Average Error: 33.6 → 9.6
Time: 23.7s
Precision: 64
\[\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}\]
\[\begin{array}{l} \mathbf{if}\;b \le -9.768773924260542 \cdot 10^{+151}:\\ \;\;\;\;\frac{\left(\frac{c}{b} - \frac{b}{a}\right) \cdot 2}{2}\\ \mathbf{elif}\;b \le 5.9878793504095505 \cdot 10^{-84}:\\ \;\;\;\;\frac{\frac{\sqrt{\mathsf{fma}\left(b, b, -4 \cdot \left(a \cdot c\right)\right)} - b}{a}}{2}\\ \mathbf{else}:\\ \;\;\;\;\frac{\frac{c}{b} \cdot -2}{2}\\ \end{array}\]
\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}
\begin{array}{l}
\mathbf{if}\;b \le -9.768773924260542 \cdot 10^{+151}:\\
\;\;\;\;\frac{\left(\frac{c}{b} - \frac{b}{a}\right) \cdot 2}{2}\\

\mathbf{elif}\;b \le 5.9878793504095505 \cdot 10^{-84}:\\
\;\;\;\;\frac{\frac{\sqrt{\mathsf{fma}\left(b, b, -4 \cdot \left(a \cdot c\right)\right)} - b}{a}}{2}\\

\mathbf{else}:\\
\;\;\;\;\frac{\frac{c}{b} \cdot -2}{2}\\

\end{array}
double f(double a, double b, double c) {
        double r2184092 = b;
        double r2184093 = -r2184092;
        double r2184094 = r2184092 * r2184092;
        double r2184095 = 4.0;
        double r2184096 = a;
        double r2184097 = c;
        double r2184098 = r2184096 * r2184097;
        double r2184099 = r2184095 * r2184098;
        double r2184100 = r2184094 - r2184099;
        double r2184101 = sqrt(r2184100);
        double r2184102 = r2184093 + r2184101;
        double r2184103 = 2.0;
        double r2184104 = r2184103 * r2184096;
        double r2184105 = r2184102 / r2184104;
        return r2184105;
}

double f(double a, double b, double c) {
        double r2184106 = b;
        double r2184107 = -9.768773924260542e+151;
        bool r2184108 = r2184106 <= r2184107;
        double r2184109 = c;
        double r2184110 = r2184109 / r2184106;
        double r2184111 = a;
        double r2184112 = r2184106 / r2184111;
        double r2184113 = r2184110 - r2184112;
        double r2184114 = 2.0;
        double r2184115 = r2184113 * r2184114;
        double r2184116 = r2184115 / r2184114;
        double r2184117 = 5.9878793504095505e-84;
        bool r2184118 = r2184106 <= r2184117;
        double r2184119 = -4.0;
        double r2184120 = r2184111 * r2184109;
        double r2184121 = r2184119 * r2184120;
        double r2184122 = fma(r2184106, r2184106, r2184121);
        double r2184123 = sqrt(r2184122);
        double r2184124 = r2184123 - r2184106;
        double r2184125 = r2184124 / r2184111;
        double r2184126 = r2184125 / r2184114;
        double r2184127 = -2.0;
        double r2184128 = r2184110 * r2184127;
        double r2184129 = r2184128 / r2184114;
        double r2184130 = r2184118 ? r2184126 : r2184129;
        double r2184131 = r2184108 ? r2184116 : r2184130;
        return r2184131;
}

Error

Bits error versus a

Bits error versus b

Bits error versus c

Target

Original33.6
Target20.4
Herbie9.6
\[\begin{array}{l} \mathbf{if}\;b \lt 0:\\ \;\;\;\;\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}\\ \mathbf{else}:\\ \;\;\;\;\frac{c}{a \cdot \frac{\left(-b\right) - \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}}\\ \end{array}\]

