Average Error: 59.5 → 0.1
Time: 22.2s
Precision: 64
Internal Precision: 1408
\[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)\]
↓
\[-\left(\frac{2}{5} \cdot {\varepsilon}^{5} + \left(2 \cdot \varepsilon + \frac{2}{3} \cdot {\varepsilon}^{3}\right)\right)\]

Error

Bits error versus eps

Target

Original59.5
Target0.1
Herbie0.1
\[-2 \cdot \left(\left(\varepsilon + \frac{{\varepsilon}^{3}}{3}\right) + \frac{{\varepsilon}^{5}}{5}\right)\]

Derivation

  1. Initial program 59.5

    \[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)\]

  2. Taylor expanded around 0 0.1

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

Runtime

Time bar (total: 22.2s)Debug log

herbie shell --seed '#(151349756 408087815 228312487 2538703040 1980610373 1250971417)' 
(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))))