Average Error: 0.5 → 0.1
Time: 6.4s
Precision: binary64
\[\frac{1 - 5 \cdot \left(v \cdot v\right)}{\left(\left(\pi \cdot t\right) \cdot \sqrt{2 \cdot \left(1 - 3 \cdot \left(v \cdot v\right)\right)}\right) \cdot \left(1 - v \cdot v\right)} \]
↓
\[\frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\pi \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -6, 2\right)}}}{t}}{1 - v \cdot v} \]
\frac{1 - 5 \cdot \left(v \cdot v\right)}{\left(\left(\pi \cdot t\right) \cdot \sqrt{2 \cdot \left(1 - 3 \cdot \left(v \cdot v\right)\right)}\right) \cdot \left(1 - v \cdot v\right)}
↓
\frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\pi \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -6, 2\right)}}}{t}}{1 - v \cdot v}

(FPCore (v t)
 :precision binary64
 (/
  (- 1.0 (* 5.0 (* v v)))
  (* (* (* PI t) (sqrt (* 2.0 (- 1.0 (* 3.0 (* v v)))))) (- 1.0 (* v v)))))
↓
(FPCore (v t)
 :precision binary64
 (/
  (/ (/ (fma v (* v -5.0) 1.0) (* PI (sqrt (fma v (* v -6.0) 2.0)))) t)
  (- 1.0 (* v v))))
double code(double v, double t) {
	return (1.0 - (5.0 * (v * v))) / (((((double) M_PI) * t) * sqrt(2.0 * (1.0 - (3.0 * (v * v))))) * (1.0 - (v * v)));
}
↓
double code(double v, double t) {
	return ((fma(v, (v * -5.0), 1.0) / (((double) M_PI) * sqrt(fma(v, (v * -6.0), 2.0)))) / t) / (1.0 - (v * v));
}

Error

Bits error versus v

Bits error versus t

Derivation

  1. Initial program 0.5

    \[\frac{1 - 5 \cdot \left(v \cdot v\right)}{\left(\left(\pi \cdot t\right) \cdot \sqrt{2 \cdot \left(1 - 3 \cdot \left(v \cdot v\right)\right)}\right) \cdot \left(1 - v \cdot v\right)} \]

  2. Simplified0.5

    \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\sqrt{\mathsf{fma}\left(v, -6 \cdot v, 2\right)} \cdot \left(\left(\pi \cdot t\right) \cdot \left(1 - v \cdot v\right)\right)}} \]

  3. Applied associate-/r*_binary640.4

    \[\leadsto \color{blue}{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\sqrt{\mathsf{fma}\left(v, -6 \cdot v, 2\right)}}}{\left(\pi \cdot t\right) \cdot \left(1 - v \cdot v\right)}} \]

  4. Applied associate-/r*_binary640.4

    \[\leadsto \color{blue}{\frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\sqrt{\mathsf{fma}\left(v, -6 \cdot v, 2\right)}}}{\pi \cdot t}}{1 - v \cdot v}} \]

  5. Applied associate-/r*_binary640.1

    \[\leadsto \frac{\color{blue}{\frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\sqrt{\mathsf{fma}\left(v, -6 \cdot v, 2\right)}}}{\pi}}{t}}}{1 - v \cdot v} \]

  6. Applied associate-/l/_binary640.1

    \[\leadsto \frac{\frac{\color{blue}{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\pi \cdot \sqrt{\mathsf{fma}\left(v, -6 \cdot v, 2\right)}}}}{t}}{1 - v \cdot v} \]

  7. Simplified0.1

    \[\leadsto \frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\color{blue}{\pi \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -6, 2\right)}}}}{t}}{1 - v \cdot v} \]

  8. Final simplification0.1

    \[\leadsto \frac{\frac{\frac{\mathsf{fma}\left(v, v \cdot -5, 1\right)}{\pi \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -6, 2\right)}}}{t}}{1 - v \cdot v} \]

Reproduce

herbie shell --seed 2022095 
(FPCore (v t)
  :name "Falkner and Boettcher, Equation (20:1,3)"
  :precision binary64
  (/ (- 1.0 (* 5.0 (* v v))) (* (* (* PI t) (sqrt (* 2.0 (- 1.0 (* 3.0 (* v v)))))) (- 1.0 (* v v)))))