Average Error: 11.4 → 0.1
Time: 3.2s
Precision: binary64
\[x - \frac{\left(y \cdot 2\right) \cdot z}{\left(z \cdot 2\right) \cdot z - y \cdot t}\]
↓
\[x - \frac{1}{\frac{z}{y} - \frac{t}{z \cdot 2}}\]
x - \frac{\left(y \cdot 2\right) \cdot z}{\left(z \cdot 2\right) \cdot z - y \cdot t}
↓
x - \frac{1}{\frac{z}{y} - \frac{t}{z \cdot 2}}
(FPCore (x y z t)
 :precision binary64
 (- x (/ (* (* y 2.0) z) (- (* (* z 2.0) z) (* y t)))))
↓
(FPCore (x y z t)
 :precision binary64
 (- x (/ 1.0 (- (/ z y) (/ t (* z 2.0))))))
double code(double x, double y, double z, double t) {
	return x - (((y * 2.0) * z) / (((z * 2.0) * z) - (y * t)));
}
↓
double code(double x, double y, double z, double t) {
	return x - (1.0 / ((z / y) - (t / (z * 2.0))));
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Bits error versus t

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original11.4
Target0.1
Herbie0.1
\[x - \frac{1}{\frac{z}{y} - \frac{\frac{t}{2}}{z}}\]

Derivation

  1. Initial program 11.4

    \[x - \frac{\left(y \cdot 2\right) \cdot z}{\left(z \cdot 2\right) \cdot z - y \cdot t}\]

  2. Simplified2.8

    \[\leadsto \color{blue}{x - \frac{y}{z - \frac{y \cdot t}{2 \cdot z}}}\]
  3. Using strategy rm

  4. Applied clear-num_binary642.8

    \[\leadsto x - \color{blue}{\frac{1}{\frac{z - \frac{y \cdot t}{2 \cdot z}}{y}}}\]

  5. Simplified2.8

    \[\leadsto x - \frac{1}{\color{blue}{\frac{z - \frac{y \cdot t}{z \cdot 2}}{y}}}\]
  6. Using strategy rm

  7. Applied div-sub_binary642.8

    \[\leadsto x - \frac{1}{\color{blue}{\frac{z}{y} - \frac{\frac{y \cdot t}{z \cdot 2}}{y}}}\]

  8. Simplified0.1

    \[\leadsto x - \frac{1}{\frac{z}{y} - \color{blue}{\frac{t}{z \cdot 2}}}\]

  9. Final simplification0.1

    \[\leadsto x - \frac{1}{\frac{z}{y} - \frac{t}{z \cdot 2}}\]

Reproduce

herbie shell --seed 2020233 
(FPCore (x y z t)
  :name "Numeric.AD.Rank1.Halley:findZero from ad-4.2.4"
  :precision binary64

  :herbie-target
  (- x (/ 1.0 (- (/ z y) (/ (/ t 2.0) z))))

  (- x (/ (* (* y 2.0) z) (- (* (* z 2.0) z) (* y t)))))