Average Error: 58.6 → 3.7
Time: 51.4s
Precision: 64
\[-1 \lt \varepsilon \land \varepsilon \lt 1\]
\[\frac{\varepsilon \cdot \left(e^{\left(a + b\right) \cdot \varepsilon} - 1\right)}{\left(e^{a \cdot \varepsilon} - 1\right) \cdot \left(e^{b \cdot \varepsilon} - 1\right)}\]
\[\begin{array}{l} \mathbf{if}\;b \le 1.2596314720077241 \cdot 10^{+207}:\\ \;\;\;\;\frac{1}{a} + \frac{1}{b}\\ \mathbf{else}:\\ \;\;\;\;\frac{\frac{\mathsf{expm1}\left(\left(\left(b + a\right) \cdot \varepsilon\right)\right) \cdot \varepsilon}{\mathsf{expm1}\left(\left(a \cdot \varepsilon\right)\right)}}{\mathsf{expm1}\left(\left(b \cdot \varepsilon\right)\right)}\\ \end{array}\]
\frac{\varepsilon \cdot \left(e^{\left(a + b\right) \cdot \varepsilon} - 1\right)}{\left(e^{a \cdot \varepsilon} - 1\right) \cdot \left(e^{b \cdot \varepsilon} - 1\right)}
\begin{array}{l}
\mathbf{if}\;b \le 1.2596314720077241 \cdot 10^{+207}:\\
\;\;\;\;\frac{1}{a} + \frac{1}{b}\\

\mathbf{else}:\\
\;\;\;\;\frac{\frac{\mathsf{expm1}\left(\left(\left(b + a\right) \cdot \varepsilon\right)\right) \cdot \varepsilon}{\mathsf{expm1}\left(\left(a \cdot \varepsilon\right)\right)}}{\mathsf{expm1}\left(\left(b \cdot \varepsilon\right)\right)}\\

\end{array}
double f(double a, double b, double eps) {
        double r7100252 = eps;
        double r7100253 = a;
        double r7100254 = b;
        double r7100255 = r7100253 + r7100254;
        double r7100256 = r7100255 * r7100252;
        double r7100257 = exp(r7100256);
        double r7100258 = 1.0;
        double r7100259 = r7100257 - r7100258;
        double r7100260 = r7100252 * r7100259;
        double r7100261 = r7100253 * r7100252;
        double r7100262 = exp(r7100261);
        double r7100263 = r7100262 - r7100258;
        double r7100264 = r7100254 * r7100252;
        double r7100265 = exp(r7100264);
        double r7100266 = r7100265 - r7100258;
        double r7100267 = r7100263 * r7100266;
        double r7100268 = r7100260 / r7100267;
        return r7100268;
}

double f(double a, double b, double eps) {
        double r7100269 = b;
        double r7100270 = 1.2596314720077241e+207;
        bool r7100271 = r7100269 <= r7100270;
        double r7100272 = 1.0;
        double r7100273 = a;
        double r7100274 = r7100272 / r7100273;
        double r7100275 = r7100272 / r7100269;
        double r7100276 = r7100274 + r7100275;
        double r7100277 = r7100269 + r7100273;
        double r7100278 = eps;
        double r7100279 = r7100277 * r7100278;
        double r7100280 = expm1(r7100279);
        double r7100281 = r7100280 * r7100278;
        double r7100282 = r7100273 * r7100278;
        double r7100283 = expm1(r7100282);
        double r7100284 = r7100281 / r7100283;
        double r7100285 = r7100269 * r7100278;
        double r7100286 = expm1(r7100285);
        double r7100287 = r7100284 / r7100286;
        double r7100288 = r7100271 ? r7100276 : r7100287;
        return r7100288;
}

Error

Bits error versus a

Bits error versus b

Bits error versus eps

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original58.6
Target13.7
Herbie3.7
\[\frac{a + b}{a \cdot b}\]

Derivation

  1. Split input into 2 regimes
  2. if b < 1.2596314720077241e+207

    1. Initial program 59.2

      \[\frac{\varepsilon \cdot \left(e^{\left(a + b\right) \cdot \varepsilon} - 1\right)}{\left(e^{a \cdot \varepsilon} - 1\right) \cdot \left(e^{b \cdot \varepsilon} - 1\right)}\]
    2. Simplified35.0

      \[\leadsto \color{blue}{\frac{\frac{\mathsf{expm1}\left(\left(\left(a + b\right) \cdot \varepsilon\right)\right) \cdot \varepsilon}{\mathsf{expm1}\left(\left(\varepsilon \cdot a\right)\right)}}{\mathsf{expm1}\left(\left(\varepsilon \cdot b\right)\right)}}\]
    3. Taylor expanded around 0 2.7

      \[\leadsto \color{blue}{\frac{1}{a} + \frac{1}{b}}\]

    if 1.2596314720077241e+207 < b

    1. Initial program 49.1

      \[\frac{\varepsilon \cdot \left(e^{\left(a + b\right) \cdot \varepsilon} - 1\right)}{\left(e^{a \cdot \varepsilon} - 1\right) \cdot \left(e^{b \cdot \varepsilon} - 1\right)}\]
    2. Simplified18.5

      \[\leadsto \color{blue}{\frac{\frac{\mathsf{expm1}\left(\left(\left(a + b\right) \cdot \varepsilon\right)\right) \cdot \varepsilon}{\mathsf{expm1}\left(\left(\varepsilon \cdot a\right)\right)}}{\mathsf{expm1}\left(\left(\varepsilon \cdot b\right)\right)}}\]
    3. Taylor expanded around -inf 22.4

      \[\leadsto \frac{\frac{\color{blue}{\left(e^{\left(a + b\right) \cdot \varepsilon} - 1\right) \cdot \varepsilon}}{\mathsf{expm1}\left(\left(\varepsilon \cdot a\right)\right)}}{\mathsf{expm1}\left(\left(\varepsilon \cdot b\right)\right)}\]
    4. Simplified18.5

      \[\leadsto \frac{\frac{\color{blue}{\varepsilon \cdot \mathsf{expm1}\left(\left(\left(b + a\right) \cdot \varepsilon\right)\right)}}{\mathsf{expm1}\left(\left(\varepsilon \cdot a\right)\right)}}{\mathsf{expm1}\left(\left(\varepsilon \cdot b\right)\right)}\]
  3. Recombined 2 regimes into one program.
  4. Final simplification3.7

    \[\leadsto \begin{array}{l} \mathbf{if}\;b \le 1.2596314720077241 \cdot 10^{+207}:\\ \;\;\;\;\frac{1}{a} + \frac{1}{b}\\ \mathbf{else}:\\ \;\;\;\;\frac{\frac{\mathsf{expm1}\left(\left(\left(b + a\right) \cdot \varepsilon\right)\right) \cdot \varepsilon}{\mathsf{expm1}\left(\left(a \cdot \varepsilon\right)\right)}}{\mathsf{expm1}\left(\left(b \cdot \varepsilon\right)\right)}\\ \end{array}\]

Reproduce

herbie shell --seed 2019120 +o rules:numerics
(FPCore (a b eps)
  :name "expq3 (problem 3.4.2)"
  :pre (and (< -1 eps) (< eps 1))

  :herbie-target
  (/ (+ a b) (* a b))

  (/ (* eps (- (exp (* (+ a b) eps)) 1)) (* (- (exp (* a eps)) 1) (- (exp (* b eps)) 1))))