Diagrams.Solve.Polynomial:cubForm from diagrams-solve-0.1, I

Average Error: 7.9 → 0.9

Time: 5.2s

Precision: binary64

Math

\[\frac{x \cdot y - \left(z \cdot 9\right) \cdot t}{a \cdot 2}\]

↓

\[\begin{array}{l} \mathbf{if}\;x \cdot y - \left(z \cdot 9\right) \cdot t \le -6.6434041933501398 \cdot 10^{183} \lor \neg \left(x \cdot y - \left(z \cdot 9\right) \cdot t \le 8.10187241503442859 \cdot 10^{265}\right):\\ \;\;\;\;0.5 \cdot \left(y \cdot \frac{x}{a}\right) - z \cdot \left(4.5 \cdot \frac{t}{a}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{x \cdot y - \left(z \cdot 9\right) \cdot t}{a \cdot 2}\\ \end{array}\]

C

double code(double x, double y, double z, double t, double a) {
	return (((double) (((double) (x * y)) - ((double) (((double) (z * 9.0)) * t)))) / ((double) (a * 2.0)));
}

↓

double code(double x, double y, double z, double t, double a) {
	double VAR;
	if (((((double) (((double) (x * y)) - ((double) (((double) (z * 9.0)) * t)))) <= -6.64340419335014e+183) || !(((double) (((double) (x * y)) - ((double) (((double) (z * 9.0)) * t)))) <= 8.101872415034429e+265))) {
		VAR = ((double) (((double) (0.5 * ((double) (y * (x / a))))) - ((double) (z * ((double) (4.5 * (t / a)))))));
	} else {
		VAR = (((double) (((double) (x * y)) - ((double) (((double) (z * 9.0)) * t)))) / ((double) (a * 2.0)));
	}
	return VAR;
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Bits error versus t

Bits error versus a

Target

Original	7.9
Target	5.6
Herbie	0.9

\[\begin{array}{l} \mathbf{if}\;a \lt -2.090464557976709 \cdot 10^{86}:\\ \;\;\;\;0.5 \cdot \frac{y \cdot x}{a} - 4.5 \cdot \frac{t}{\frac{a}{z}}\\ \mathbf{elif}\;a \lt 2.14403070783397609 \cdot 10^{99}:\\ \;\;\;\;\frac{x \cdot y - z \cdot \left(9 \cdot t\right)}{a \cdot 2}\\ \mathbf{else}:\\ \;\;\;\;\frac{y}{a} \cdot \left(x \cdot 0.5\right) - \frac{t}{a} \cdot \left(z \cdot 4.5\right)\\ \end{array}\]

Derivation

1. Split input into 2 regimes

2. if (- (* x y) (* (* z 9.0) t)) < -6.6434041933501398e183 or 8.10187241503442859e265 < (- (* x y) (* (* z 9.0) t))

   1. Initial program 32.9

      \[\frac{x \cdot y - \left(z \cdot 9\right) \cdot t}{a \cdot 2}\]

   2. Taylor expanded around 0 32.7

      \[\leadsto \color{blue}{0.5 \cdot \frac{x \cdot y}{a} - 4.5 \cdot \frac{t \cdot z}{a}}\]

   3. Simplified 1.2

      \[\leadsto \color{blue}{0.5 \cdot \left(y \cdot \frac{x}{a}\right) - 4.5 \cdot \left(z \cdot \frac{t}{a}\right)}\]

   4. Taylor expanded around 0 18.6

      \[\leadsto 0.5 \cdot \left(y \cdot \frac{x}{a}\right) - \color{blue}{4.5 \cdot \frac{t \cdot z}{a}}\]

   5. Simplified 1.2

      \[\leadsto 0.5 \cdot \left(y \cdot \frac{x}{a}\right) - \color{blue}{z \cdot \left(4.5 \cdot \frac{t}{a}\right)}\]

   if -6.6434041933501398e183 < (- (* x y) (* (* z 9.0) t)) < 8.10187241503442859e265

   1. Initial program 0.8

      \[\frac{x \cdot y - \left(z \cdot 9\right) \cdot t}{a \cdot 2}\]
3. Recombined 2 regimes into one program.

4. Final simplification 0.9

   \[\leadsto \begin{array}{l} \mathbf{if}\;x \cdot y - \left(z \cdot 9\right) \cdot t \le -6.6434041933501398 \cdot 10^{183} \lor \neg \left(x \cdot y - \left(z \cdot 9\right) \cdot t \le 8.10187241503442859 \cdot 10^{265}\right):\\ \;\;\;\;0.5 \cdot \left(y \cdot \frac{x}{a}\right) - z \cdot \left(4.5 \cdot \frac{t}{a}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{x \cdot y - \left(z \cdot 9\right) \cdot t}{a \cdot 2}\\ \end{array}\]

Reproduce

herbie shell --seed 2020182 
(FPCore (x y z t a)
  :name "Diagrams.Solve.Polynomial:cubForm  from diagrams-solve-0.1, I"
  :precision binary64

  :herbie-target
  (if (< a -2.090464557976709e+86) (- (* 0.5 (/ (* y x) a)) (* 4.5 (/ t (/ a z)))) (if (< a 2.144030707833976e+99) (/ (- (* x y) (* z (* 9.0 t))) (* a 2.0)) (- (* (/ y a) (* x 0.5)) (* (/ t a) (* z 4.5)))))

  (/ (- (* x y) (* (* z 9.0) t)) (* a 2.0)))