Derivation

  1. Split input into 3 regimes
  2. if b < -9.768773924260542e+151

    1. Initial program 60.2

      \[\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}\]
    2. Simplified60.2

      \[\leadsto \color{blue}{\frac{\frac{\sqrt{\mathsf{fma}\left(a \cdot c, -4, b \cdot b\right)} - b}{a}}{2}}\]
    3. Taylor expanded around inf 60.2

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{{b}^{2} - 4 \cdot \left(a \cdot c\right)}} - b}{a}}{2}\]
    4. Simplified60.2

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{\mathsf{fma}\left(b, b, \left(a \cdot c\right) \cdot -4\right)}} - b}{a}}{2}\]
    5. Taylor expanded around -inf 1.7

      \[\leadsto \frac{\color{blue}{2 \cdot \frac{c}{b} - 2 \cdot \frac{b}{a}}}{2}\]
    6. Simplified1.7

      \[\leadsto \frac{\color{blue}{2 \cdot \left(\frac{c}{b} - \frac{b}{a}\right)}}{2}\]

    if -9.768773924260542e+151 < b < 5.9878793504095505e-84

    1. Initial program 11.8

      \[\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}\]
    2. Simplified11.8

      \[\leadsto \color{blue}{\frac{\frac{\sqrt{\mathsf{fma}\left(a \cdot c, -4, b \cdot b\right)} - b}{a}}{2}}\]
    3. Taylor expanded around inf 11.8

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{{b}^{2} - 4 \cdot \left(a \cdot c\right)}} - b}{a}}{2}\]
    4. Simplified11.8

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{\mathsf{fma}\left(b, b, \left(a \cdot c\right) \cdot -4\right)}} - b}{a}}{2}\]

    if 5.9878793504095505e-84 < b

    1. Initial program 52.2

      \[\frac{\left(-b\right) + \sqrt{b \cdot b - 4 \cdot \left(a \cdot c\right)}}{2 \cdot a}\]
    2. Simplified52.2

      \[\leadsto \color{blue}{\frac{\frac{\sqrt{\mathsf{fma}\left(a \cdot c, -4, b \cdot b\right)} - b}{a}}{2}}\]
    3. Taylor expanded around inf 52.2

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{{b}^{2} - 4 \cdot \left(a \cdot c\right)}} - b}{a}}{2}\]
    4. Simplified52.2

      \[\leadsto \frac{\frac{\sqrt{\color{blue}{\mathsf{fma}\left(b, b, \left(a \cdot c\right) \cdot -4\right)}} - b}{a}}{2}\]
    5. Taylor expanded around inf 9.3

      \[\leadsto \frac{\color{blue}{-2 \cdot \frac{c}{b}}}{2}\]
  3. Recombined 3 regimes into one program.
  4. Final simplification9.6

    \[\leadsto \begin{array}{l} \mathbf{if}\;b \le -9.768773924260542 \cdot 10^{+151}:\\ \;\;\;\;\frac{\left(\frac{c}{b} - \frac{b}{a}\right) \cdot 2}{2}\\ \mathbf{elif}\;b \le 5.9878793504095505 \cdot 10^{-84}:\\ \;\;\;\;\frac{\frac{\sqrt{\mathsf{fma}\left(b, b, -4 \cdot \left(a \cdot c\right)\right)} - b}{a}}{2}\\ \mathbf{else}:\\ \;\;\;\;\frac{\frac{c}{b} \cdot -2}{2}\\ \end{array}\]

Reproduce

herbie shell --seed 2019144 +o rules:numerics
(FPCore (a b c)
  :name "quadp (p42, positive)"

  :herbie-target
  (if (< b 0) (/ (+ (- b) (sqrt (- (* b b) (* 4 (* a c))))) (* 2 a)) (/ c (* a (/ (- (- b) (sqrt (- (* b b) (* 4 (* a c))))) (* 2 a)))))

  (/ (+ (- b) (sqrt (- (* b b) (* 4 (* a c))))) (* 2 a)))