Average Error: 25.5 → 0.5
Time: 43.5s
Precision: 64
Internal Precision: 576
\[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}\]
\[\frac{a \cdot \frac{-d}{\sqrt{c^2 + d^2}^*} + b \cdot \left(\frac{1}{\sqrt{c^2 + d^2}^*} \cdot c\right)}{\sqrt{c^2 + d^2}^*}\]

Error

Bits error versus a

Bits error versus b

Bits error versus c

Bits error versus d

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original25.5
Target0.5
Herbie0.5
\[\begin{array}{l} \mathbf{if}\;\left|d\right| \lt \left|c\right|:\\ \;\;\;\;\frac{b - a \cdot \frac{d}{c}}{c + d \cdot \frac{d}{c}}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(-a\right) + b \cdot \frac{c}{d}}{d + c \cdot \frac{c}{d}}\\ \end{array}\]

Derivation

  1. Initial program 25.5

    \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}\]
  2. Using strategy rm
  3. Applied add-sqr-sqrt25.5

    \[\leadsto \frac{b \cdot c - a \cdot d}{\color{blue}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}}\]
  4. Applied *-un-lft-identity25.5

    \[\leadsto \frac{\color{blue}{1 \cdot \left(b \cdot c - a \cdot d\right)}}{\sqrt{c \cdot c + d \cdot d} \cdot \sqrt{c \cdot c + d \cdot d}}\]
  5. Applied times-frac25.5

    \[\leadsto \color{blue}{\frac{1}{\sqrt{c \cdot c + d \cdot d}} \cdot \frac{b \cdot c - a \cdot d}{\sqrt{c \cdot c + d \cdot d}}}\]
  6. Simplified25.5

    \[\leadsto \color{blue}{\frac{1}{\sqrt{c^2 + d^2}^*}} \cdot \frac{b \cdot c - a \cdot d}{\sqrt{c \cdot c + d \cdot d}}\]
  7. Simplified16.6

    \[\leadsto \frac{1}{\sqrt{c^2 + d^2}^*} \cdot \color{blue}{\frac{b \cdot c - a \cdot d}{\sqrt{c^2 + d^2}^*}}\]
  8. Using strategy rm
  9. Applied associate-*r/16.5

    \[\leadsto \color{blue}{\frac{\frac{1}{\sqrt{c^2 + d^2}^*} \cdot \left(b \cdot c - a \cdot d\right)}{\sqrt{c^2 + d^2}^*}}\]
  10. Using strategy rm
  11. Applied sub-neg16.5

    \[\leadsto \frac{\frac{1}{\sqrt{c^2 + d^2}^*} \cdot \color{blue}{\left(b \cdot c + \left(-a \cdot d\right)\right)}}{\sqrt{c^2 + d^2}^*}\]
  12. Applied distribute-rgt-in16.5

    \[\leadsto \frac{\color{blue}{\left(b \cdot c\right) \cdot \frac{1}{\sqrt{c^2 + d^2}^*} + \left(-a \cdot d\right) \cdot \frac{1}{\sqrt{c^2 + d^2}^*}}}{\sqrt{c^2 + d^2}^*}\]
  13. Simplified9.0

    \[\leadsto \frac{\left(b \cdot c\right) \cdot \frac{1}{\sqrt{c^2 + d^2}^*} + \color{blue}{\left(-a\right) \cdot \frac{d}{\sqrt{c^2 + d^2}^*}}}{\sqrt{c^2 + d^2}^*}\]
  14. Using strategy rm
  15. Applied associate-*l*0.5

    \[\leadsto \frac{\color{blue}{b \cdot \left(c \cdot \frac{1}{\sqrt{c^2 + d^2}^*}\right)} + \left(-a\right) \cdot \frac{d}{\sqrt{c^2 + d^2}^*}}{\sqrt{c^2 + d^2}^*}\]
  16. Final simplification0.5

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

Runtime

Time bar (total: 43.5s)Debug logProfile

herbie shell --seed 2018216 +o rules:numerics
(FPCore (a b c d)
  :name "Complex division, imag part"

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

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