Average Error: 37.0 → 14.0
Time: 12.3s
Precision: 64
Internal Precision: 128
\[0.5 \cdot \sqrt{2.0 \cdot \left(\sqrt{re \cdot re + im \cdot im} + re\right)}\]
\[0.5 \cdot \sqrt{(\left(\left(\left(\sqrt{\left|\sqrt[3]{\sqrt{re^2 + im^2}^*}\right|} \cdot \sqrt{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*}}}\right) \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right) \cdot \sqrt{\sqrt{\sqrt{re^2 + im^2}^*}}\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]

Error

Bits error versus re

Bits error versus im

Target

Original37.0
Target32.5
Herbie14.0
\[\begin{array}{l} \mathbf{if}\;re \lt 0:\\ \;\;\;\;0.5 \cdot \left(\sqrt{2} \cdot \sqrt{\frac{im \cdot im}{\sqrt{re \cdot re + im \cdot im} - re}}\right)\\ \mathbf{else}:\\ \;\;\;\;0.5 \cdot \sqrt{2.0 \cdot \left(\sqrt{re \cdot re + im \cdot im} + re\right)}\\ \end{array}\]

Derivation

  1. Initial program 37.0

    \[0.5 \cdot \sqrt{2.0 \cdot \left(\sqrt{re \cdot re + im \cdot im} + re\right)}\]
  2. Simplified12.5

    \[\leadsto \color{blue}{0.5 \cdot \sqrt{(\left(\sqrt{re^2 + im^2}^*\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}}\]
  3. Using strategy rm
  4. Applied add-sqr-sqrt13.5

    \[\leadsto 0.5 \cdot \sqrt{(\color{blue}{\left(\sqrt{\sqrt{re^2 + im^2}^*} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)} \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  5. Using strategy rm
  6. Applied add-sqr-sqrt13.8

    \[\leadsto 0.5 \cdot \sqrt{(\left(\color{blue}{\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \sqrt{\sqrt{\sqrt{re^2 + im^2}^*}}\right)} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  7. Applied associate-*l*13.8

    \[\leadsto 0.5 \cdot \sqrt{(\color{blue}{\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)\right)} \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  8. Using strategy rm
  9. Applied add-cube-cbrt13.8

    \[\leadsto 0.5 \cdot \sqrt{(\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \left(\sqrt{\sqrt{\color{blue}{\left(\sqrt[3]{\sqrt{re^2 + im^2}^*} \cdot \sqrt[3]{\sqrt{re^2 + im^2}^*}\right) \cdot \sqrt[3]{\sqrt{re^2 + im^2}^*}}}} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  10. Applied sqrt-prod13.8

    \[\leadsto 0.5 \cdot \sqrt{(\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \left(\sqrt{\color{blue}{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*} \cdot \sqrt[3]{\sqrt{re^2 + im^2}^*}} \cdot \sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*}}}} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  11. Applied sqrt-prod14.0

    \[\leadsto 0.5 \cdot \sqrt{(\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \left(\color{blue}{\left(\sqrt{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*} \cdot \sqrt[3]{\sqrt{re^2 + im^2}^*}}} \cdot \sqrt{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*}}}\right)} \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  12. Simplified14.0

    \[\leadsto 0.5 \cdot \sqrt{(\left(\sqrt{\sqrt{\sqrt{re^2 + im^2}^*}} \cdot \left(\left(\color{blue}{\sqrt{\left|\sqrt[3]{\sqrt{re^2 + im^2}^*}\right|}} \cdot \sqrt{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*}}}\right) \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right)\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]
  13. Final simplification14.0

    \[\leadsto 0.5 \cdot \sqrt{(\left(\left(\left(\sqrt{\left|\sqrt[3]{\sqrt{re^2 + im^2}^*}\right|} \cdot \sqrt{\sqrt{\sqrt[3]{\sqrt{re^2 + im^2}^*}}}\right) \cdot \sqrt{\sqrt{re^2 + im^2}^*}\right) \cdot \sqrt{\sqrt{\sqrt{re^2 + im^2}^*}}\right) \cdot 2.0 + \left(re \cdot 2.0\right))_*}\]

Reproduce

herbie shell --seed 2019030 +o rules:numerics
(FPCore (re im)
  :name "math.sqrt on complex, real part"

  :herbie-target
  (if (< re 0) (* 0.5 (* (sqrt 2) (sqrt (/ (* im im) (- (sqrt (+ (* re re) (* im im))) re))))) (* 0.5 (sqrt (* 2.0 (+ (sqrt (+ (* re re) (* im im))) re)))))

  (* 0.5 (sqrt (* 2.0 (+ (sqrt (+ (* re re) (* im im))) re)))))