R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\sin \left(\frac{\phi_1 - \phi_2}{2}\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\sin \left(\frac{\phi_1 - \phi_2}{2}\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)
\begin{array}{l}
t_0 := \frac{\lambda_1 - \lambda_2}{2}\\
t_1 := \sin t_0\\
t_2 := \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot t_1\\
t_3 := {\left(\sin \left(\frac{\phi_1}{2}\right) \cdot \cos \left(\frac{\phi_2}{2}\right) - \cos \left(\frac{\phi_1}{2}\right) \cdot \sin \left(\frac{\phi_2}{2}\right)\right)}^{2}\\
R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{t_3 + t_1 \cdot t_2}}{\sqrt{1 - \left(t_3 + t_2 \cdot \sqrt[3]{t_1 \cdot \left(0.5 - 0.5 \cdot \cos \left(2 \cdot t_0\right)\right)}\right)}}\right)
\end{array}
(FPCore (R lambda1 lambda2 phi1 phi2)
:precision binary64
(*
R
(*
2.0
(atan2
(sqrt
(+
(pow (sin (/ (- phi1 phi2) 2.0)) 2.0)
(*
(* (* (cos phi1) (cos phi2)) (sin (/ (- lambda1 lambda2) 2.0)))
(sin (/ (- lambda1 lambda2) 2.0)))))
(sqrt
(-
1.0
(+
(pow (sin (/ (- phi1 phi2) 2.0)) 2.0)
(*
(* (* (cos phi1) (cos phi2)) (sin (/ (- lambda1 lambda2) 2.0)))
(sin (/ (- lambda1 lambda2) 2.0))))))))))(FPCore (R lambda1 lambda2 phi1 phi2)
:precision binary64
(let* ((t_0 (/ (- lambda1 lambda2) 2.0))
(t_1 (sin t_0))
(t_2 (* (* (cos phi1) (cos phi2)) t_1))
(t_3
(pow
(-
(* (sin (/ phi1 2.0)) (cos (/ phi2 2.0)))
(* (cos (/ phi1 2.0)) (sin (/ phi2 2.0))))
2.0)))
(*
R
(*
2.0
(atan2
(sqrt (+ t_3 (* t_1 t_2)))
(sqrt
(-
1.0
(+ t_3 (* t_2 (cbrt (* t_1 (- 0.5 (* 0.5 (cos (* 2.0 t_0)))))))))))))))double code(double R, double lambda1, double lambda2, double phi1, double phi2) {
return R * (2.0 * atan2(sqrt(pow(sin((phi1 - phi2) / 2.0), 2.0) + (((cos(phi1) * cos(phi2)) * sin((lambda1 - lambda2) / 2.0)) * sin((lambda1 - lambda2) / 2.0))), sqrt(1.0 - (pow(sin((phi1 - phi2) / 2.0), 2.0) + (((cos(phi1) * cos(phi2)) * sin((lambda1 - lambda2) / 2.0)) * sin((lambda1 - lambda2) / 2.0))))));
}
double code(double R, double lambda1, double lambda2, double phi1, double phi2) {
double t_0 = (lambda1 - lambda2) / 2.0;
double t_1 = sin(t_0);
double t_2 = (cos(phi1) * cos(phi2)) * t_1;
double t_3 = pow(((sin(phi1 / 2.0) * cos(phi2 / 2.0)) - (cos(phi1 / 2.0) * sin(phi2 / 2.0))), 2.0);
return R * (2.0 * atan2(sqrt(t_3 + (t_1 * t_2)), sqrt(1.0 - (t_3 + (t_2 * cbrt(t_1 * (0.5 - (0.5 * cos(2.0 * t_0)))))))));
}



Bits error versus R



Bits error versus lambda1



Bits error versus lambda2



Bits error versus phi1



Bits error versus phi2
Results
Initial program 24.3
Applied div-sub_binary6424.3
Applied sin-diff_binary6423.8
Applied div-sub_binary6423.8
Applied sin-diff_binary6413.9
Applied add-cbrt-cube_binary6413.9
Applied sqr-sin-a_binary6413.9
Final simplification13.9
herbie shell --seed 2021329
(FPCore (R lambda1 lambda2 phi1 phi2)
:name "Distance on a great circle"
:precision binary64
(* R (* 2.0 (atan2 (sqrt (+ (pow (sin (/ (- phi1 phi2) 2.0)) 2.0) (* (* (* (cos phi1) (cos phi2)) (sin (/ (- lambda1 lambda2) 2.0))) (sin (/ (- lambda1 lambda2) 2.0))))) (sqrt (- 1.0 (+ (pow (sin (/ (- phi1 phi2) 2.0)) 2.0) (* (* (* (cos phi1) (cos phi2)) (sin (/ (- lambda1 lambda2) 2.0))) (sin (/ (- lambda1 lambda2) 2.0))))))))))