Average Error: 52.6 → 0.1
Time: 23.5s
Precision: 64
Internal Precision: 2368
\[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
\[\begin{array}{l} \mathbf{if}\;x \le -1.0712784506357302:\\ \;\;\;\;\log \left((\left((\left(\frac{\frac{1}{8}}{x}\right) \cdot \left(\frac{1}{x}\right) + \left(-\frac{1}{2}\right))_*\right) \cdot \left(\frac{1}{x}\right) + \left(\frac{-\frac{1}{16}}{{x}^{5}}\right))_*\right)\\ \mathbf{elif}\;x \le 0.008931035360035398:\\ \;\;\;\;\left({x}^{5} \cdot \frac{3}{40} + x\right) - {x}^{3} \cdot \frac{1}{6}\\ \mathbf{else}:\\ \;\;\;\;\log \left(\sqrt{\sqrt{1^2 + x^2}^*} \cdot \sqrt{\sqrt{1^2 + x^2}^*} + x\right)\\ \end{array}\]

Error

Bits error versus x

Target

Original52.6
Target44.9
Herbie0.1
\[\begin{array}{l} \mathbf{if}\;x \lt 0:\\ \;\;\;\;\log \left(\frac{-1}{x - \sqrt{x \cdot x + 1}}\right)\\ \mathbf{else}:\\ \;\;\;\;\log \left(x + \sqrt{x \cdot x + 1}\right)\\ \end{array}\]

Derivation

  1. Split input into 3 regimes
  2. if x < -1.0712784506357302

    1. Initial program 61.8

      \[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
    2. Initial simplification61.0

      \[\leadsto \log \left(x + \sqrt{1^2 + x^2}^*\right)\]
    3. Taylor expanded around -inf 0.2

      \[\leadsto \log \color{blue}{\left(\frac{1}{8} \cdot \frac{1}{{x}^{3}} - \left(\frac{1}{16} \cdot \frac{1}{{x}^{5}} + \frac{1}{2} \cdot \frac{1}{x}\right)\right)}\]
    4. Simplified0.2

      \[\leadsto \log \color{blue}{\left((\left((\left(\frac{\frac{1}{8}}{x}\right) \cdot \left(\frac{1}{x}\right) + \left(-\frac{1}{2}\right))_*\right) \cdot \left(\frac{1}{x}\right) + \left(\frac{-\frac{1}{16}}{{x}^{5}}\right))_*\right)}\]

    if -1.0712784506357302 < x < 0.008931035360035398

    1. Initial program 58.8

      \[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
    2. Initial simplification58.8

      \[\leadsto \log \left(x + \sqrt{1^2 + x^2}^*\right)\]
    3. Taylor expanded around 0 0.1

      \[\leadsto \color{blue}{\left(x + \frac{3}{40} \cdot {x}^{5}\right) - \frac{1}{6} \cdot {x}^{3}}\]

    if 0.008931035360035398 < x

    1. Initial program 31.3

      \[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
    2. Initial simplification0.0

      \[\leadsto \log \left(x + \sqrt{1^2 + x^2}^*\right)\]
    3. Using strategy rm
    4. Applied add-sqr-sqrt0.0

      \[\leadsto \log \left(x + \color{blue}{\sqrt{\sqrt{1^2 + x^2}^*} \cdot \sqrt{\sqrt{1^2 + x^2}^*}}\right)\]
  3. Recombined 3 regimes into one program.
  4. Final simplification0.1

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \le -1.0712784506357302:\\ \;\;\;\;\log \left((\left((\left(\frac{\frac{1}{8}}{x}\right) \cdot \left(\frac{1}{x}\right) + \left(-\frac{1}{2}\right))_*\right) \cdot \left(\frac{1}{x}\right) + \left(\frac{-\frac{1}{16}}{{x}^{5}}\right))_*\right)\\ \mathbf{elif}\;x \le 0.008931035360035398:\\ \;\;\;\;\left({x}^{5} \cdot \frac{3}{40} + x\right) - {x}^{3} \cdot \frac{1}{6}\\ \mathbf{else}:\\ \;\;\;\;\log \left(\sqrt{\sqrt{1^2 + x^2}^*} \cdot \sqrt{\sqrt{1^2 + x^2}^*} + x\right)\\ \end{array}\]

Runtime

Time bar (total: 23.5s)Debug logProfile

herbie shell --seed 2018217 +o rules:numerics
(FPCore (x)
  :name "Hyperbolic arcsine"

  :herbie-target
  (if (< x 0) (log (/ -1 (- x (sqrt (+ (* x x) 1))))) (log (+ x (sqrt (+ (* x x) 1)))))

  (log (+ x (sqrt (+ (* x x) 1)))))