Average Error: 58.6 → 0.2
Time: 26.7s
Precision: 64
\[\frac{1}{2} \cdot \log \left(\frac{1 + x}{1 - x}\right)\]
\[(\frac{2}{5} \cdot \left({x}^{5}\right) + \left(2 \cdot x + \left(\frac{2}{3} \cdot \left(x \cdot x\right)\right) \cdot x\right))_* \cdot \frac{1}{2}\]
double f(double x) {
        double r13566077 = 1.0;
        double r13566078 = 2.0;
        double r13566079 = r13566077 / r13566078;
        double r13566080 = x;
        double r13566081 = r13566077 + r13566080;
        double r13566082 = r13566077 - r13566080;
        double r13566083 = r13566081 / r13566082;
        double r13566084 = log(r13566083);
        double r13566085 = r13566079 * r13566084;
        return r13566085;
}

double f(double x) {
        double r13566086 = 0.4;
        double r13566087 = x;
        double r13566088 = 5.0;
        double r13566089 = pow(r13566087, r13566088);
        double r13566090 = 2.0;
        double r13566091 = r13566090 * r13566087;
        double r13566092 = 0.6666666666666666;
        double r13566093 = r13566087 * r13566087;
        double r13566094 = r13566092 * r13566093;
        double r13566095 = r13566094 * r13566087;
        double r13566096 = r13566091 + r13566095;
        double r13566097 = fma(r13566086, r13566089, r13566096);
        double r13566098 = 0.5;
        double r13566099 = r13566097 * r13566098;
        return r13566099;
}

\frac{1}{2} \cdot \log \left(\frac{1 + x}{1 - x}\right)
(\frac{2}{5} \cdot \left({x}^{5}\right) + \left(2 \cdot x + \left(\frac{2}{3} \cdot \left(x \cdot x\right)\right) \cdot x\right))_* \cdot \frac{1}{2}

Error

Bits error versus x

Derivation

  1. Initial program 58.6

    \[\frac{1}{2} \cdot \log \left(\frac{1 + x}{1 - x}\right)\]
  2. Simplified58.6

    \[\leadsto \color{blue}{\log \left(\frac{x + 1}{1 - x}\right) \cdot \frac{1}{2}}\]
  3. Taylor expanded around 0 0.2

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

    \[\leadsto \color{blue}{(\frac{2}{5} \cdot \left({x}^{5}\right) + \left(x \cdot (\frac{2}{3} \cdot \left(x \cdot x\right) + 2)_*\right))_*} \cdot \frac{1}{2}\]
  5. Using strategy rm
  6. Applied fma-udef0.2

    \[\leadsto (\frac{2}{5} \cdot \left({x}^{5}\right) + \left(x \cdot \color{blue}{\left(\frac{2}{3} \cdot \left(x \cdot x\right) + 2\right)}\right))_* \cdot \frac{1}{2}\]
  7. Applied distribute-lft-in0.2

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

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

Reproduce

herbie shell --seed 2019101 +o rules:numerics
(FPCore (x)
  :name "Hyperbolic arc-(co)tangent"
  (* (/ 1 2) (log (/ (+ 1 x) (- 1 x)))))