Event Base

class pathsim.events._event.Event(func_evt=None, func_act=None, tolerance=0.0001)

Bases: object

This is the base class of the event handling system.

Monitors system state by evaluating an event function (func_evt) with scalar output.

func_evt(time) -> event?

If an event is detected, some action (func_act) is performed on the states of the blocks.

func_evt(time) == True -> event -> func_act(time)

The methods are structured such that event detection can be separated from event resolution. This is required for adaptive timestep solvers to approach the event and only resolve it when the event tolerance (‘tolerance’) is satisfied.

If no action function (func_act) is specified, the event will only be detected but other than that, no action will be triggered. For general state monitoring.

Parameters:

• func_evt (callable) – event function, where zeros are events

• func_act (callable) – action function for event resolution

• tolerance (float) – tolerance to check if detection is close to actual event

_history

history of event function evaluation after buffering

Type:

tuple[None, float], tuple[float, float], tuple[bool, float]

_times

tracking the event times

Type:

list[float]

_active

flag that sets event active or inactive

Type:

bool

on()

off()

reset()

Reset the recorded event times. Resetting the history is not required because of the ‘buffer’ method. Reactivates event tracking.

buffer(t)

Buffer the event function evaluation before the timestep is taken and the evaluation time.

Parameters:

t (float) – evaluation time for buffering history

estimate(t)

Estimate the time of the next event, based on history or internal schedule.

This improves simulation performance by estimating events before the simulation step such that fewer steps have to be rejected for event location.

Parameters:

t (float) – evaluation time for estimation

Returns:

estimated time until next event

Return type:

float | None

detect(t)

Evaluate the event function and decide if an event has occured. Can also use the history of the event function evaluation from before the timestep.

Notes

This does nothing and needs to be implemented for specific events!!!

Parameters:

t (float) – evaluation time for detection

Returns:

• detected (bool) – was an event detected?

• close (bool) – are we close to the event?

• ratio (float) – interpolated event location as ratio of timestep

resolve(t)

Resolve the event and record the time (t) at which it occurs.

Resolves event using the action function (func_act) if it is defined.

Otherwise this just marks the location of the event in time.

Parameters:

t (float) – evaluation time for event resolution