Average Error: 13.7 → 1.2
Time: 41.4s
Precision: 64
Internal Precision: 128
\[wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}}\]
\[\left(\left(wj \cdot wj + \left(1 - wj\right)\right) \cdot \frac{\frac{1}{e^{wj}}}{1 + {wj}^{3}}\right) \cdot x + \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right)\]

Error

Bits error versus wj

Bits error versus x

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Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original13.7
Target13.0
Herbie1.2
\[wj - \left(\frac{wj}{wj + 1} - \frac{x}{e^{wj} + wj \cdot e^{wj}}\right)\]

Derivation

  1. Initial program 13.7

    \[wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}}\]
  2. Initial simplification6.7

    \[\leadsto \left(wj - \frac{wj}{wj + 1}\right) + \frac{\frac{x}{e^{wj}}}{wj + 1}\]
  3. Taylor expanded around 0 1.2

    \[\leadsto \color{blue}{\left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right)} + \frac{\frac{x}{e^{wj}}}{wj + 1}\]
  4. Using strategy rm
  5. Applied *-un-lft-identity1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + \frac{\frac{x}{e^{wj}}}{\color{blue}{1 \cdot \left(wj + 1\right)}}\]
  6. Applied div-inv1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + \frac{\color{blue}{x \cdot \frac{1}{e^{wj}}}}{1 \cdot \left(wj + 1\right)}\]
  7. Applied times-frac1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + \color{blue}{\frac{x}{1} \cdot \frac{\frac{1}{e^{wj}}}{wj + 1}}\]
  8. Simplified1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + \color{blue}{x} \cdot \frac{\frac{1}{e^{wj}}}{wj + 1}\]
  9. Using strategy rm
  10. Applied flip3-+1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + x \cdot \frac{\frac{1}{e^{wj}}}{\color{blue}{\frac{{wj}^{3} + {1}^{3}}{wj \cdot wj + \left(1 \cdot 1 - wj \cdot 1\right)}}}\]
  11. Applied associate-/r/1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + x \cdot \color{blue}{\left(\frac{\frac{1}{e^{wj}}}{{wj}^{3} + {1}^{3}} \cdot \left(wj \cdot wj + \left(1 \cdot 1 - wj \cdot 1\right)\right)\right)}\]
  12. Simplified1.2

    \[\leadsto \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right) + x \cdot \left(\frac{\frac{1}{e^{wj}}}{{wj}^{3} + {1}^{3}} \cdot \color{blue}{\left(\left(1 - wj\right) + wj \cdot wj\right)}\right)\]
  13. Final simplification1.2

    \[\leadsto \left(\left(wj \cdot wj + \left(1 - wj\right)\right) \cdot \frac{\frac{1}{e^{wj}}}{1 + {wj}^{3}}\right) \cdot x + \left(\left({wj}^{2} + {wj}^{4}\right) - {wj}^{3}\right)\]

Runtime

Time bar (total: 41.4s)Debug logProfile

herbie shell --seed 2018278 
(FPCore (wj x)
  :name "Jmat.Real.lambertw, newton loop step"

  :herbie-target
  (- wj (- (/ wj (+ wj 1)) (/ x (+ (exp wj) (* wj (exp wj))))))

  (- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))