Average Error: 58.5 → 0.4
Time: 17.0s
Precision: 64
Internal Precision: 128
\[e^{x} - 1\]
\[\frac{\left(\left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) \cdot \left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) + \frac{-1}{4}\right) \cdot \left(\left(1 + e^{x} \cdot \sqrt{e^{x}}\right) \cdot x\right)}{\left(\frac{-1}{2} + \left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) + \left(\frac{-1}{2} + \left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) \cdot \left(e^{x} - \sqrt{e^{x}}\right)}\]

Error

Bits error versus x

Target

Original58.5
Target0.5
Herbie0.4
\[x \cdot \left(\left(1 + \frac{x}{2}\right) + \frac{x \cdot x}{6}\right)\]

Derivation

  1. Initial program 58.5

    \[e^{x} - 1\]
  2. Using strategy rm
  3. Applied add-sqr-sqrt58.6

    \[\leadsto \color{blue}{\sqrt{e^{x}} \cdot \sqrt{e^{x}}} - 1\]
  4. Applied difference-of-sqr-158.6

    \[\leadsto \color{blue}{\left(\sqrt{e^{x}} + 1\right) \cdot \left(\sqrt{e^{x}} - 1\right)}\]
  5. Taylor expanded around 0 0.4

    \[\leadsto \left(\sqrt{e^{x}} + 1\right) \cdot \color{blue}{\left(\frac{1}{2} \cdot x + \left(\frac{1}{48} \cdot {x}^{3} + \frac{1}{8} \cdot {x}^{2}\right)\right)}\]
  6. Simplified0.4

    \[\leadsto \left(\sqrt{e^{x}} + 1\right) \cdot \color{blue}{\left(\left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) + \frac{1}{2}\right) \cdot x\right)}\]
  7. Using strategy rm
  8. Applied flip-+0.4

    \[\leadsto \left(\sqrt{e^{x}} + 1\right) \cdot \left(\color{blue}{\frac{\left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) - \frac{1}{2} \cdot \frac{1}{2}}{x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) - \frac{1}{2}}} \cdot x\right)\]
  9. Applied associate-*l/0.4

    \[\leadsto \left(\sqrt{e^{x}} + 1\right) \cdot \color{blue}{\frac{\left(\left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) - \frac{1}{2} \cdot \frac{1}{2}\right) \cdot x}{x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) - \frac{1}{2}}}\]
  10. Applied flip3-+0.4

    \[\leadsto \color{blue}{\frac{{\left(\sqrt{e^{x}}\right)}^{3} + {1}^{3}}{\sqrt{e^{x}} \cdot \sqrt{e^{x}} + \left(1 \cdot 1 - \sqrt{e^{x}} \cdot 1\right)}} \cdot \frac{\left(\left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) - \frac{1}{2} \cdot \frac{1}{2}\right) \cdot x}{x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) - \frac{1}{2}}\]
  11. Applied frac-times0.4

    \[\leadsto \color{blue}{\frac{\left({\left(\sqrt{e^{x}}\right)}^{3} + {1}^{3}\right) \cdot \left(\left(\left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right)\right) - \frac{1}{2} \cdot \frac{1}{2}\right) \cdot x\right)}{\left(\sqrt{e^{x}} \cdot \sqrt{e^{x}} + \left(1 \cdot 1 - \sqrt{e^{x}} \cdot 1\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) - \frac{1}{2}\right)}}\]
  12. Simplified0.4

    \[\leadsto \frac{\color{blue}{\left(\left(1 + \sqrt{e^{x}} \cdot e^{x}\right) \cdot x\right) \cdot \left(\left(\left(\frac{1}{8} + x \cdot \frac{1}{48}\right) \cdot x\right) \cdot \left(\left(\frac{1}{8} + x \cdot \frac{1}{48}\right) \cdot x\right) + \frac{-1}{4}\right)}}{\left(\sqrt{e^{x}} \cdot \sqrt{e^{x}} + \left(1 \cdot 1 - \sqrt{e^{x}} \cdot 1\right)\right) \cdot \left(x \cdot \left(\frac{1}{48} \cdot x + \frac{1}{8}\right) - \frac{1}{2}\right)}\]
  13. Simplified0.4

    \[\leadsto \frac{\left(\left(1 + \sqrt{e^{x}} \cdot e^{x}\right) \cdot x\right) \cdot \left(\left(\left(\frac{1}{8} + x \cdot \frac{1}{48}\right) \cdot x\right) \cdot \left(\left(\frac{1}{8} + x \cdot \frac{1}{48}\right) \cdot x\right) + \frac{-1}{4}\right)}{\color{blue}{\left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x + \frac{-1}{2}\right) + \left(e^{x} - \sqrt{e^{x}}\right) \cdot \left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x + \frac{-1}{2}\right)}}\]
  14. Final simplification0.4

    \[\leadsto \frac{\left(\left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) \cdot \left(\left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) + \frac{-1}{4}\right) \cdot \left(\left(1 + e^{x} \cdot \sqrt{e^{x}}\right) \cdot x\right)}{\left(\frac{-1}{2} + \left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) + \left(\frac{-1}{2} + \left(\frac{1}{8} + \frac{1}{48} \cdot x\right) \cdot x\right) \cdot \left(e^{x} - \sqrt{e^{x}}\right)}\]

Reproduce

herbie shell --seed 2019068 
(FPCore (x)
  :name "expm1 (example 3.7)"
  :pre (< -0.00017 x)

  :herbie-target
  (* x (+ (+ 1 (/ x 2)) (/ (* x x) 6)))

  (- (exp x) 1))