Average Error: 25.8 → 13.1
Time: 34.5s
Precision: 64
Internal Precision: 128
\[\frac{a \cdot c + b \cdot d}{c \cdot c + d \cdot d}\]
\[\begin{array}{l} \mathbf{if}\;c \le -1.0108561403615378 \cdot 10^{+75}:\\ \;\;\;\;\frac{-a}{\sqrt{c^2 + d^2}^*}\\ \mathbf{elif}\;c \le 7.020069000953778 \cdot 10^{+131}:\\ \;\;\;\;\frac{\frac{1}{\frac{1}{(d \cdot b + \left(a \cdot c\right))_*} \cdot \sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}\\ \mathbf{else}:\\ \;\;\;\;\frac{a}{\sqrt{c^2 + d^2}^*}\\ \end{array}\]

Error

Bits error versus a

Bits error versus b

Bits error versus c

Bits error versus d

Target

Original25.8
Target0.5
Herbie13.1
\[\begin{array}{l} \mathbf{if}\;\left|d\right| \lt \left|c\right|:\\ \;\;\;\;\frac{a + b \cdot \frac{d}{c}}{c + d \cdot \frac{d}{c}}\\ \mathbf{else}:\\ \;\;\;\;\frac{b + a \cdot \frac{c}{d}}{d + c \cdot \frac{c}{d}}\\ \end{array}\]

Derivation

  1. Split input into 3 regimes
  2. if c < -1.0108561403615378e+75

    1. Initial program 36.9

      \[\frac{a \cdot c + b \cdot d}{c \cdot c + d \cdot d}\]
    2. Using strategy rm
    3. Applied add-sqr-sqrt36.9

      \[\leadsto \frac{a \cdot c + b \cdot d}{\color{blue}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}}\]
    4. Applied *-un-lft-identity36.9

      \[\leadsto \frac{\color{blue}{1 \cdot \left(a \cdot c + b \cdot d\right)}}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}\]
    5. Applied times-frac36.9

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c \cdot c + d \cdot d}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}}\]
    6. Simplified36.9

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c^2 + d^2}^*}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}\]
    7. Simplified25.7

      \[\leadsto \frac{1}{\sqrt{c^2 + d^2}^*} \cdot \color{blue}{\frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}\]
    8. Using strategy rm
    9. Applied associate-*l/25.6

      \[\leadsto \color{blue}{\frac{1 \cdot \frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}}\]
    10. Simplified25.6

      \[\leadsto \frac{\color{blue}{\frac{(d \cdot b + \left(c \cdot a\right))_*}{\sqrt{c^2 + d^2}^*}}}{\sqrt{c^2 + d^2}^*}\]
    11. Using strategy rm
    12. Applied *-un-lft-identity25.6

      \[\leadsto \frac{\frac{\color{blue}{1 \cdot (d \cdot b + \left(c \cdot a\right))_*}}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}\]
    13. Applied associate-/l*25.6

      \[\leadsto \frac{\color{blue}{\frac{1}{\frac{\sqrt{c^2 + d^2}^*}{(d \cdot b + \left(c \cdot a\right))_*}}}}{\sqrt{c^2 + d^2}^*}\]
    14. Taylor expanded around -inf 16.3

      \[\leadsto \frac{\color{blue}{-1 \cdot a}}{\sqrt{c^2 + d^2}^*}\]
    15. Simplified16.3

      \[\leadsto \frac{\color{blue}{-a}}{\sqrt{c^2 + d^2}^*}\]

    if -1.0108561403615378e+75 < c < 7.020069000953778e+131

    1. Initial program 18.5

      \[\frac{a \cdot c + b \cdot d}{c \cdot c + d \cdot d}\]
    2. Using strategy rm
    3. Applied add-sqr-sqrt18.5

      \[\leadsto \frac{a \cdot c + b \cdot d}{\color{blue}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}}\]
    4. Applied *-un-lft-identity18.5

      \[\leadsto \frac{\color{blue}{1 \cdot \left(a \cdot c + b \cdot d\right)}}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}\]
    5. Applied times-frac18.5

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c \cdot c + d \cdot d}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}}\]
    6. Simplified18.5

