Radau IIA fifth-order three-stages with step-size control and continuous output. Based on the FORTRAN code RADAU5 by E.Hairer and G.Wanner, which can be found here: http://www.unige.ch/~hairer/software.html

Details about the implementation (FORTRAN) can be found in the book,:

Solving Ordinary Differential Equations II,
Stiff and Differential-Algebraic Problems

Authors: E. Hairer and G. Wanner
Springer-Verlag, ISBN: 3-540-60452-9


## Support¶

• State events (root funtions) : True
• Step events (completed step) : True
• Time events : True

## Usage¶

Import the solver together with the correct problem:

from assimulo.solvers import Radau5DAE
from assimulo.problem import Implicit_Problem


Define the problem, such as:

def res(t, y, yd): #Note that y and yd are 1-D numpy arrays.
res = yd[0]-1.0
return N.array([res]) #Note that the return must be numpy array, NOT a scalar.

y0  = [1.0]
yd0 = [1.0]
t0  = 1.0


Create a problem instance:

mod = Implicit_Problem(res, y0, yd0, t0)


Note

For complex problems, it is recommended to check the available examples and the documentation in the problem class, Implicit_Problem. It is also recommended to define your problem as a subclass of Implicit_Problem.

Warning

When subclassing from a problem class, the function for calculating the right-hand-side (for ODEs) must be named rhs and in the case with a residual function (for DAEs) it must be named res.

Create a solver instance:

sim = Radau5DAE(mod)


Modify (optionally) the solver parameters.

Parameters:

Methods:

• Radau5DAE.interpolate

Simulate the problem:

Information: