Average Error: 30.7 → 17.3
Time: 3.6s
Precision: 64
\[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
\[\begin{array}{l} \mathbf{if}\;re \le -3.5169395164413523 \cdot 10^{+139}:\\ \;\;\;\;\log \left(-re\right)\\ \mathbf{elif}\;re \le 3.0686185096665187 \cdot 10^{+60}:\\ \;\;\;\;\log \left(\sqrt{im \cdot im + re \cdot re}\right)\\ \mathbf{else}:\\ \;\;\;\;\log re\\ \end{array}\]
double f(double re, double im) {
        double r1675684 = re;
        double r1675685 = r1675684 * r1675684;
        double r1675686 = im;
        double r1675687 = r1675686 * r1675686;
        double r1675688 = r1675685 + r1675687;
        double r1675689 = sqrt(r1675688);
        double r1675690 = log(r1675689);
        return r1675690;
}

double f(double re, double im) {
        double r1675691 = re;
        double r1675692 = -3.5169395164413523e+139;
        bool r1675693 = r1675691 <= r1675692;
        double r1675694 = -r1675691;
        double r1675695 = log(r1675694);
        double r1675696 = 3.0686185096665187e+60;
        bool r1675697 = r1675691 <= r1675696;
        double r1675698 = im;
        double r1675699 = r1675698 * r1675698;
        double r1675700 = r1675691 * r1675691;
        double r1675701 = r1675699 + r1675700;
        double r1675702 = sqrt(r1675701);
        double r1675703 = log(r1675702);
        double r1675704 = log(r1675691);
        double r1675705 = r1675697 ? r1675703 : r1675704;
        double r1675706 = r1675693 ? r1675695 : r1675705;
        return r1675706;
}

\log \left(\sqrt{re \cdot re + im \cdot im}\right)
\begin{array}{l}
\mathbf{if}\;re \le -3.5169395164413523 \cdot 10^{+139}:\\
\;\;\;\;\log \left(-re\right)\\

\mathbf{elif}\;re \le 3.0686185096665187 \cdot 10^{+60}:\\
\;\;\;\;\log \left(\sqrt{im \cdot im + re \cdot re}\right)\\

\mathbf{else}:\\
\;\;\;\;\log re\\

\end{array}

Error

Bits error versus re

Bits error versus im

Derivation

  1. Split input into 3 regimes
  2. if re < -3.5169395164413523e+139

    1. Initial program 58.4

      \[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
    2. Taylor expanded around -inf 7.4

      \[\leadsto \log \color{blue}{\left(-1 \cdot re\right)}\]
    3. Simplified7.4

      \[\leadsto \log \color{blue}{\left(-re\right)}\]

    if -3.5169395164413523e+139 < re < 3.0686185096665187e+60

    1. Initial program 21.2

      \[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]

    if 3.0686185096665187e+60 < re

    1. Initial program 44.8

      \[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
    2. Taylor expanded around inf 10.8

      \[\leadsto \log \color{blue}{re}\]
  3. Recombined 3 regimes into one program.
  4. Final simplification17.3

    \[\leadsto \begin{array}{l} \mathbf{if}\;re \le -3.5169395164413523 \cdot 10^{+139}:\\ \;\;\;\;\log \left(-re\right)\\ \mathbf{elif}\;re \le 3.0686185096665187 \cdot 10^{+60}:\\ \;\;\;\;\log \left(\sqrt{im \cdot im + re \cdot re}\right)\\ \mathbf{else}:\\ \;\;\;\;\log re\\ \end{array}\]

Reproduce

herbie shell --seed 2019102 
(FPCore (re im)
  :name "math.log/1 on complex, real part"
  (log (sqrt (+ (* re re) (* im im)))))