Average Error: 0.5 → 0.5
Time: 21.6s
Precision: 64
Internal Precision: 128
\[\log \left(1 + e^{x}\right) - x \cdot y\]
\[{\left(\left(\log \left(e^{x} + 1\right) \cdot \left(\log \left(1 + {\left(e^{x}\right)}^{3}\right) - \log \left(\left(1 - e^{x}\right) + e^{x} \cdot e^{x}\right)\right)\right) \cdot \log \left(e^{x} + 1\right)\right)}^{\frac{1}{3}} - x \cdot y\]

Error

Bits error versus x

Bits error versus y

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Results

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Target

Original0.5
Target0.1
Herbie0.5
\[\begin{array}{l} \mathbf{if}\;x \le 0:\\ \;\;\;\;\log \left(1 + e^{x}\right) - x \cdot y\\ \mathbf{else}:\\ \;\;\;\;\log \left(1 + e^{-x}\right) - \left(-x\right) \cdot \left(1 - y\right)\\ \end{array}\]

Derivation

  1. Initial program 0.5

    \[\log \left(1 + e^{x}\right) - x \cdot y\]
  2. Initial simplification0.5

    \[\leadsto \log \left(1 + e^{x}\right) - y \cdot x\]
  3. Taylor expanded around inf 0.5

    \[\leadsto \log \color{blue}{\left(e^{x} + 1\right)} - y \cdot x\]
  4. Using strategy rm
  5. Applied add-cbrt-cube0.5

    \[\leadsto \color{blue}{\sqrt[3]{\left(\log \left(e^{x} + 1\right) \cdot \log \left(e^{x} + 1\right)\right) \cdot \log \left(e^{x} + 1\right)}} - y \cdot x\]
  6. Using strategy rm
  7. Applied flip3-+0.5

    \[\leadsto \sqrt[3]{\left(\log \left(e^{x} + 1\right) \cdot \log \color{blue}{\left(\frac{{\left(e^{x}\right)}^{3} + {1}^{3}}{e^{x} \cdot e^{x} + \left(1 \cdot 1 - e^{x} \cdot 1\right)}\right)}\right) \cdot \log \left(e^{x} + 1\right)} - y \cdot x\]
  8. Applied log-div0.5

    \[\leadsto \sqrt[3]{\left(\log \left(e^{x} + 1\right) \cdot \color{blue}{\left(\log \left({\left(e^{x}\right)}^{3} + {1}^{3}\right) - \log \left(e^{x} \cdot e^{x} + \left(1 \cdot 1 - e^{x} \cdot 1\right)\right)\right)}\right) \cdot \log \left(e^{x} + 1\right)} - y \cdot x\]
  9. Simplified0.5

    \[\leadsto \sqrt[3]{\left(\log \left(e^{x} + 1\right) \cdot \left(\color{blue}{\log \left(1 + {\left(e^{x}\right)}^{3}\right)} - \log \left(e^{x} \cdot e^{x} + \left(1 \cdot 1 - e^{x} \cdot 1\right)\right)\right)\right) \cdot \log \left(e^{x} + 1\right)} - y \cdot x\]
  10. Using strategy rm
  11. Applied pow1/30.5

    \[\leadsto \color{blue}{{\left(\left(\log \left(e^{x} + 1\right) \cdot \left(\log \left(1 + {\left(e^{x}\right)}^{3}\right) - \log \left(e^{x} \cdot e^{x} + \left(1 \cdot 1 - e^{x} \cdot 1\right)\right)\right)\right) \cdot \log \left(e^{x} + 1\right)\right)}^{\frac{1}{3}}} - y \cdot x\]
  12. Final simplification0.5

    \[\leadsto {\left(\left(\log \left(e^{x} + 1\right) \cdot \left(\log \left(1 + {\left(e^{x}\right)}^{3}\right) - \log \left(\left(1 - e^{x}\right) + e^{x} \cdot e^{x}\right)\right)\right) \cdot \log \left(e^{x} + 1\right)\right)}^{\frac{1}{3}} - x \cdot y\]

Runtime

Time bar (total: 21.6s)Debug logProfile

herbie shell --seed 2018304 
(FPCore (x y)
  :name "Logistic regression 2"

  :herbie-target
  (if (<= x 0) (- (log (+ 1 (exp x))) (* x y)) (- (log (+ 1 (exp (- x)))) (* (- x) (- 1 y))))

  (- (log (+ 1 (exp x))) (* x y)))