Average Error: 59.8 → 0.4
Time: 38.6s
Precision: 64
Internal Precision: 2432
\[\frac{1}{x} - \frac{1}{\tan x}\]
↓
\[(\left(\frac{1}{45} \cdot x\right) \cdot \left(x \cdot x\right) + \left(\frac{1}{3} \cdot x\right))_*\]

Error

Bits error versus x

Target

Original59.8
Target0.1
Herbie0.4
\[\begin{array}{l} \mathbf{if}\;\left|x\right| \lt 0.026:\\ \;\;\;\;\frac{x}{3} \cdot \left(1 + \frac{x \cdot x}{15}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x} - \frac{1}{\tan x}\\ \end{array}\]

Derivation

  1. Initial program 59.8

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

  2. Taylor expanded around 0 59.9

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

  3. Applied simplify0.4

    \[\leadsto \color{blue}{(\left(\frac{1}{45} \cdot x\right) \cdot \left(x \cdot x\right) + \left(\frac{1}{3} \cdot x\right))_*}\]

Runtime

Time bar (total: 38.6s)Debug logProfile

herbie shell --seed '#(1070258749 1877548225 2229079127 1588002776 3179087814 1886870650)' +o rules:numerics
(FPCore (x)
  :name "invcot (example 3.9)"
  :pre (and (< -0.026 x) (< x 0.026))

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

  (- (/ 1 x) (/ 1 (tan x))))