The Task class defined in C++ provides the base implementation for tasks, which are simple events that execute periodically or as scheduled. Derived classes should implement specific functionality within the start and execute functions. This guide provides an overview of how to interact with the Task class and its derived classes: Model, Monitor, and Event.

The Task Class

Description and Naming

The Task class defines a base task with parameters, inputs, and outputs. Derived classes should implement the start and execute functions to define specific task behavior. The Task class should not be used on its own.

For a complete guide on interacting with the Task and Model classes, refer to the Doxygen documentation: Task Doxygen Model Doxygen

Models vs. Tasks

Note that the Model class can do everything that a task can do. Model vs. Task really indicates intent — is the object a model? Or is it a software task? All of the task documentation here applies equally to model.

The only noteworthy code difference between models and tasks is that models are designed for simulation, and work with the simulation executive (rather than a generic executive, as is the case with Task). This means models have access to powerful features offered only by the simulation executive, but should not be used for any embedded applications.

Activation and Deactivation

Models and Tasks can (and should) be deactivated when they are not being used. Each is provided a default deactivate function which may be overridden.

Debugging

Models and Tasks may be set to a specific logging level independent of the simulation by setting the log level.

C++

task.logLevel(DEBUG);   // Valid choices are DEBUG, INFO, WARNING, ERROR, NONE -- default is WARNING

Python

task.logLevel(DEBUG)    # Valid choices are DEBUG, INFO, WARNING, ERROR, NONE -- default is WARNING

A Note on Scheduling

Tasks are created as standalone objects, but can be integrated or "scheduled" by the simulation executive. This is how they are typically handled, although special circumstances may require that they are not.

The simulation posesses three steps which are executed every time the simulation steps forward in time:

  • START_STEP, which runs a single time at the beginning of the sim step

  • DERIVATIVE, which runs every time derivatives are calculated in the integrator (once per step for Forward Euler integration, four times for RK4)

  • END_STEP, which runs a single time at the end of the sim step.

When tasks and models are created and made a child of the simulation executive, they are by default scheduled to run at all the above. However, they may be scheduled to run at one of the following options:

  • NOT_SCHEDULED Run only manually when called within another model or individually

  • STARTUP_ONLY Run only on simulation startup (the task start step) and not afterwards unless called within another model or individually

  • ALL Run every simulation step

  • START_STEP, run a single time at the beginning of the sim step

  • DERIVATIVE, run every time derivatives are calculated in the integrator (once per step for Forward Euler integration, four times for RK4)

  • END_STEP, run a single time at the end of the sim step.

Creating a Task

Description C++ Example Python Example

Default Constructor - Creates a default Task object which is not scheduled and has no parent. Default name.

 
Task task();
 
task = Task()

Executive Constructor - Creates a default Task object with parent as the simulation executive and scheduled to run on end step. Default name.

 
Task task(exc, END_STEP);
 
task = Task(exc, END_STEP)

Child Constructor - Creates a default Task object with parent as anbother task and scheduled to run only on startup. Default name.

 
Task task(parent, STARTUP_ONLY);
 
task = Task(parent, STARTUP_ONLY)

Constructor with Parent Task - Creates a default Task object with parent as anbother task and scheduled to run on derivative. Named "task"

 
Task task(parent, DERIVATIVE, "task");
 
task = Task(parent, DERIVATIVE, "task")

Running a Task

Description C++ Example Python Example

Starting Up a Task - Performs startup activities for the task.

 
int result = task.startup();
 
# Python example not available

Running a Task - Runs the task periodically.

 
result = task.run();
 
# Python example not available

Activating and Deactivating a Task

Description C++ Example Python Example

Activating a Task - Activates the task.

 
result = task.activate();
 
# Python example not available

Deactivating a Task - Deactivates the task.

 
result = task.deactivate();
 
# Python example not available

The Model Class

The Model class is a derived class of Task designed around the "black box" design of models. It should be implemented in derived classes via class inheritance.

Creating a Model

Description C++ Example Python Example

Default Constructor - Creates a default Model object.

 
Model model;
 
# Python example not available

Constructor with Parent Task - Creates a Model object with a specified parent task and schedule slot.

 
Task parentTask;
Model model(parentTask, 0, "ModelName");
 
# Python example not available

Constructor with Executive - Creates a Model object with a specified executive and schedule slot.

 
Executive exec;
Model model(exec, 0, "ModelName");
 
# Python example not available

The Monitor Class

The Monitor class is a simplified model that checks one or multiple conditions and sets a flag when triggered. It should be implemented in derived classes to define specific monitoring behavior.

Creating a Monitor

Description C++ Example Python Example

Default Constructor - Creates a default Monitor object.

 
Monitor monitor;
 
# Python example not available

Constructor with Parent Task - Creates a Monitor object with a specified parent task and schedule slot.

 
Task parentTask;
Monitor monitor(parentTask, 0, "MonitorName");
 
# Python example not available

Constructor with Executive - Creates a Monitor object with a specified executive and schedule slot.

 
Executive exec;
Monitor monitor(exec, 0, "MonitorName");
 
# Python example not available

Running a Monitor

Description C++ Example Python Example

Running a Monitor - Runs the monitor and checks conditions.

 
int result = monitor.run();
 
# Python example not available

Resetting a Monitor - Resets the monitor’s trigger to false.

 
monitor.reset();
 
# Python example not available

The Event Class

The Event class is designed to run only when triggered by an external flag, typically tied to the Monitor class. Derived classes should implement specific event behavior.

Creating an Event

Description C++ Example Python Example

Default Constructor - Creates a default Event object.

 
Event event;
 
# Python example not available

Constructor with Parent Task - Creates an Event object with a specified parent task and schedule slot.

 
Task parentTask;
Event event(parentTask, 0, "EventName");
 
# Python example not available

Constructor with Executive - Creates an Event object with a specified executive and schedule slot.

 
Executive exec;
Event event(exec, 0, "EventName");
 
# Python example not available

Running an Event

Description C++ Example Python Example

Running an Event - Runs the event when triggered.

 
int result = event.run();
 
# Python example not available