Average Error: 1.7 → 0.9
Time: 17.2s
Precision: 64
\[\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|\]
\[\begin{array}{l} \mathbf{if}\;x \le -3.239102902922398389619014729318862756466 \cdot 10^{124}:\\ \;\;\;\;\left|\mathsf{fma}\left(\frac{x}{y}, -z, \frac{4}{y} + \frac{x}{y}\right)\right|\\ \mathbf{elif}\;x \le 1.554015068869189362092407590282578679209 \cdot 10^{-127}:\\ \;\;\;\;\left|\frac{\left(x + 4\right) - x \cdot z}{y}\right|\\ \mathbf{else}:\\ \;\;\;\;\left|\frac{x + 4}{y} - x \cdot \frac{z}{y}\right|\\ \end{array}\]
\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|
\begin{array}{l}
\mathbf{if}\;x \le -3.239102902922398389619014729318862756466 \cdot 10^{124}:\\
\;\;\;\;\left|\mathsf{fma}\left(\frac{x}{y}, -z, \frac{4}{y} + \frac{x}{y}\right)\right|\\

\mathbf{elif}\;x \le 1.554015068869189362092407590282578679209 \cdot 10^{-127}:\\
\;\;\;\;\left|\frac{\left(x + 4\right) - x \cdot z}{y}\right|\\

\mathbf{else}:\\
\;\;\;\;\left|\frac{x + 4}{y} - x \cdot \frac{z}{y}\right|\\

\end{array}
double f(double x, double y, double z) {
        double r2956912 = x;
        double r2956913 = 4.0;
        double r2956914 = r2956912 + r2956913;
        double r2956915 = y;
        double r2956916 = r2956914 / r2956915;
        double r2956917 = r2956912 / r2956915;
        double r2956918 = z;
        double r2956919 = r2956917 * r2956918;
        double r2956920 = r2956916 - r2956919;
        double r2956921 = fabs(r2956920);
        return r2956921;
}

double f(double x, double y, double z) {
        double r2956922 = x;
        double r2956923 = -3.2391029029223984e+124;
        bool r2956924 = r2956922 <= r2956923;
        double r2956925 = y;
        double r2956926 = r2956922 / r2956925;
        double r2956927 = z;
        double r2956928 = -r2956927;
        double r2956929 = 4.0;
        double r2956930 = r2956929 / r2956925;
        double r2956931 = r2956930 + r2956926;
        double r2956932 = fma(r2956926, r2956928, r2956931);
        double r2956933 = fabs(r2956932);
        double r2956934 = 1.5540150688691894e-127;
        bool r2956935 = r2956922 <= r2956934;
        double r2956936 = r2956922 + r2956929;
        double r2956937 = r2956922 * r2956927;
        double r2956938 = r2956936 - r2956937;
        double r2956939 = r2956938 / r2956925;
        double r2956940 = fabs(r2956939);
        double r2956941 = r2956936 / r2956925;
        double r2956942 = r2956927 / r2956925;
        double r2956943 = r2956922 * r2956942;
        double r2956944 = r2956941 - r2956943;
        double r2956945 = fabs(r2956944);
        double r2956946 = r2956935 ? r2956940 : r2956945;
        double r2956947 = r2956924 ? r2956933 : r2956946;
        return r2956947;
}

Error

Bits error versus x

Bits error versus y

Bits error versus z

Derivation

  1. Split input into 3 regimes
  2. if x < -3.2391029029223984e+124

    1. Initial program 0.1

      \[\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|\]
    2. Using strategy rm
    3. Applied associate-*l/13.4

      \[\leadsto \left|\frac{x + 4}{y} - \color{blue}{\frac{x \cdot z}{y}}\right|\]
    4. Applied sub-div13.4

      \[\leadsto \left|\color{blue}{\frac{\left(x + 4\right) - x \cdot z}{y}}\right|\]
    5. Taylor expanded around 0 13.4

      \[\leadsto \left|\color{blue}{\left(\frac{x}{y} + 4 \cdot \frac{1}{y}\right) - \frac{x \cdot z}{y}}\right|\]
    6. Simplified0.1

      \[\leadsto \left|\color{blue}{\mathsf{fma}\left(\frac{x}{y}, -z, \frac{4}{y} + \frac{x}{y}\right)}\right|\]

    if -3.2391029029223984e+124 < x < 1.5540150688691894e-127

    1. Initial program 2.3

      \[\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|\]
    2. Using strategy rm
    3. Applied associate-*l/0.7

      \[\leadsto \left|\frac{x + 4}{y} - \color{blue}{\frac{x \cdot z}{y}}\right|\]
    4. Applied sub-div0.7

      \[\leadsto \left|\color{blue}{\frac{\left(x + 4\right) - x \cdot z}{y}}\right|\]

    if 1.5540150688691894e-127 < x

    1. Initial program 1.1

      \[\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|\]
    2. Using strategy rm
    3. Applied div-inv1.1

      \[\leadsto \left|\frac{x + 4}{y} - \color{blue}{\left(x \cdot \frac{1}{y}\right)} \cdot z\right|\]
    4. Applied associate-*l*1.6

      \[\leadsto \left|\frac{x + 4}{y} - \color{blue}{x \cdot \left(\frac{1}{y} \cdot z\right)}\right|\]
    5. Simplified1.6

      \[\leadsto \left|\frac{x + 4}{y} - x \cdot \color{blue}{\frac{z}{y}}\right|\]
  3. Recombined 3 regimes into one program.
  4. Final simplification0.9

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \le -3.239102902922398389619014729318862756466 \cdot 10^{124}:\\ \;\;\;\;\left|\mathsf{fma}\left(\frac{x}{y}, -z, \frac{4}{y} + \frac{x}{y}\right)\right|\\ \mathbf{elif}\;x \le 1.554015068869189362092407590282578679209 \cdot 10^{-127}:\\ \;\;\;\;\left|\frac{\left(x + 4\right) - x \cdot z}{y}\right|\\ \mathbf{else}:\\ \;\;\;\;\left|\frac{x + 4}{y} - x \cdot \frac{z}{y}\right|\\ \end{array}\]

Reproduce

herbie shell --seed 2019173 +o rules:numerics
(FPCore (x y z)
  :name "fabs fraction 1"
  (fabs (- (/ (+ x 4.0) y) (* (/ x y) z))))