Average Error: 52.5 → 0.2
Time: 6.1s
Precision: 64
\[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
\[\begin{array}{l} \mathbf{if}\;x \le -1.0301407998346479:\\ \;\;\;\;\log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right) + \log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right)\\ \mathbf{elif}\;x \le 0.89162235529366485:\\ \;\;\;\;\left(\log \left(\sqrt{1}\right) + \frac{x}{\sqrt{1}}\right) - \frac{1}{6} \cdot \frac{{x}^{3}}{{\left(\sqrt{1}\right)}^{3}}\\ \mathbf{else}:\\ \;\;\;\;\log \left(x + \left(\left(x + \frac{0.5}{x}\right) - \frac{0.125}{{x}^{3}}\right)\right)\\ \end{array}\]
\log \left(x + \sqrt{x \cdot x + 1}\right)
\begin{array}{l}
\mathbf{if}\;x \le -1.0301407998346479:\\
\;\;\;\;\log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right) + \log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right)\\

\mathbf{elif}\;x \le 0.89162235529366485:\\
\;\;\;\;\left(\log \left(\sqrt{1}\right) + \frac{x}{\sqrt{1}}\right) - \frac{1}{6} \cdot \frac{{x}^{3}}{{\left(\sqrt{1}\right)}^{3}}\\

\mathbf{else}:\\
\;\;\;\;\log \left(x + \left(\left(x + \frac{0.5}{x}\right) - \frac{0.125}{{x}^{3}}\right)\right)\\

\end{array}
double f(double x) {
        double r217597 = x;
        double r217598 = r217597 * r217597;
        double r217599 = 1.0;
        double r217600 = r217598 + r217599;
        double r217601 = sqrt(r217600);
        double r217602 = r217597 + r217601;
        double r217603 = log(r217602);
        return r217603;
}

double f(double x) {
        double r217604 = x;
        double r217605 = -1.030140799834648;
        bool r217606 = r217604 <= r217605;
        double r217607 = 0.125;
        double r217608 = 3.0;
        double r217609 = pow(r217604, r217608);
        double r217610 = r217607 / r217609;
        double r217611 = 0.5;
        double r217612 = r217611 / r217604;
        double r217613 = 0.0625;
        double r217614 = -r217613;
        double r217615 = 5.0;
        double r217616 = pow(r217604, r217615);
        double r217617 = r217614 / r217616;
        double r217618 = r217612 - r217617;
        double r217619 = r217610 - r217618;
        double r217620 = sqrt(r217619);
        double r217621 = log(r217620);
        double r217622 = r217621 + r217621;
        double r217623 = 0.8916223552936648;
        bool r217624 = r217604 <= r217623;
        double r217625 = 1.0;
        double r217626 = sqrt(r217625);
        double r217627 = log(r217626);
        double r217628 = r217604 / r217626;
        double r217629 = r217627 + r217628;
        double r217630 = 0.16666666666666666;
        double r217631 = pow(r217626, r217608);
        double r217632 = r217609 / r217631;
        double r217633 = r217630 * r217632;
        double r217634 = r217629 - r217633;
        double r217635 = r217604 + r217612;
        double r217636 = r217635 - r217610;
        double r217637 = r217604 + r217636;
        double r217638 = log(r217637);
        double r217639 = r217624 ? r217634 : r217638;
        double r217640 = r217606 ? r217622 : r217639;
        return r217640;
}

Error

Bits error versus x

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original52.5
Target44.7
Herbie0.2
\[\begin{array}{l} \mathbf{if}\;x \lt 0.0:\\ \;\;\;\;\log \left(\frac{-1}{x - \sqrt{x \cdot x + 1}}\right)\\ \mathbf{else}:\\ \;\;\;\;\log \left(x + \sqrt{x \cdot x + 1}\right)\\ \end{array}\]

Derivation

  1. Split input into 3 regimes
  2. if x < -1.030140799834648

    1. Initial program 62.8

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

      \[\leadsto \log \color{blue}{\left(0.125 \cdot \frac{1}{{x}^{3}} - \left(0.5 \cdot \frac{1}{x} + 0.0625 \cdot \frac{1}{{x}^{5}}\right)\right)}\]
    3. Simplified0.2

      \[\leadsto \log \color{blue}{\left(\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)\right)}\]
    4. Using strategy rm
    5. Applied add-sqr-sqrt0.2

      \[\leadsto \log \color{blue}{\left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)} \cdot \sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right)}\]
    6. Applied log-prod0.2

      \[\leadsto \color{blue}{\log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right) + \log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right)}\]

    if -1.030140799834648 < x < 0.8916223552936648

    1. Initial program 58.7

      \[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
    2. Taylor expanded around 0 0.3

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

    if 0.8916223552936648 < x

    1. Initial program 30.6

      \[\log \left(x + \sqrt{x \cdot x + 1}\right)\]
    2. Taylor expanded around inf 0.2

      \[\leadsto \log \left(x + \color{blue}{\left(\left(x + 0.5 \cdot \frac{1}{x}\right) - 0.125 \cdot \frac{1}{{x}^{3}}\right)}\right)\]
    3. Simplified0.2

      \[\leadsto \log \left(x + \color{blue}{\left(\left(x + \frac{0.5}{x}\right) - \frac{0.125}{{x}^{3}}\right)}\right)\]
  3. Recombined 3 regimes into one program.
  4. Final simplification0.2

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \le -1.0301407998346479:\\ \;\;\;\;\log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right) + \log \left(\sqrt{\frac{0.125}{{x}^{3}} - \left(\frac{0.5}{x} - \frac{-0.0625}{{x}^{5}}\right)}\right)\\ \mathbf{elif}\;x \le 0.89162235529366485:\\ \;\;\;\;\left(\log \left(\sqrt{1}\right) + \frac{x}{\sqrt{1}}\right) - \frac{1}{6} \cdot \frac{{x}^{3}}{{\left(\sqrt{1}\right)}^{3}}\\ \mathbf{else}:\\ \;\;\;\;\log \left(x + \left(\left(x + \frac{0.5}{x}\right) - \frac{0.125}{{x}^{3}}\right)\right)\\ \end{array}\]

Reproduce

herbie shell --seed 2020064 
(FPCore (x)
  :name "Hyperbolic arcsine"
  :precision binary64

  :herbie-target
  (if (< x 0.0) (log (/ -1 (- x (sqrt (+ (* x x) 1))))) (log (+ x (sqrt (+ (* x x) 1)))))

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