Average Error: 11.3 → 0.5
Time: 7.5s
Precision: binary64
\[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x}\]
↓
\[\begin{array}{l} \mathbf{if}\;x \leq -2.3049130861507487 \cdot 10^{+21} \lor \neg \left(x \leq 0.4586887196655391\right):\\ \;\;\;\;e^{-y} \cdot \frac{1}{x}\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x}\\ \end{array}\]
\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x}
↓
\begin{array}{l}
\mathbf{if}\;x \leq -2.3049130861507487 \cdot 10^{+21} \lor \neg \left(x \leq 0.4586887196655391\right):\\
\;\;\;\;e^{-y} \cdot \frac{1}{x}\\

\mathbf{else}:\\
\;\;\;\;\frac{1}{x}\\

\end{array}
(FPCore (x y) :precision binary64 (/ (exp (* x (log (/ x (+ x y))))) x))
↓
(FPCore (x y)
 :precision binary64
 (if (or (<= x -2.3049130861507487e+21) (not (<= x 0.4586887196655391)))
   (* (exp (- y)) (/ 1.0 x))
   (/ 1.0 x)))
double code(double x, double y) {
	return exp(x * log(x / (x + y))) / x;
}
↓
double code(double x, double y) {
	double tmp;
	if ((x <= -2.3049130861507487e+21) || !(x <= 0.4586887196655391)) {
		tmp = exp(-y) * (1.0 / x);
	} else {
		tmp = 1.0 / x;
	}
	return tmp;
}

Error

Bits error versus x

Bits error versus y

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original11.3
Target7.9
Herbie0.5
\[\begin{array}{l} \mathbf{if}\;y < -3.7311844206647956 \cdot 10^{+94}:\\ \;\;\;\;\frac{e^{\frac{-1}{y}}}{x}\\ \mathbf{elif}\;y < 2.817959242728288 \cdot 10^{+37}:\\ \;\;\;\;\frac{{\left(\frac{x}{y + x}\right)}^{x}}{x}\\ \mathbf{elif}\;y < 2.347387415166998 \cdot 10^{+178}:\\ \;\;\;\;\log \left(e^{\frac{{\left(\frac{x}{y + x}\right)}^{x}}{x}}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{e^{\frac{-1}{y}}}{x}\\ \end{array}\]

Derivation

  1. Split input into 2 regimes

  2. if x < -2304913086150748670000 or 0.458688719665539091 < x

    1. Initial program 11.2

      \[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x}\]

    2. Simplified11.2

      \[\leadsto \color{blue}{\frac{{\left(\frac{x}{x + y}\right)}^{x}}{x}}\]

    3. Taylor expanded around inf 0.1

      \[\leadsto \frac{\color{blue}{e^{-y}}}{x}\]
    4. Using strategy rm

    5. Applied div-inv_binary64_130330.1

      \[\leadsto \color{blue}{e^{-y} \cdot \frac{1}{x}}\]

    if -2304913086150748670000 < x < 0.458688719665539091

    1. Initial program 11.5

      \[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x}\]

    2. Simplified11.5

      \[\leadsto \color{blue}{\frac{{\left(\frac{x}{x + y}\right)}^{x}}{x}}\]

    3. Taylor expanded around 0 0.8

      \[\leadsto \frac{\color{blue}{1}}{x}\]
  3. Recombined 2 regimes into one program.

  4. Final simplification0.5

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \leq -2.3049130861507487 \cdot 10^{+21} \lor \neg \left(x \leq 0.4586887196655391\right):\\ \;\;\;\;e^{-y} \cdot \frac{1}{x}\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x}\\ \end{array}\]

Reproduce

herbie shell --seed 2021044 
(FPCore (x y)
  :name "Numeric.SpecFunctions:invIncompleteBetaWorker from math-functions-0.1.5.2, F"
  :precision binary64

  :herbie-target
  (if (< y -3.7311844206647956e+94) (/ (exp (/ -1.0 y)) x) (if (< y 2.817959242728288e+37) (/ (pow (/ x (+ y x)) x) x) (if (< y 2.347387415166998e+178) (log (exp (/ (pow (/ x (+ y x)) x) x))) (/ (exp (/ -1.0 y)) x))))

  (/ (exp (* x (log (/ x (+ x y))))) x))