Average Error: 59.6 → 2.4
Time: 3.2m
Precision: 64
Internal Precision: 1344
\[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)\]
\[\left(\log \left((\frac{1}{12} \cdot \left(f \cdot \pi\right) + \left(\frac{\frac{4}{\pi}}{f}\right))_* - \left(\left(f \cdot \pi\right) \cdot \left(\pi \cdot \pi\right)\right) \cdot \left(\frac{1}{2880} \cdot \left(f \cdot f\right)\right)\right) \cdot \left(-\sqrt{\frac{4}{\pi}}\right)\right) \cdot \sqrt{\frac{4}{\pi}}\]

Error

Bits error versus f

Derivation

  1. Initial program 59.6

    \[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)\]
  2. Taylor expanded around 0 2.4

    \[\leadsto -\frac{1}{\frac{\pi}{4}} \cdot \log \color{blue}{\left(\left(\frac{1}{12} \cdot \left(\pi \cdot f\right) + 4 \cdot \frac{1}{\pi \cdot f}\right) - \frac{1}{2880} \cdot \left({\pi}^{3} \cdot {f}^{3}\right)\right)}\]
  3. Applied simplify2.4

    \[\leadsto \color{blue}{\log \left((\frac{1}{12} \cdot \left(f \cdot \pi\right) + \left(\frac{\frac{4}{\pi}}{f}\right))_* - \left(\left(f \cdot \pi\right) \cdot \left(\pi \cdot \pi\right)\right) \cdot \left(\frac{1}{2880} \cdot \left(f \cdot f\right)\right)\right) \cdot \left(-\frac{4}{\pi}\right)}\]
  4. Using strategy rm
  5. Applied add-sqr-sqrt2.7

    \[\leadsto \log \left((\frac{1}{12} \cdot \left(f \cdot \pi\right) + \left(\frac{\frac{4}{\pi}}{f}\right))_* - \left(\left(f \cdot \pi\right) \cdot \left(\pi \cdot \pi\right)\right) \cdot \left(\frac{1}{2880} \cdot \left(f \cdot f\right)\right)\right) \cdot \left(-\color{blue}{\sqrt{\frac{4}{\pi}} \cdot \sqrt{\frac{4}{\pi}}}\right)\]
  6. Applied distribute-lft-neg-in2.7

    \[\leadsto \log \left((\frac{1}{12} \cdot \left(f \cdot \pi\right) + \left(\frac{\frac{4}{\pi}}{f}\right))_* - \left(\left(f \cdot \pi\right) \cdot \left(\pi \cdot \pi\right)\right) \cdot \left(\frac{1}{2880} \cdot \left(f \cdot f\right)\right)\right) \cdot \color{blue}{\left(\left(-\sqrt{\frac{4}{\pi}}\right) \cdot \sqrt{\frac{4}{\pi}}\right)}\]
  7. Applied associate-*r*2.4

    \[\leadsto \color{blue}{\left(\log \left((\frac{1}{12} \cdot \left(f \cdot \pi\right) + \left(\frac{\frac{4}{\pi}}{f}\right))_* - \left(\left(f \cdot \pi\right) \cdot \left(\pi \cdot \pi\right)\right) \cdot \left(\frac{1}{2880} \cdot \left(f \cdot f\right)\right)\right) \cdot \left(-\sqrt{\frac{4}{\pi}}\right)\right) \cdot \sqrt{\frac{4}{\pi}}}\]

Runtime

Time bar (total: 3.2m)Debug logProfile

herbie shell --seed 2018206 +o rules:numerics
(FPCore (f)
  :name "VandenBroeck and Keller, Equation (20)"
  (- (* (/ 1 (/ PI 4)) (log (/ (+ (exp (* (/ PI 4) f)) (exp (- (* (/ PI 4) f)))) (- (exp (* (/ PI 4) f)) (exp (- (* (/ PI 4) f)))))))))