Cubic critical, wide range

Average Error: 52.6 → 6.1

Time: 6.0s

Precision: 64

• Falling back on racket egraph because egg-herbie package not installed

\[4.93038 \cdot 10^{-32} \lt a \lt 2.02824 \cdot 10^{31} \land 4.93038 \cdot 10^{-32} \lt b \lt 2.02824 \cdot 10^{31} \land 4.93038 \cdot 10^{-32} \lt c \lt 2.02824 \cdot 10^{31}\]

Math

\[\frac{\left(-b\right) + \sqrt{b \cdot b - \left(3 \cdot a\right) \cdot c}}{3 \cdot a}\]

↓

\[-0.5 \cdot \frac{c}{b}\]

C

double f(double a, double b, double c) {
        double r72115 = b;
        double r72116 = -r72115;
        double r72117 = r72115 * r72115;
        double r72118 = 3.0;
        double r72119 = a;
        double r72120 = r72118 * r72119;
        double r72121 = c;
        double r72122 = r72120 * r72121;
        double r72123 = r72117 - r72122;
        double r72124 = sqrt(r72123);
        double r72125 = r72116 + r72124;
        double r72126 = r72125 / r72120;
        return r72126;
}

↓

double f(double __attribute__((unused)) a, double b, double c) {
        double r72127 = -0.5;
        double r72128 = c;
        double r72129 = b;
        double r72130 = r72128 / r72129;
        double r72131 = r72127 * r72130;
        return r72131;
}

Error

Bits error versus a

Bits error versus b

Bits error versus c

Derivation

1. Initial program 52.6

   \[\frac{\left(-b\right) + \sqrt{b \cdot b - \left(3 \cdot a\right) \cdot c}}{3 \cdot a}\]

2. Taylor expanded around inf 6.1

   \[\leadsto \color{blue}{-0.5 \cdot \frac{c}{b}}\]

3. Final simplification 6.1

   \[\leadsto -0.5 \cdot \frac{c}{b}\]

Reproduce

herbie shell --seed 2020047 +o rules:numerics
(FPCore (a b c)
  :name "Cubic critical, wide range"
  :precision binary64
  :pre (and (< 4.9303800000000003e-32 a 2.02824e+31) (< 4.9303800000000003e-32 b 2.02824e+31) (< 4.9303800000000003e-32 c 2.02824e+31))
  (/ (+ (- b) (sqrt (- (* b b) (* (* 3 a) c)))) (* 3 a)))