Average Error: 59.9 → 0.3
Time: 26.4s
Precision: 64
Ground Truth: 128
\[\frac{1}{x} - \cot x\]
⬇
\[\frac{1}{45} \cdot {x}^3 + \left({x}^{5} \cdot \frac{2}{945} + x \cdot \frac{1}{3}\right)\]

Error

Bits error versus x

Target

Original59.9
Comparison0.1
Herbie0.3
\[ \begin{array}{l} \mathbf{if}\;\left|x\right| \lt 0.026:\\ \;\;\;\;\frac{x}{3} \cdot \left(1 + \frac{{x}^2}{15}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x} - \cot x\\ \end{array} \]

Derivation

  1. Initial program 59.9

    \[\frac{1}{x} - \cot x\]

  2. Applied taylor 0.3

    \[\leadsto \frac{1}{45} \cdot {x}^{3} + \left(\frac{2}{945} \cdot {x}^{5} + \frac{1}{3} \cdot x\right)\]

  3. Taylor expanded around 0 0.3

    \[\leadsto \color{blue}{\frac{1}{45} \cdot {x}^{3} + \left(\frac{2}{945} \cdot {x}^{5} + \frac{1}{3} \cdot x\right)}\]

  4. Applied simplify 0.3

    \[\leadsto \color{blue}{\frac{1}{45} \cdot {x}^3 + \left({x}^{5} \cdot \frac{2}{945} + x \cdot \frac{1}{3}\right)}\]
  5. Removed slow pow expressions

Runtime

Total time: 26.4s Debug log

Please include this information when filing a bug report:

herbie --seed '#(1908604153 1025457288 2462184406 4202787950 1290802251 2071818630)'
(FPCore (x)
  :name "NMSE example 3.9"
  :pre (and (< -0.026 x) (< x 0.026))

  :target
  (if (< (fabs x) 0.026) (* (/ x 3) (+ 1 (/ (sqr x) 15))) (- (/ 1 x) (cotan x)))

  (- (/ 1 x) (cotan x)))