Average Error: 9.8 → 0.1
Time: 3.7m
Precision: 64
Ground Truth: 128
\[\left(\frac{1}{x + 1} - \frac{2}{x}\right) + \frac{1}{x - 1}\]
\[\frac{\frac{2}{1 + x}}{\left(x - 1\right) \cdot x}\]

Error

Bits error versus x

Target

Original9.8
Comparison0.3
Herbie0.1
\[ \frac{2}{x \cdot \left({x}^2 - 1\right)} \]

Derivation

  1. Initial program 9.8

    \[\left(\frac{1}{x + 1} - \frac{2}{x}\right) + \frac{1}{x - 1}\]
  2. Using strategy rm
  3. Applied frac-sub 25.7

    \[\leadsto \color{blue}{\frac{1 \cdot x - \left(x + 1\right) \cdot 2}{\left(x + 1\right) \cdot x}} + \frac{1}{x - 1}\]
  4. Applied frac-add 25.1

    \[\leadsto \color{blue}{\frac{\left(1 \cdot x - \left(x + 1\right) \cdot 2\right) \cdot \left(x - 1\right) + \left(\left(x + 1\right) \cdot x\right) \cdot 1}{\left(\left(x + 1\right) \cdot x\right) \cdot \left(x - 1\right)}}\]
  5. Applied simplify 25.2

    \[\leadsto \frac{\color{blue}{\left(x - 1\right) \cdot \left(\left(x - 2\right) - \left(x + x\right)\right) + \left(x \cdot x + x\right)}}{\left(\left(x + 1\right) \cdot x\right) \cdot \left(x - 1\right)}\]
  6. Applied taylor 25.1

    \[\leadsto \frac{\left(2 - \left({x}^2 + x\right)\right) + \left(x \cdot x + x\right)}{\left(\left(x + 1\right) \cdot x\right) \cdot \left(x - 1\right)}\]
  7. Taylor expanded around 0 25.1

    \[\leadsto \frac{\color{blue}{\left(2 - \left({x}^2 + x\right)\right)} + \left(x \cdot x + x\right)}{\left(\left(x + 1\right) \cdot x\right) \cdot \left(x - 1\right)}\]
  8. Applied simplify 0.1

    \[\leadsto \color{blue}{\frac{\frac{2}{1 + x}}{\left(x - 1\right) \cdot x}}\]
  9. Removed slow pow expressions

Runtime

Total time: 3.7m Debug log

Please include this information when filing a bug report:

herbie --seed '#(3627917785 4173850852 207761465 1073084077 2889720686 475523375)'
(FPCore (x)
  :name "NMSE problem 3.3.3"

  :target
  (/ 2 (* x (- (sqr x) 1)))

  (+ (- (/ 1 (+ x 1)) (/ 2 x)) (/ 1 (- x 1))))