This example introduces Tempus::TimeStepControl, which manages timestep-size selection independently of the stepper and application time loop. The van der Pol model is still provided through a Thyra::ModelEvaluator, the Forward Euler step is still performed by Tempus::StepperForwardEuler, and the application still manages the overall time loop and Tempus::SolutionHistory. However, timestep-size selection is now delegated to a Tempus::TimeStepControl object rather than being hardcoded directly in the application.

The main purpose of this step is to separate timestep-selection policy from both the stepping algorithm and the surrounding application logic. It should be noted that a Tempus::Stepper may suggest a future timestep size, but the final timestep-size selection occurs in Tempus::TimeStepControl.

Relative to Example 5: Introduce Stepper:

timestep control is moved into Tempus::TimeStepControl
the application initializes a dedicated timestep-control object
the time loop uses the control object to determine whether the current time and step index remain in range
timestep metadata for each new working state is assigned through the control object rather than directly in the application
the stepper and solution-history logic remain essentially unchanged

The central idea behind Tempus::TimeStepControl is that timestep size should be managed by a dedicated object that can enforce integration limits, policies, and strategies independently of the stepper itself.

This example uses only part of the full Tempus::TimeStepControl capability:

setting the final integration time
setting the number of time steps for constant-timestep control
using the control object to determine timestep metadata for each step
using the control object to test whether time and step index remain in range

The example continues to print the evolving solution in a simple table with columns for step index, time, , and . As in the previous examples, overall tutorial success should require both a successful integration status and a passing regression comparison of the final solution.

Transition notes: See Transition from Example 5 to Example 6 for a detailed explanation of what changed from Example 5: Introduce Stepper.

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