# RK5Integrator¶

class gala.integrate.RK5Integrator(func, func_args=(), func_units=None)[source]

Bases: gala.integrate.core.Integrator

Initialize a 5th order Runge-Kutta integrator given a function for computing derivatives with respect to the independent variables. The function should, at minimum, take the independent variable as the first argument, and the coordinates as a single vector as the second argument. For notation and variable names, we assume this independent variable is time, t, and the coordinate vector is named x, though it could contain a mixture of coordinates and momenta for solving Hamilton’s equations, for example.

Parameters: func : func A callable object that computes the phase-space coordinate derivatives with respect to the independent variable at a point in phase space. func_args : tuple (optional) Any extra arguments for the function. func_units : UnitSystem (optional) If using units, this is the unit system assumed by the integrand function.

Methods Summary

 run(w0[, mmap]) Run the integrator starting from the specified phase-space position. step(t, w, dt) Step forward the vector w by the given timestep.

Methods Documentation

run(w0, mmap=None, **time_spec)[source]

Run the integrator starting from the specified phase-space position. The initial conditions w0 should be a PhaseSpacePosition instance.

There are a few combinations of keyword arguments accepted for specifying the timestepping. For example, you can specify a fixed timestep (dt) and a number of steps (n_steps), or an array of times:

dt, n_steps[, t1] : (numeric, int[, numeric])
A fixed timestep dt and a number of steps to run for.
dt, t1, t2 : (numeric, numeric, numeric)
A fixed timestep dt, an initial time, and a final time.
t : array_like
An array of times to solve on.


Warning

Right now, this always returns a Orbit instance. This is wrong and will change!

Todo

Allow specifying the return orbit class.

Parameters: w0 : PhaseSpacePosition Initial conditions. **time_spec Timestep information passed to parse_time_specification. orbit : Orbit
step(t, w, dt)[source]

Step forward the vector w by the given timestep.

Parameters: dt : numeric The timestep to move forward.