Average Error: 30.0 → 0.3
Time: 1.9s
Precision: binary64
\[\sqrt{\left(2 \cdot x\right) \cdot x}\]
↓
\[\begin{array}{l} \mathbf{if}\;x \le -4.103081421486052 \cdot 10^{-310}:\\ \;\;\;\;\sqrt{\sqrt{\sqrt{2}}} \cdot \left(x \cdot \left(\sqrt{\sqrt{2}} \cdot \left(-\sqrt{\sqrt{\sqrt{2}}}\right)\right)\right)\\ \mathbf{else}:\\ \;\;\;\;\sqrt{x \cdot 2} \cdot \sqrt{x}\\ \end{array}\]

Error

Bits error versus x

Derivation

  1. Split input into 2 regimes

  2. if x < -4.103081421486052e-310

    1. Initial program 30.1

      \[\sqrt{\left(2 \cdot x\right) \cdot x}\]

    2. Taylor expanded around -inf 0.4

      \[\leadsto \color{blue}{-1 \cdot \left(\sqrt{2} \cdot x\right)}\]

    3. Simplified0.4

      \[\leadsto \color{blue}{x \cdot \left(-\sqrt{2}\right)}\]
    4. Using strategy rm

    5. Applied add-sqr-sqrt0.4

      \[\leadsto x \cdot \left(-\sqrt{\color{blue}{\sqrt{2} \cdot \sqrt{2}}}\right)\]

    6. Applied sqrt-prod0.6

      \[\leadsto x \cdot \left(-\color{blue}{\sqrt{\sqrt{2}} \cdot \sqrt{\sqrt{2}}}\right)\]

    7. Applied distribute-lft-neg-in0.6

      \[\leadsto x \cdot \color{blue}{\left(\left(-\sqrt{\sqrt{2}}\right) \cdot \sqrt{\sqrt{2}}\right)}\]

    8. Applied associate-*r*0.4

      \[\leadsto \color{blue}{\left(x \cdot \left(-\sqrt{\sqrt{2}}\right)\right) \cdot \sqrt{\sqrt{2}}}\]
    9. Using strategy rm

    10. Applied add-sqr-sqrt0.4

      \[\leadsto \left(x \cdot \left(-\sqrt{\sqrt{2}}\right)\right) \cdot \sqrt{\sqrt{\color{blue}{\sqrt{2} \cdot \sqrt{2}}}}\]

    11. Applied sqrt-prod0.4

      \[\leadsto \left(x \cdot \left(-\sqrt{\sqrt{2}}\right)\right) \cdot \sqrt{\color{blue}{\sqrt{\sqrt{2}} \cdot \sqrt{\sqrt{2}}}}\]

    12. Applied sqrt-prod0.4

      \[\leadsto \left(x \cdot \left(-\sqrt{\sqrt{2}}\right)\right) \cdot \color{blue}{\left(\sqrt{\sqrt{\sqrt{2}}} \cdot \sqrt{\sqrt{\sqrt{2}}}\right)}\]

    13. Applied associate-*r*0.4

      \[\leadsto \color{blue}{\left(\left(x \cdot \left(-\sqrt{\sqrt{2}}\right)\right) \cdot \sqrt{\sqrt{\sqrt{2}}}\right) \cdot \sqrt{\sqrt{\sqrt{2}}}}\]

    14. Simplified0.3

      \[\leadsto \color{blue}{\left(x \cdot \left(\sqrt{\sqrt{2}} \cdot \left(-\sqrt{\sqrt{\sqrt{2}}}\right)\right)\right)} \cdot \sqrt{\sqrt{\sqrt{2}}}\]

    if -4.103081421486052e-310 < x

    1. Initial program 30.0

      \[\sqrt{\left(2 \cdot x\right) \cdot x}\]
    2. Using strategy rm

    3. Applied sqrt-prod0.4

      \[\leadsto \color{blue}{\sqrt{2 \cdot x} \cdot \sqrt{x}}\]
  3. Recombined 2 regimes into one program.

  4. Final simplification0.3

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \le -4.103081421486052 \cdot 10^{-310}:\\ \;\;\;\;\sqrt{\sqrt{\sqrt{2}}} \cdot \left(x \cdot \left(\sqrt{\sqrt{2}} \cdot \left(-\sqrt{\sqrt{\sqrt{2}}}\right)\right)\right)\\ \mathbf{else}:\\ \;\;\;\;\sqrt{x \cdot 2} \cdot \sqrt{x}\\ \end{array}\]

Reproduce

herbie shell --seed 2020179 
(FPCore (x)
  :name "sqrt B"
  :precision binary64
  (sqrt (* (* 2.0 x) x)))