Average Error: 58.6 → 0.2
Time: 31.5s
Precision: 64
\[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)\]
\[(\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \left(\frac{\left({\left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right)}^{3} - 8\right) \cdot \varepsilon}{(2 \cdot \left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) + \left((\left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) \cdot \left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) + 4)_*\right))_*}\right))_*\]

Error

Bits error versus eps

Target

Original58.6
Target0.2
Herbie0.2
\[-2 \cdot \left(\left(\varepsilon + \frac{{\varepsilon}^{3}}{3}\right) + \frac{{\varepsilon}^{5}}{5}\right)\]

Derivation

  1. Initial program 58.6

    \[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)\]
  2. Taylor expanded around 0 0.2

    \[\leadsto \color{blue}{-\left(\frac{2}{3} \cdot {\varepsilon}^{3} + \left(\frac{2}{5} \cdot {\varepsilon}^{5} + 2 \cdot \varepsilon\right)\right)}\]
  3. Simplified0.2

    \[\leadsto \color{blue}{(\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \left(\varepsilon \cdot \left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon - 2\right)\right))_*}\]
  4. Using strategy rm
  5. Applied flip3--0.2

    \[\leadsto (\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \left(\varepsilon \cdot \color{blue}{\frac{{\left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right)}^{3} - {2}^{3}}{\left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) \cdot \left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) + \left(2 \cdot 2 + \left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) \cdot 2\right)}}\right))_*\]
  6. Applied associate-*r/0.2

    \[\leadsto (\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \color{blue}{\left(\frac{\varepsilon \cdot \left({\left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right)}^{3} - {2}^{3}\right)}{\left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) \cdot \left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) + \left(2 \cdot 2 + \left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right) \cdot 2\right)}\right)})_*\]
  7. Simplified0.2

    \[\leadsto (\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \left(\frac{\varepsilon \cdot \left({\left(\left(\varepsilon \cdot \frac{-2}{3}\right) \cdot \varepsilon\right)}^{3} - {2}^{3}\right)}{\color{blue}{(2 \cdot \left(\varepsilon \cdot \left(\varepsilon \cdot \frac{-2}{3}\right)\right) + \left((\left(\varepsilon \cdot \left(\varepsilon \cdot \frac{-2}{3}\right)\right) \cdot \left(\varepsilon \cdot \left(\varepsilon \cdot \frac{-2}{3}\right)\right) + 4)_*\right))_*}}\right))_*\]
  8. Final simplification0.2

    \[\leadsto (\left({\varepsilon}^{5}\right) \cdot \frac{-2}{5} + \left(\frac{\left({\left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right)}^{3} - 8\right) \cdot \varepsilon}{(2 \cdot \left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) + \left((\left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) \cdot \left(\left(\frac{-2}{3} \cdot \varepsilon\right) \cdot \varepsilon\right) + 4)_*\right))_*}\right))_*\]

Reproduce

herbie shell --seed 2019100 +o rules:numerics
(FPCore (eps)
  :name "logq (problem 3.4.3)"

  :herbie-target
  (* -2 (+ (+ eps (/ (pow eps 3) 3)) (/ (pow eps 5) 5)))

  (log (/ (- 1 eps) (+ 1 eps))))