Average Error: 58.6 → 0.2
Time: 28.2s
Precision: 64
Internal Precision: 1344
\[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)\]
\[(\left(\varepsilon \cdot -2\right) \cdot \left(\frac{1}{5} \cdot {\varepsilon}^{4}\right) + \left((\left({\varepsilon}^{3}\right) \cdot \left(-2 \cdot \frac{1}{3}\right) + \left(\varepsilon \cdot -2\right))_*\right))_*\]

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

    \[\leadsto \color{blue}{(\left((\left(\varepsilon \cdot \varepsilon\right) \cdot \frac{2}{3} + 2)_*\right) \cdot \left(-\varepsilon\right) + \left(\left(-\frac{2}{5}\right) \cdot {\varepsilon}^{5}\right))_*}\]
  4. Using strategy rm
  5. Applied add-exp-log34.7

    \[\leadsto \color{blue}{e^{\log \left((\left((\left(\varepsilon \cdot \varepsilon\right) \cdot \frac{2}{3} + 2)_*\right) \cdot \left(-\varepsilon\right) + \left(\left(-\frac{2}{5}\right) \cdot {\varepsilon}^{5}\right))_*\right)}}\]
  6. Taylor expanded around 0 62.9

    \[\leadsto \color{blue}{\frac{1}{3} \cdot \left(e^{\log -2 + \log \varepsilon} \cdot {\varepsilon}^{2}\right) + \left(e^{\log -2 + \log \varepsilon} + \frac{1}{5} \cdot \left(e^{\log -2 + \log \varepsilon} \cdot {\varepsilon}^{4}\right)\right)}\]
  7. Simplified0.2

    \[\leadsto \color{blue}{(\left(\varepsilon \cdot -2\right) \cdot \left(\frac{1}{5} \cdot {\varepsilon}^{4}\right) + \left((\left({\varepsilon}^{3}\right) \cdot \left(\frac{1}{3} \cdot -2\right) + \left(\varepsilon \cdot -2\right))_*\right))_*}\]
  8. Final simplification0.2

    \[\leadsto (\left(\varepsilon \cdot -2\right) \cdot \left(\frac{1}{5} \cdot {\varepsilon}^{4}\right) + \left((\left({\varepsilon}^{3}\right) \cdot \left(-2 \cdot \frac{1}{3}\right) + \left(\varepsilon \cdot -2\right))_*\right))_*\]

Runtime

Time bar (total: 28.2s)Debug logProfile

herbie shell --seed 2018221 +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))))