Average Error: 58.6 → 0.2
Time: 32.8s
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 r12672980 = 1.0;
        double r12672981 = 2.0;
        double r12672982 = r12672980 / r12672981;
        double r12672983 = x;
        double r12672984 = r12672980 + r12672983;
        double r12672985 = r12672980 - r12672983;
        double r12672986 = r12672984 / r12672985;
        double r12672987 = log(r12672986);
        double r12672988 = r12672982 * r12672987;
        return r12672988;
}

double f(double x) {
        double r12672989 = 0.4;
        double r12672990 = x;
        double r12672991 = 5.0;
        double r12672992 = pow(r12672990, r12672991);
        double r12672993 = 2.0;
        double r12672994 = r12672993 * r12672990;
        double r12672995 = 0.6666666666666666;
        double r12672996 = r12672990 * r12672990;
        double r12672997 = r12672995 * r12672996;
        double r12672998 = r12672997 * r12672990;
        double r12672999 = r12672994 + r12672998;
        double r12673000 = fma(r12672989, r12672992, r12672999);
        double r12673001 = 0.5;
        double r12673002 = r12673000 * r12673001;
        return r12673002;
}

\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 2019102 +o rules:numerics
(FPCore (x)
  :name "Hyperbolic arc-(co)tangent"
  (* (/ 1 2) (log (/ (+ 1 x) (- 1 x)))))