Average Error: 19.9 → 0.0
Time: 1.2m
Precision: 64
Internal Precision: 128
\[\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}\]
\[\sqrt[3]{\frac{x + y}{\sqrt{x^2 + y^2}^*} \cdot \left({\left(\frac{x - y}{\sqrt{x^2 + y^2}^*}\right)}^{3} \cdot \left(\frac{x + y}{\sqrt{x^2 + y^2}^*} \cdot \frac{x + y}{\sqrt{x^2 + y^2}^*}\right)\right)}\]

Error

Bits error versus x

Bits error versus y

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original19.9
Target0.0
Herbie0.0
\[\begin{array}{l} \mathbf{if}\;0.5 \lt \left|\frac{x}{y}\right| \lt 2:\\ \;\;\;\;\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}\\ \mathbf{else}:\\ \;\;\;\;1 - \frac{2}{1 + \frac{x}{y} \cdot \frac{x}{y}}\\ \end{array}\]

Derivation

  1. Initial program 19.9

    \[\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}\]
  2. Simplified19.9

    \[\leadsto \color{blue}{\frac{\left(x - y\right) \cdot \left(y + x\right)}{(x \cdot x + \left(y \cdot y\right))_*}}\]
  3. Using strategy rm
  4. Applied add-sqr-sqrt19.9

    \[\leadsto \frac{\left(x - y\right) \cdot \left(y + x\right)}{\color{blue}{\sqrt{(x \cdot x + \left(y \cdot y\right))_*} \cdot \sqrt{(x \cdot x + \left(y \cdot y\right))_*}}}\]
  5. Applied times-frac19.9

    \[\leadsto \color{blue}{\frac{x - y}{\sqrt{(x \cdot x + \left(y \cdot y\right))_*}} \cdot \frac{y + x}{\sqrt{(x \cdot x + \left(y \cdot y\right))_*}}}\]
  6. Simplified19.9

    \[\leadsto \color{blue}{\frac{x - y}{\sqrt{x^2 + y^2}^*}} \cdot \frac{y + x}{\sqrt{(x \cdot x + \left(y \cdot y\right))_*}}\]
  7. Simplified0.0

    \[\leadsto \frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \color{blue}{\frac{x + y}{\sqrt{x^2 + y^2}^*}}\]
  8. Using strategy rm
  9. Applied add-cbrt-cube31.4

    \[\leadsto \frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \frac{x + y}{\color{blue}{\sqrt[3]{\left(\sqrt{x^2 + y^2}^* \cdot \sqrt{x^2 + y^2}^*\right) \cdot \sqrt{x^2 + y^2}^*}}}\]
  10. Applied add-cbrt-cube31.4

    \[\leadsto \frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \frac{\color{blue}{\sqrt[3]{\left(\left(x + y\right) \cdot \left(x + y\right)\right) \cdot \left(x + y\right)}}}{\sqrt[3]{\left(\sqrt{x^2 + y^2}^* \cdot \sqrt{x^2 + y^2}^*\right) \cdot \sqrt{x^2 + y^2}^*}}\]
  11. Applied cbrt-undiv31.4

    \[\leadsto \frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \color{blue}{\sqrt[3]{\frac{\left(\left(x + y\right) \cdot \left(x + y\right)\right) \cdot \left(x + y\right)}{\left(\sqrt{x^2 + y^2}^* \cdot \sqrt{x^2 + y^2}^*\right) \cdot \sqrt{x^2 + y^2}^*}}}\]
  12. Applied add-cbrt-cube31.4

    \[\leadsto \color{blue}{\sqrt[3]{\left(\frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \frac{x - y}{\sqrt{x^2 + y^2}^*}\right) \cdot \frac{x - y}{\sqrt{x^2 + y^2}^*}}} \cdot \sqrt[3]{\frac{\left(\left(x + y\right) \cdot \left(x + y\right)\right) \cdot \left(x + y\right)}{\left(\sqrt{x^2 + y^2}^* \cdot \sqrt{x^2 + y^2}^*\right) \cdot \sqrt{x^2 + y^2}^*}}\]
  13. Applied cbrt-unprod31.4

    \[\leadsto \color{blue}{\sqrt[3]{\left(\left(\frac{x - y}{\sqrt{x^2 + y^2}^*} \cdot \frac{x - y}{\sqrt{x^2 + y^2}^*}\right) \cdot \frac{x - y}{\sqrt{x^2 + y^2}^*}\right) \cdot \frac{\left(\left(x + y\right) \cdot \left(x + y\right)\right) \cdot \left(x + y\right)}{\left(\sqrt{x^2 + y^2}^* \cdot \sqrt{x^2 + y^2}^*\right) \cdot \sqrt{x^2 + y^2}^*}}}\]
  14. Simplified0.0

    \[\leadsto \sqrt[3]{\color{blue}{{\left(\frac{y + x}{\sqrt{x^2 + y^2}^*}\right)}^{3} \cdot {\left(\frac{x - y}{\sqrt{x^2 + y^2}^*}\right)}^{3}}}\]
  15. Using strategy rm
  16. Applied cube-mult0.0

    \[\leadsto \sqrt[3]{\color{blue}{\left(\frac{y + x}{\sqrt{x^2 + y^2}^*} \cdot \left(\frac{y + x}{\sqrt{x^2 + y^2}^*} \cdot \frac{y + x}{\sqrt{x^2 + y^2}^*}\right)\right)} \cdot {\left(\frac{x - y}{\sqrt{x^2 + y^2}^*}\right)}^{3}}\]
  17. Applied associate-*l*0.0

    \[\leadsto \sqrt[3]{\color{blue}{\frac{y + x}{\sqrt{x^2 + y^2}^*} \cdot \left(\left(\frac{y + x}{\sqrt{x^2 + y^2}^*} \cdot \frac{y + x}{\sqrt{x^2 + y^2}^*}\right) \cdot {\left(\frac{x - y}{\sqrt{x^2 + y^2}^*}\right)}^{3}\right)}}\]
  18. Final simplification0.0

    \[\leadsto \sqrt[3]{\frac{x + y}{\sqrt{x^2 + y^2}^*} \cdot \left({\left(\frac{x - y}{\sqrt{x^2 + y^2}^*}\right)}^{3} \cdot \left(\frac{x + y}{\sqrt{x^2 + y^2}^*} \cdot \frac{x + y}{\sqrt{x^2 + y^2}^*}\right)\right)}\]

Reproduce

herbie shell --seed 2019030 +o rules:numerics
(FPCore (x y)
  :name "Kahan p9 Example"
  :pre (and (< 0 x 1) (< y 1))

  :herbie-target
  (if (< 0.5 (fabs (/ x y)) 2) (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))) (- 1 (/ 2 (+ 1 (* (/ x y) (/ x y))))))

  (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))))