Linear.Quaternion:$ctan from linear-1.19.1.3

Average Error: 7.4 → 0.5

Time: 5.0s

Precision: binary64

Math

\[\frac{\cosh x \cdot \frac{y}{x}}{z}\]

↓

\[\begin{array}{l} \mathbf{if}\;z \le -0.48421412719263424:\\ \;\;\;\;\cosh x \cdot \frac{1}{\frac{x \cdot z}{y}}\\ \mathbf{elif}\;z \le 9.40222425595707568 \cdot 10^{29}:\\ \;\;\;\;\frac{\cosh x \cdot \frac{y}{z}}{x}\\ \mathbf{else}:\\ \;\;\;\;\cosh x \cdot \left(y \cdot \frac{1}{x \cdot z}\right)\\ \end{array}\]

C

double code(double x, double y, double z) {
	return ((double) (((double) (((double) cosh(x)) * ((double) (y / x)))) / z));
}

↓

double code(double x, double y, double z) {
	double VAR;
	if ((z <= -0.48421412719263424)) {
		VAR = ((double) (((double) cosh(x)) * ((double) (1.0 / ((double) (((double) (x * z)) / y))))));
	} else {
		double VAR_1;
		if ((z <= 9.402224255957076e+29)) {
			VAR_1 = ((double) (((double) (((double) cosh(x)) * ((double) (y / z)))) / x));
		} else {
			VAR_1 = ((double) (((double) cosh(x)) * ((double) (y * ((double) (1.0 / ((double) (x * z))))))));
		}
		VAR = VAR_1;
	}
	return VAR;
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Target

Original	7.4
Target	0.5
Herbie	0.5

\[\begin{array}{l} \mathbf{if}\;y \lt -4.618902267687042 \cdot 10^{-52}:\\ \;\;\;\;\frac{\frac{y}{z}}{x} \cdot \cosh x\\ \mathbf{elif}\;y \lt 1.0385305359351529 \cdot 10^{-39}:\\ \;\;\;\;\frac{\frac{\cosh x \cdot y}{x}}{z}\\ \mathbf{else}:\\ \;\;\;\;\frac{\frac{y}{z}}{x} \cdot \cosh x\\ \end{array}\]

Derivation

1. Split input into 3 regimes

2. if z < -0.48421412719263424

   1. Initial program 10.7

      \[\frac{\cosh x \cdot \frac{y}{x}}{z}\]
   2. Using strategy rm

   3. Applied *-un-lft-identity 10.7

      \[\leadsto \frac{\cosh x \cdot \frac{y}{x}}{\color{blue}{1 \cdot z}}\]

   4. Applied times-frac 10.6

      \[\leadsto \color{blue}{\frac{\cosh x}{1} \cdot \frac{\frac{y}{x}}{z}}\]

   5. Simplified 10.6

      \[\leadsto \color{blue}{\cosh x} \cdot \frac{\frac{y}{x}}{z}\]

   6. Simplified 0.4

      \[\leadsto \cosh x \cdot \color{blue}{\frac{y}{x \cdot z}}\]
   7. Using strategy rm

   8. Applied clear-num 0.8

      \[\leadsto \cosh x \cdot \color{blue}{\frac{1}{\frac{x \cdot z}{y}}}\]

   if -0.48421412719263424 < z < 9.402224255957076e+29

   1. Initial program 0.4

      \[\frac{\cosh x \cdot \frac{y}{x}}{z}\]
   2. Using strategy rm

   3. Applied *-un-lft-identity 0.4

      \[\leadsto \frac{\cosh x \cdot \frac{y}{x}}{\color{blue}{1 \cdot z}}\]

   4. Applied times-frac 0.4

      \[\leadsto \color{blue}{\frac{\cosh x}{1} \cdot \frac{\frac{y}{x}}{z}}\]

   5. Simplified 0.4

      \[\leadsto \color{blue}{\cosh x} \cdot \frac{\frac{y}{x}}{z}\]

   6. Simplified 18.2

      \[\leadsto \cosh x \cdot \color{blue}{\frac{y}{x \cdot z}}\]
   7. Using strategy rm

   8. Applied *-un-lft-identity 18.2

      \[\leadsto \cosh x \cdot \frac{\color{blue}{1 \cdot y}}{x \cdot z}\]

   9. Applied times-frac 0.5

      \[\leadsto \cosh x \cdot \color{blue}{\left(\frac{1}{x} \cdot \frac{y}{z}\right)}\]

   10. Applied associate-*r* 0.5

       \[\leadsto \color{blue}{\left(\cosh x \cdot \frac{1}{x}\right) \cdot \frac{y}{z}}\]

   11. Simplified 0.5

       \[\leadsto \color{blue}{\frac{\cosh x}{x}} \cdot \frac{y}{z}\]
   12. Using strategy rm

   13. Applied associate-*l/ 0.3

       \[\leadsto \color{blue}{\frac{\cosh x \cdot \frac{y}{z}}{x}}\]

   if 9.402224255957076e+29 < z

   1. Initial program 13.0

      \[\frac{\cosh x \cdot \frac{y}{x}}{z}\]
   2. Using strategy rm

   3. Applied *-un-lft-identity 13.0

      \[\leadsto \frac{\cosh x \cdot \frac{y}{x}}{\color{blue}{1 \cdot z}}\]

   4. Applied times-frac 12.9

      \[\leadsto \color{blue}{\frac{\cosh x}{1} \cdot \frac{\frac{y}{x}}{z}}\]

   5. Simplified 12.9

      \[\leadsto \color{blue}{\cosh x} \cdot \frac{\frac{y}{x}}{z}\]

   6. Simplified 0.4

      \[\leadsto \cosh x \cdot \color{blue}{\frac{y}{x \cdot z}}\]
   7. Using strategy rm

   8. Applied div-inv 0.5

      \[\leadsto \cosh x \cdot \color{blue}{\left(y \cdot \frac{1}{x \cdot z}\right)}\]
3. Recombined 3 regimes into one program.

4. Final simplification 0.5

   \[\leadsto \begin{array}{l} \mathbf{if}\;z \le -0.48421412719263424:\\ \;\;\;\;\cosh x \cdot \frac{1}{\frac{x \cdot z}{y}}\\ \mathbf{elif}\;z \le 9.40222425595707568 \cdot 10^{29}:\\ \;\;\;\;\frac{\cosh x \cdot \frac{y}{z}}{x}\\ \mathbf{else}:\\ \;\;\;\;\cosh x \cdot \left(y \cdot \frac{1}{x \cdot z}\right)\\ \end{array}\]

Reproduce

herbie shell --seed 2020148 
(FPCore (x y z)
  :name "Linear.Quaternion:$ctan from linear-1.19.1.3"
  :precision binary64

  :herbie-target
  (if (< y -4.618902267687042e-52) (* (/ (/ y z) x) (cosh x)) (if (< y 1.0385305359351529e-39) (/ (/ (* (cosh x) y) x) z) (* (/ (/ y z) x) (cosh x))))

  (/ (* (cosh x) (/ y x)) z))