Linear.Quaternion:$ctan from linear-1.19.1.3

Average Error: 7.9 → 0.6

Time: 3.8s

Precision: binary64

Math

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

↓

\[\begin{array}{l} \mathbf{if}\;\cosh x \cdot \frac{y}{x} = -inf.0:\\ \;\;\;\;\frac{\cosh x}{x \cdot z} \cdot y\\ \mathbf{elif}\;\cosh x \cdot \frac{y}{x} \le 1.19242230315839987 \cdot 10^{155}:\\ \;\;\;\;\left(\cosh x \cdot \frac{y}{x}\right) \cdot \frac{1}{z}\\ \mathbf{else}:\\ \;\;\;\;\frac{\cosh x \cdot \frac{y}{z}}{x}\\ \end{array}\]

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 ((((double) (((double) cosh(x)) * ((double) (y / x)))) <= -inf.0)) {
		VAR = ((double) (((double) (((double) cosh(x)) / ((double) (x * z)))) * y));
	} else {
		double VAR_1;
		if ((((double) (((double) cosh(x)) * ((double) (y / x)))) <= 1.1924223031583999e+155)) {
			VAR_1 = ((double) (((double) (((double) cosh(x)) * ((double) (y / x)))) * ((double) (1.0 / z))));
		} else {
			VAR_1 = ((double) (((double) (((double) cosh(x)) * ((double) (y / z)))) / x));
		}
		VAR = VAR_1;
	}
	return VAR;
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Target

Original	7.9
Target	0.4
Herbie	0.6

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

Derivation

1. Split input into 3 regimes

2. if (* (cosh x) (/ y x)) < -inf.0

   1. Initial program 64.0

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

   3. Applied *-un-lft-identity 64.0

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

   4. Applied times-frac 64.0

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

   5. Simplified 64.0

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

   6. Simplified 0.7

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

   8. Applied clear-num 0.8

      \[\leadsto \cosh x \cdot \color{blue}{\frac{1}{\frac{x \cdot z}{y}}}\]
   9. Using strategy rm

   10. Applied associate-/r/ 0.8

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

   11. Applied associate-*r* 0.8

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

   12. Simplified 0.8

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

   if -inf.0 < (* (cosh x) (/ y x)) < 1.19242230315839987e155

   1. Initial program 0.2

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

   3. Applied div-inv 0.3

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

   if 1.19242230315839987e155 < (* (cosh x) (/ y x))

   1. Initial program 22.2

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

   3. Applied *-un-lft-identity 22.2

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

   4. Applied times-frac 22.1

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

   5. Simplified 22.1

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

   6. Simplified 1.5

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

   8. Applied *-un-lft-identity 1.5

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

   9. Applied times-frac 1.5

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

   10. Applied associate-*r* 1.6

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

   11. Simplified 1.5

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

   13. Applied associate-*l/ 1.4

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

4. Final simplification 0.6

   \[\leadsto \begin{array}{l} \mathbf{if}\;\cosh x \cdot \frac{y}{x} = -inf.0:\\ \;\;\;\;\frac{\cosh x}{x \cdot z} \cdot y\\ \mathbf{elif}\;\cosh x \cdot \frac{y}{x} \le 1.19242230315839987 \cdot 10^{155}:\\ \;\;\;\;\left(\cosh x \cdot \frac{y}{x}\right) \cdot \frac{1}{z}\\ \mathbf{else}:\\ \;\;\;\;\frac{\cosh x \cdot \frac{y}{z}}{x}\\ \end{array}\]

Reproduce

herbie shell --seed 2020171 
(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))