Average Error: 30.3 → 0.3
Time: 1.7m
Precision: 64
Ground Truth: 128
\[\frac{1 - \cos x}{{x}^2}\]
\[\begin{array}{l} \mathbf{if}\;x \le -7.829158115972637 \cdot 10^{-05}:\\ \;\;\;\;\frac{1}{x} \cdot \frac{1 - \cos x}{x}\\ \mathbf{if}\;x \le 2.576641619206354 \cdot 10^{-19}:\\ \;\;\;\;\left(\frac{1}{720} \cdot {x}^{4} + \frac{1}{2}\right) - \frac{1}{24} \cdot {x}^2\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x} \cdot \frac{\frac{{\left(\sin x\right)}^2}{1 + \cos x}}{x}\\ \end{array}\]

Error

Bits error versus x

Derivation

  1. Split input into 3 regimes.
  2. if x < -7.829158115972637e-05

    1. Initial program 1.3

      \[\frac{1 - \cos x}{{x}^2}\]
    2. Using strategy rm
    3. Applied square-mult 1.3

      \[\leadsto \frac{1 - \cos x}{\color{blue}{x \cdot x}}\]
    4. Applied *-un-lft-identity 1.3

      \[\leadsto \frac{\color{blue}{1 \cdot \left(1 - \cos x\right)}}{x \cdot x}\]
    5. Applied times-frac 0.6

      \[\leadsto \color{blue}{\frac{1}{x} \cdot \frac{1 - \cos x}{x}}\]

    if -7.829158115972637e-05 < x < 2.576641619206354e-19

    1. Initial program 61.9

      \[\frac{1 - \cos x}{{x}^2}\]
    2. Applied taylor 0

      \[\leadsto \left(\frac{1}{720} \cdot {x}^{4} + \frac{1}{2}\right) - \frac{1}{24} \cdot {x}^2\]
    3. Taylor expanded around 0 0

      \[\leadsto \color{blue}{\left(\frac{1}{720} \cdot {x}^{4} + \frac{1}{2}\right) - \frac{1}{24} \cdot {x}^2}\]

    if 2.576641619206354e-19 < x

    1. Initial program 3.3

      \[\frac{1 - \cos x}{{x}^2}\]
    2. Using strategy rm
    3. Applied flip-- 3.5

      \[\leadsto \frac{\color{blue}{\frac{{1}^2 - {\left(\cos x\right)}^2}{1 + \cos x}}}{{x}^2}\]
    4. Applied simplify 1.1

      \[\leadsto \frac{\frac{\color{blue}{{\left(\sin x\right)}^2}}{1 + \cos x}}{{x}^2}\]
    5. Using strategy rm
    6. Applied square-mult 1.1

      \[\leadsto \frac{\frac{{\left(\sin x\right)}^2}{1 + \cos x}}{\color{blue}{x \cdot x}}\]
    7. Applied *-un-lft-identity 1.1

      \[\leadsto \frac{\frac{{\left(\sin x\right)}^2}{\color{blue}{1 \cdot \left(1 + \cos x\right)}}}{x \cdot x}\]
    8. Applied *-un-lft-identity 1.1

      \[\leadsto \frac{\frac{{\color{blue}{\left(1 \cdot \sin x\right)}}^2}{1 \cdot \left(1 + \cos x\right)}}{x \cdot x}\]
    9. Applied square-prod 1.1

      \[\leadsto \frac{\frac{\color{blue}{{1}^2 \cdot {\left(\sin x\right)}^2}}{1 \cdot \left(1 + \cos x\right)}}{x \cdot x}\]
    10. Applied times-frac 1.1

      \[\leadsto \frac{\color{blue}{\frac{{1}^2}{1} \cdot \frac{{\left(\sin x\right)}^2}{1 + \cos x}}}{x \cdot x}\]
    11. Applied times-frac 0.5

      \[\leadsto \color{blue}{\frac{\frac{{1}^2}{1}}{x} \cdot \frac{\frac{{\left(\sin x\right)}^2}{1 + \cos x}}{x}}\]
    12. Applied simplify 0.5

      \[\leadsto \color{blue}{\frac{1}{x}} \cdot \frac{\frac{{\left(\sin x\right)}^2}{1 + \cos x}}{x}\]
  3. Recombined 3 regimes into one program.
  4. Removed slow pow expressions

Runtime

Total time: 1.7m Debug log

Please include this information when filing a bug report:

herbie --seed '#(2844525053 3990250133 247123594 353958486 2001714664 3183081771)'
(FPCore (x)
  :name "NMSE problem 3.4.1"
  (/ (- 1 (cos x)) (sqr x)))