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Miscellaneous FP arithmetic functions

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.

double fmin (double x, double y) Function
float fminf (float x, float y) Function
long double fminl (long double x, long double y) Function
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.

double fmax (double x, double y) Function
float fmaxf (float x, float y) Function
long double fmaxl (long double x, long double y) Function
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.

double fdim (double x, double y) Function
float fdimf (float x, float y) Function
long double fdiml (long double x, long double y) Function
The fdim function returns the positive difference between x and y. The positive difference is x - y if x is greater than y, and 0 otherwise.

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

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) Function
The fma function performs floating-point multiply-add. This is the operation (x &middot; y) + z, but the intermediate result is not rounded to the destination type. This can sometimes improve the precision of a calculation.

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.