Average Error: 30.2 → 17.1
Time: 3.1s
Precision: 64
\[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
\[\begin{array}{l} \mathbf{if}\;re \le -1.9839400233753306 \cdot 10^{+87}:\\ \;\;\;\;\log \left(-re\right)\\ \mathbf{elif}\;re \le 7057901.046632865:\\ \;\;\;\;\log \left(\sqrt{im \cdot im + re \cdot re}\right)\\ \mathbf{else}:\\ \;\;\;\;\log re\\ \end{array}\]
double f(double re, double im) {
        double r1101657 = re;
        double r1101658 = r1101657 * r1101657;
        double r1101659 = im;
        double r1101660 = r1101659 * r1101659;
        double r1101661 = r1101658 + r1101660;
        double r1101662 = sqrt(r1101661);
        double r1101663 = log(r1101662);
        return r1101663;
}

double f(double re, double im) {
        double r1101664 = re;
        double r1101665 = -1.9839400233753306e+87;
        bool r1101666 = r1101664 <= r1101665;
        double r1101667 = -r1101664;
        double r1101668 = log(r1101667);
        double r1101669 = 7057901.046632865;
        bool r1101670 = r1101664 <= r1101669;
        double r1101671 = im;
        double r1101672 = r1101671 * r1101671;
        double r1101673 = r1101664 * r1101664;
        double r1101674 = r1101672 + r1101673;
        double r1101675 = sqrt(r1101674);
        double r1101676 = log(r1101675);
        double r1101677 = log(r1101664);
        double r1101678 = r1101670 ? r1101676 : r1101677;
        double r1101679 = r1101666 ? r1101668 : r1101678;
        return r1101679;
}

\log \left(\sqrt{re \cdot re + im \cdot im}\right)
\begin{array}{l}
\mathbf{if}\;re \le -1.9839400233753306 \cdot 10^{+87}:\\
\;\;\;\;\log \left(-re\right)\\

\mathbf{elif}\;re \le 7057901.046632865:\\
\;\;\;\;\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 < -1.9839400233753306e+87

    1. Initial program 47.8

      \[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
    2. Taylor expanded around -inf 8.8

      \[\leadsto \log \color{blue}{\left(-1 \cdot re\right)}\]
    3. Simplified8.8

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

    if -1.9839400233753306e+87 < re < 7057901.046632865

    1. Initial program 21.4

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

    if 7057901.046632865 < re

    1. Initial program 38.4

      \[\log \left(\sqrt{re \cdot re + im \cdot im}\right)\]
    2. Taylor expanded around inf 12.7

      \[\leadsto \log \color{blue}{re}\]
  3. Recombined 3 regimes into one program.
  4. Final simplification17.1

    \[\leadsto \begin{array}{l} \mathbf{if}\;re \le -1.9839400233753306 \cdot 10^{+87}:\\ \;\;\;\;\log \left(-re\right)\\ \mathbf{elif}\;re \le 7057901.046632865:\\ \;\;\;\;\log \left(\sqrt{im \cdot im + re \cdot re}\right)\\ \mathbf{else}:\\ \;\;\;\;\log re\\ \end{array}\]

Reproduce

herbie shell --seed 2019101 
(FPCore (re im)
  :name "math.log/1 on complex, real part"
  (log (sqrt (+ (* re re) (* im im)))))