The TaskList class implements methods to build and execute a set of tasks with associated dependencies. The main functionality of the class is implemented in two member functions:
AddTask is a templated variadic function that takes the task function to be executed, the task dependencies (see TaskID below), and the arguments to the task function as it's arguments. All arguments are captured by value in a lambda for later execution.
When adding functions that are non-static class member functions, a slightly different interface is required. The first argument should be the class-name-scoped name of the function. For example, for a function named DoSomething in class SomeClass, the first argument would be &SomeClass::DoSomething. The second argument should be a pointer to the object that should invoke this member function. Finally, the dependencies and function arguments should be provided as described above.
Examples of both AddTask calls can be found in the advection example here.
DoAvailable loops over the task list once, executing all tasks whose dependencies are satisfied. The function returns either TaskListStatus::complete if all tasks have been executed (and the task list is therefore empty) or TaskListStatus::running if tasks remain to be completed.
The TaskID class implements methods that allow Parthenon to keep track of tasks, their dependencies, and what remains to be completed. The main way application code will interact with this object is as a returned object from TaskList::AddTask and as an argument to subsequent calls to TaskList::AddTask as a dependency for other tasks. When used as a dependency, TaskID objects can be combined with the bitwise or operator (|) to specify multiple dependencies.