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c^2 + d^2}^*}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}\]
    7. Simplified11.4

      \[\leadsto \frac{1}{\sqrt{c^2 + d^2}^*} \cdot \color{blue}{\frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}\]
    8. Using strategy rm
    9. Applied associate-*l/11.3

      \[\leadsto \color{blue}{\frac{1 \cdot \frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}}\]
    10. Simplified11.3

      \[\leadsto \frac{\color{blue}{\frac{(d \cdot b + \left(c \cdot a\right))_*}{\sqrt{c^2 + d^2}^*}}}{\sqrt{c^2 + d^2}^*}\]
    11. Using strategy rm
    12. Applied *-un-lft-identity11.3

      \[\leadsto \frac{\frac{\color{blue}{1 \cdot (d \cdot b + \left(c \cdot a\right))_*}}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}\]
    13. Applied associate-/l*11.4

      \[\leadsto \frac{\color{blue}{\frac{1}{\frac{\sqrt{c^2 + d^2}^*}{(d \cdot b + \left(c \cdot a\right))_*}}}}{\sqrt{c^2 + d^2}^*}\]
    14. Using strategy rm
    15. Applied div-inv11.6

      \[\leadsto \frac{\frac{1}{\color{blue}{\sqrt{c^2 + d^2}^* \cdot \frac{1}{(d \cdot b + \left(c \cdot a\right))_*}}}}{\sqrt{c^2 + d^2}^*}\]

    if 7.020069000953778e+131 < c

    1. Initial program 42.7

      \[\frac{a \cdot c + b \cdot d}{c \cdot c + d \cdot d}\]
    2. Using strategy rm
    3. Applied add-sqr-sqrt42.7

      \[\leadsto \frac{a \cdot c + b \cdot d}{\color{blue}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}}\]
    4. Applied *-un-lft-identity42.7

      \[\leadsto \frac{\color{blue}{1 \cdot \left(a \cdot c + b \cdot d\right)}}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}\]
    5. Applied times-frac42.7

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c \cdot c + d \cdot d}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}}\]
    6. Simplified42.7

      \[\leadsto \color{blue}{\frac{1}{\sqrt{c^2 + d^2}^*}} \cdot \frac{a \cdot c + b \cdot d}{\sqrt{c \cdot c + d \cdot d}}\]
    7. Simplified28.6

      \[\leadsto \frac{1}{\sqrt{c^2 + d^2}^*} \cdot \color{blue}{\frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}\]
    8. Using strategy rm
    9. Applied associate-*l/28.5

      \[\leadsto \color{blue}{\frac{1 \cdot \frac{(a \cdot c + \left(b \cdot d\right))_*}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}}\]
    10. Simplified28.5

      \[\leadsto \frac{\color{blue}{\frac{(d \cdot b + \left(c \cdot a\right))_*}{\sqrt{c^2 + d^2}^*}}}{\sqrt{c^2 + d^2}^*}\]
    11. Taylor expanded around 0 15.4

      \[\leadsto \frac{\color{blue}{a}}{\sqrt{c^2 + d^2}^*}\]
  3. Recombined 3 regimes into one program.
  4. Final simplification13.1

    \[\leadsto \begin{array}{l} \mathbf{if}\;c \le -1.0108561403615378 \cdot 10^{+75}:\\ \;\;\;\;\frac{-a}{\sqrt{c^2 + d^2}^*}\\ \mathbf{elif}\;c \le 7.020069000953778 \cdot 10^{+131}:\\ \;\;\;\;\frac{\frac{1}{\frac{1}{(d \cdot b + \left(a \cdot c\right))_*} \cdot \sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}\\ \mathbf{else}:\\ \;\;\;\;\frac{a}{\sqrt{c^2 + d^2}^*}\\ \end{array}\]

Runtime

Time bar (total: 34.5s)Debug logProfile

herbie shell --seed 2018304 +o rules:numerics
(FPCore (a b c d)
  :name "Complex division, real part"

  :herbie-target
  (if (< (fabs d) (fabs c)) (/ (+ a (* b (/ d c))) (+ c (* d (/ d c)))) (/ (+ b (* a (/ c d))) (+ d (* c (/ c d)))))

  (/ (+ (* a c) (* b d)) (+ (* c c) (* d d))))