***(double*¶`x`, double`y`) - Function:
*float***fmaxf***(float*¶`x`, float`y`) - Function:
*long double***fmaxl***(long double*¶`x`, long double`y`) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The

`fmax`

function returns the greater of the two values`x`and`y`.If an argument is NaN, the other argument is returned. If both arguments are NaN, NaN is returned.

- Function:
*double***fminmag***(double*¶`x`, double`y`) - Function:
*float***fminmagf***(float*¶`x`, float`y`) - Function:
*long double***fminmagl***(long double*¶`x`, long double`y`) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

These functions, from TS 18661-1:2014, return whichever of the two values

`x`and`y`has the smaller absolute value. If both have the same absolute value, or either is NaN, they behave the same as the`fmin`

functions.

- Function:
*double***fmaxmag***(double*¶`x`, double`y`) - Function:
*float***fmaxmagf***(float*¶`x`, float`y`) - Function:
*long double***fmaxmagl***(long double*¶`x`, long double`y`) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

These functions, from TS 18661-1:2014, return whichever of the two values

`x`and`y`has the greater absolute value. If both have the same absolute value, or either is NaN, they behave the same as the`fmax`

functions.

- Function:
*double***fdim***(double*¶`x`, double`y`) - Function:
*float***fdimf***(float*¶`x`, float`y`) - Function:
*long double***fdiml***(long double*¶`x`, long double`y`) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The

`fdim`

function returns the positive difference between`x`and`y`. The positive difference isif`x`-`y``x`is greater than`y`, and*0*otherwise.If

`x`,`y`, or both are NaN, NaN is returned.

- Function:
*double***fma***(double*¶`x`, double`y`, double`z`) - Function:
*float***fmaf***(float*¶`x`, float`y`, float`z`) - Function:
*long double***fmal***(long double*¶`x`, long double`y`, long double`z`) -
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The

`fma`

function performs floating-point multiply-add. This is the operation*(*, but the intermediate result is not rounded to the destination type. This can sometimes improve the precision of a calculation.`x`·`y`) +`z`This function was introduced because some processors have a special instruction to perform multiply-add. The C compiler cannot use it directly, because the expression ‘

`x*y + z`’ is defined to round the intermediate result.`fma`

lets you choose when you want to round only once.On processors which do not implement multiply-add in hardware,

`fma`

can be very slow since it must avoid intermediate rounding.`math.h`defines the symbols`FP_FAST_FMA`

,`FP_FAST_FMAF`

, and`FP_FAST_FMAL`

when the corresponding version of`fma`

is no slower than the expression ‘`x*y + z`’. In the GNU C Library, this always means the operation is implemented in hardware.

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