Average Error: 14.5 → 0.4
Time: 2.2m
Precision: 64
Internal Precision: 128
\[\left(\frac{\pi}{2} \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \left(\frac{1}{a} - \frac{1}{b}\right)\]
\[\left(\left(b - a\right) \cdot \frac{1}{\frac{\left(b + a\right) \cdot 2}{\pi}}\right) \cdot \frac{\frac{1}{b - a}}{a \cdot b}\]

Error

Bits error versus a

Bits error versus b

Derivation

  1. Initial program 14.5

    \[\left(\frac{\pi}{2} \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \left(\frac{1}{a} - \frac{1}{b}\right)\]
  2. Simplified14.5

    \[\leadsto \color{blue}{\frac{\frac{\pi}{b \cdot b - a \cdot a}}{\frac{2}{\frac{1}{a} - \frac{1}{b}}}}\]
  3. Using strategy rm
  4. Applied difference-of-squares9.7

    \[\leadsto \frac{\frac{\pi}{\color{blue}{\left(b + a\right) \cdot \left(b - a\right)}}}{\frac{2}{\frac{1}{a} - \frac{1}{b}}}\]
  5. Applied associate-/r*9.1

    \[\leadsto \frac{\color{blue}{\frac{\frac{\pi}{b + a}}{b - a}}}{\frac{2}{\frac{1}{a} - \frac{1}{b}}}\]
  6. Using strategy rm
  7. Applied frac-sub9.2

    \[\leadsto \frac{\frac{\frac{\pi}{b + a}}{b - a}}{\frac{2}{\color{blue}{\frac{1 \cdot b - a \cdot 1}{a \cdot b}}}}\]
  8. Applied associate-/r/9.1

    \[\leadsto \frac{\frac{\frac{\pi}{b + a}}{b - a}}{\color{blue}{\frac{2}{1 \cdot b - a \cdot 1} \cdot \left(a \cdot b\right)}}\]
  9. Applied div-inv9.1

    \[\leadsto \frac{\color{blue}{\frac{\pi}{b + a} \cdot \frac{1}{b - a}}}{\frac{2}{1 \cdot b - a \cdot 1} \cdot \left(a \cdot b\right)}\]
  10. Applied times-frac0.3

    \[\leadsto \color{blue}{\frac{\frac{\pi}{b + a}}{\frac{2}{1 \cdot b - a \cdot 1}} \cdot \frac{\frac{1}{b - a}}{a \cdot b}}\]
  11. Simplified0.3

    \[\leadsto \color{blue}{\left(\frac{\pi}{\left(b + a\right) \cdot 2} \cdot \left(b - a\right)\right)} \cdot \frac{\frac{1}{b - a}}{a \cdot b}\]
  12. Using strategy rm
  13. Applied clear-num0.4

    \[\leadsto \left(\color{blue}{\frac{1}{\frac{\left(b + a\right) \cdot 2}{\pi}}} \cdot \left(b - a\right)\right) \cdot \frac{\frac{1}{b - a}}{a \cdot b}\]
  14. Final simplification0.4

    \[\leadsto \left(\left(b - a\right) \cdot \frac{1}{\frac{\left(b + a\right) \cdot 2}{\pi}}\right) \cdot \frac{\frac{1}{b - a}}{a \cdot b}\]

Reproduce

herbie shell --seed 2019053 
(FPCore (a b)
  :name "NMSE Section 6.1 mentioned, B"
  (* (* (/ PI 2) (/ 1 (- (* b b) (* a a)))) (- (/ 1 a) (/ 1 b))))