Average Error: 16.5 → 3.9
Time: 2.7m
Precision: 64
Internal Precision: 2176
\[\cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)\right) \cdot R\]
\[\log \left(e^{\cos^{-1} \left((e^{\log_* (1 + (\left(\cos \phi_2 \cdot \cos \phi_1\right) \cdot \left((\left(\cos \lambda_1\right) \cdot \left(\cos \lambda_2\right) + \left(\sin \lambda_2 \cdot \sin \lambda_1\right))_*\right) + \left(\sin \phi_2 \cdot \sin \phi_1\right))_*)} - 1)^*\right)}\right) \cdot R\]

Error

Bits error versus R

Bits error versus lambda1

Bits error versus lambda2

Bits error versus phi1

Bits error versus phi2

Derivation

  1. Initial program 16.5

    \[\cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)\right) \cdot R\]
  2. Using strategy rm
  3. Applied sub-neg16.5

    \[\leadsto \cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \cos \color{blue}{\left(\lambda_1 + \left(-\lambda_2\right)\right)}\right) \cdot R\]
  4. Applied cos-sum3.8

    \[\leadsto \cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \color{blue}{\left(\cos \lambda_1 \cdot \cos \left(-\lambda_2\right) - \sin \lambda_1 \cdot \sin \left(-\lambda_2\right)\right)}\right) \cdot R\]
  5. Applied simplify3.8

    \[\leadsto \cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \left(\color{blue}{\cos \lambda_1 \cdot \cos \lambda_2} - \sin \lambda_1 \cdot \sin \left(-\lambda_2\right)\right)\right) \cdot R\]
  6. Using strategy rm
  7. Applied add-log-exp3.8

    \[\leadsto \color{blue}{\log \left(e^{\cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \left(\cos \lambda_1 \cdot \cos \lambda_2 - \sin \lambda_1 \cdot \sin \left(-\lambda_2\right)\right)\right)}\right)} \cdot R\]
  8. Applied simplify3.8

    \[\leadsto \log \color{blue}{\left(e^{\cos^{-1} \left((\left(\cos \phi_2 \cdot \cos \phi_1\right) \cdot \left((\left(\cos \lambda_1\right) \cdot \left(\cos \lambda_2\right) + \left(\sin \lambda_2 \cdot \sin \lambda_1\right))_*\right) + \left(\sin \phi_2 \cdot \sin \phi_1\right))_*\right)}\right)} \cdot R\]
  9. Using strategy rm
  10. Applied expm1-log1p-u3.9

    \[\leadsto \log \left(e^{\cos^{-1} \color{blue}{\left((e^{\log_* (1 + (\left(\cos \phi_2 \cdot \cos \phi_1\right) \cdot \left((\left(\cos \lambda_1\right) \cdot \left(\cos \lambda_2\right) + \left(\sin \lambda_2 \cdot \sin \lambda_1\right))_*\right) + \left(\sin \phi_2 \cdot \sin \phi_1\right))_*)} - 1)^*\right)}}\right) \cdot R\]

Runtime

Time bar (total: 2.7m)Debug logProfile

herbie shell --seed '#(1064397287 3527694221 3797617954 1138343853 2854031332 1153838279)' +o rules:numerics
(FPCore (R lambda1 lambda2 phi1 phi2)
  :name "Spherical law of cosines"
  (* (acos (+ (* (sin phi1) (sin phi2)) (* (* (cos phi1) (cos phi2)) (cos (- lambda1 lambda2))))) R))