Simulation

• Time unit allows one to specify units for the time dimension for dimensional analysis. eg “year”, “s” etc.
• Controls aspect of the adaptive Runge-Kutta equation solver, which trade off performance and accuracy of the model.
• Note a first order explicit solver is the classic Jacobi method, which is the fastest, but least accurate solver.
• The algorithm is adaptive, so the step size will vary according to how stiff the system of equations is.
• Specifying a minimum step size prevents the system from stalling, at the expense of accuracy when the step size reaches that minimum.
• Specifying a maximum step size is useful to ensure one has sufficient data points for smooth plots.
• An iteration is the time between updates to plots, increasing the number of solver steps per iteration decreases the overhead involved in updating the display, at the expense of smoothness of the plots. Screen refresh is the period between screen updates, in ms. If an iteration takes less than this time, the screen refresh is postponed until the time has expired. 100ms is fast enough for a smooth animation of the simulation - increasing this value will improve simulation performance at the cost of a jerky animation of the simulation.
• Start time is the value of the system $t$ variable when the system is reset.
• Run until time can be used to pause the simulation ince t reaches a certain value. Setting this to “Infinity” causes the simulation to run indefinitely, or until some arithmetic error occurs.