RKF21 (Fehlberg)

class pathsim.solvers.rkf21.RKF21(*solver_args, **solver_kwargs)

Bases: ExplicitRungeKutta

Three-stage, 2nd order Runge-Kutta-Fehlberg method with embedded 1st order error estimate.

Characteristics

• Order: 2 (propagating) / 1 (embedded)

• Stages: 3

• Explicit, adaptive timestep

Note

The cheapest adaptive explicit method available. The low order means the error estimate itself is coarse, so step-size control is less reliable than with higher-order pairs. Useful for rough exploratory runs of a new block diagram or when step size is dominated by discrete events (zero crossings, scheduled triggers) rather than truncation error. For production simulations, RKBS32 or RKDP54 are almost always preferable.

References

[1]

Fehlberg, E. (1969). “Low-order classical Runge-Kutta formulas with stepsize control and their application to some heat transfer problems”. NASA Technical Report TR R-315.

[2]

Hairer, E., Nørsett, S. P., & Wanner, G. (1993). “Solving Ordinary Differential Equations I: Nonstiff Problems”. Springer Series in Computational Mathematics, Vol. 8. :doi:`10.1007/978-3-540-78862-1`