Modified version of DASSL for solving overdetermined systems of (singularily) implicit ODEs. The main difference to DASSL is in the corrector iteration part.

```
ODASSL ad-ons : FUEHRER, CLAUS
DEUTSCHE FORSCHUNGSANSTALT
FUER LUFT- UND RAUMFAHRT (DLR)
INST. DYNAMIC DER FLUGSYSTEME
D-8031 WESSLING (F.R.G)
```

Based on DASSL version dated to 900103 by:

```
DASSL-Author: PETZOLD, LINDA
APPLIED MATHEMATICS DIVISION 8331
SANDIA NATIONAL LABORATORIES
LIVERMORE, CA. 94550
```

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

Import the solver together with the correct problem:

```
from assimulo.solvers import ODASSL
from assimulo.problem import Overdetermined_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, y[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 = Overdetermined_Problem(res, y0, yd0, t0)
```

Note

For complex problems, it is recommended to check the available examples and the documentation in the problem class, `Overdetermined_Problem`

. It is also recommended to define your problem as a subclass of `Overdetermined_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 = ODASSL(mod)
```

Modify (optionally) the solver parameters.

Parameters:

`atol`

Defines the absolute tolerance(s) that is to be used by the solver.`backward`

Specifies if the simulation is done in reverse time.`clock_step`

Specifies if the elapsed time of an integrator step should be timed or not.`display_progress`

This option actives output during the integration in terms of that the current integration is periodically printed to the stdout.`inith`

This determines the initial step-size to be used in the integration.`maxh`

Defines the maximal step-size that is to be used by the solver.`maxord`

Defines the maximal order that is to be used by the solver.`maxsteps`

.`num_threads`

This options specifies the number of threads to be used for those solvers that supports it.`report_continuously`

This options specifies if the solver should report the solution continuously after steps.`rtol`

Defines the relative tolerance that is to be used by the solver.`safe`

.`store_event_points`

This options specifies if the solver should save additional points at the events, \(t_e^-, t_e^+\).`time_limit`

This option can be used to limit the time of an integration.`usejac`

This sets the option to use the user defined Jacobian.`verbosity`

This determines the level of the output.

Simulate the problem:

Information:

`ODASSL.get_options()`

Returns the current solver options.`ODASSL.get_supports()`

Returns the functionality which the solver supports.`ODASSL.get_statistics()`

Returns the run-time statistics (if any).`ODASSL.get_event_data()`

Returns the event information (if any).`ODASSL.print_event_data()`

Prints the event information (if any).`ODASSL.print_statistics()`

Prints the run-time statistics for the problem.