Average Error: 0.0 → 0.0
Time: 5.7s
Precision: binary64
\[x \cdot x - \left(y \cdot 4\right) \cdot z \]
↓
\[\mathsf{fma}\left(x, x, \left(y \cdot z\right) \cdot -4\right) \]
x \cdot x - \left(y \cdot 4\right) \cdot z
↓
\mathsf{fma}\left(x, x, \left(y \cdot z\right) \cdot -4\right)

(FPCore (x y z) :precision binary64 (- (* x x) (* (* y 4.0) z)))
↓
(FPCore (x y z) :precision binary64 (fma x x (* (* y z) -4.0)))
double code(double x, double y, double z) {
	return (x * x) - ((y * 4.0) * z);
}
↓
double code(double x, double y, double z) {
	return fma(x, x, ((y * z) * -4.0));
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Derivation

  1. Initial program 0.0

    \[x \cdot x - \left(y \cdot 4\right) \cdot z \]

  2. Simplified0.0

    \[\leadsto \color{blue}{\mathsf{fma}\left(-4, y \cdot z, x \cdot x\right)} \]

  3. Taylor expanded in y around 0 0.0

    \[\leadsto \color{blue}{{x}^{2} - 4 \cdot \left(y \cdot z\right)} \]

  4. Simplified0.0

    \[\leadsto \color{blue}{\mathsf{fma}\left(x, x, \left(y \cdot z\right) \cdot -4\right)} \]

  5. Final simplification0.0

    \[\leadsto \mathsf{fma}\left(x, x, \left(y \cdot z\right) \cdot -4\right) \]

Reproduce

herbie shell --seed 2021340 
(FPCore (x y z)
  :name "Graphics.Rasterific.QuadraticFormula:discriminant from Rasterific-0.6.1"
  :precision binary64
  (- (* x x) (* (* y 4.0) z)))