Average Error: 0.5 → 0.5
Time: 20.9s
Precision: 64
Internal Precision: 896
\[\log \left(1 + e^{x}\right) - x \cdot y\]
\[\begin{array}{l} \mathbf{if}\;x \le -9.040718665343158 \cdot 10^{-06}:\\ \;\;\;\;\log \left(\sqrt{1 + e^{x}}\right) + \left(\left(\log \left(\left|\sqrt[3]{1 + e^{x}}\right|\right) + \sqrt[3]{{\left(\log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)\right)}^{3}}\right) - x \cdot y\right)\\ \mathbf{if}\;x \le 2.7308670765476417 \cdot 10^{-09}:\\ \;\;\;\;\log \left(\frac{1}{2} \cdot {x}^{2} + \left(2 + x\right)\right) - x \cdot y\\ \mathbf{else}:\\ \;\;\;\;\log \left(\sqrt{1 + e^{x}}\right) + \left(\left(\log \left(\left|\sqrt[3]{1 + e^{x}}\right|\right) + \sqrt[3]{{\left(\log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)\right)}^{3}}\right) - x \cdot y\right)\\ \end{array}\]

Error

Bits error versus x

Bits error versus y

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. Split input into 2 regimes
  2. if x < -9.040718665343158e-06 or 2.7308670765476417e-09 < x

    1. Initial program 1.7

      \[\log \left(1 + e^{x}\right) - x \cdot y\]
    2. Using strategy rm
    3. Applied add-sqr-sqrt1.7

      \[\leadsto \log \color{blue}{\left(\sqrt{1 + e^{x}} \cdot \sqrt{1 + e^{x}}\right)} - x \cdot y\]
    4. Applied log-prod1.7

      \[\leadsto \color{blue}{\left(\log \left(\sqrt{1 + e^{x}}\right) + \log \left(\sqrt{1 + e^{x}}\right)\right)} - x \cdot y\]
    5. Applied associate--l+1.7

      \[\leadsto \color{blue}{\log \left(\sqrt{1 + e^{x}}\right) + \left(\log \left(\sqrt{1 + e^{x}}\right) - x \cdot y\right)}\]
    6. Using strategy rm
    7. Applied add-cube-cbrt1.7

      \[\leadsto \log \left(\sqrt{1 + e^{x}}\right) + \left(\log \left(\sqrt{\color{blue}{\left(\sqrt[3]{1 + e^{x}} \cdot \sqrt[3]{1 + e^{x}}\right) \cdot \sqrt[3]{1 + e^{x}}}}\right) - x \cdot y\right)\]
    8. Applied sqrt-prod1.7

      \[\leadsto \log \left(\sqrt{1 + e^{x}}\right) + \left(\log \color{blue}{\left(\sqrt{\sqrt[3]{1 + e^{x}} \cdot \sqrt[3]{1 + e^{x}}} \cdot \sqrt{\sqrt[3]{1 + e^{x}}}\right)} - x \cdot y\right)\]
    9. Applied log-prod1.7

      \[\leadsto \log \left(\sqrt{1 + e^{x}}\right) + \left(\color{blue}{\left(\log \left(\sqrt{\sqrt[3]{1 + e^{x}} \cdot \sqrt[3]{1 + e^{x}}}\right) + \log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)\right)} - x \cdot y\right)\]
    10. Applied simplify1.7

      \[\leadsto \log \left(\sqrt{1 + e^{x}}\right) + \left(\left(\color{blue}{\log \left(\left|\sqrt[3]{1 + e^{x}}\right|\right)} + \log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)\right) - x \cdot y\right)\]
    11. Using strategy rm
    12. Applied add-cbrt-cube1.7

      \[\leadsto \log \left(\sqrt{1 + e^{x}}\right) + \left(\left(\log \left(\left|\sqrt[3]{1 + e^{x}}\right|\right) + \color{blue}{\sqrt[3]{\left(\log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right) \cdot \log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)\right) \cdot \log \left(\sqrt{\sqrt[3]{1 + e^{x}}}\right)}}\right) - x \cdot y\right)\]
    13. Applied simplify1.7

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

    if -9.040718665343158e-06 < x < 2.7308670765476417e-09

    1. Initial program 0.0

      \[\log \left(1 + e^{x}\right) - x \cdot y\]
    2. Taylor expanded around 0 0.0

      \[\leadsto \log \color{blue}{\left(\frac{1}{2} \cdot {x}^{2} + \left(2 + x\right)\right)} - x \cdot y\]
  3. Recombined 2 regimes into one program.

Runtime

Time bar (total: 20.9s)Debug logProfile

herbie shell --seed '#(1070131407 1246090267 3027482374 2150728003 2026520792 2347815650)' 
(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)))