C++ How to use the fma() function and examples

C++ Library Function <cmath>

The fma() function takes three parameters x, y, and z, and returns x * y + z without losing precision

This function in<cmath>Defined in the header file.

fma() prototype [from C ++ 11Standard starts]

double fma(double x, double y, double z);
float fma(float x, float y, float z);
long double fma(long double x, long double y, long double z);　
Promoted fma(Type1　x, Type2　y, Type z);　//　Used for the combination of arithmetic types

From C ++ 11Starting from C, if the parameters passed to fma() are long double, the returned type is promoted to long double. If not, the returned type is promoted to double.

[Math] x*y+z = fma(x, y, z) [C++　Language]

fma() parameters

fma() accepts three parameters.

• x -The first parameter to be multiplied.

• y -The second parameter to be multiplied by x.

• z -The third parameter to be added to the product of x and y.

fma() return value

The return value of the fma() function x*y+z is rounded once to fit the result type, just like the calculated precision.

Example: How does fma() work?

#include <cmath>
using namespace std;
int main()
{
　　　　double x =　2.0, y =　3.1, z =　3.0, result;
　　　　result = fma(x, y, z);
　　　　cout << "fma(x, y, z) = " << result << endl;
　　　　long double xLD =　3.4, resultLD;
　　　　resultLD = fma(xLD, y, z);
　　　　cout << "fma(xLD, y, z) = " << resultLD << endl;
　　　　return 0;
}

The output when running the program is:

fma(x, y, z) =　9.2
fma(xLD, y, z) =　13.54

C++ Library Function <cmath>