# Specifying and Configuring an ODE Solver (Control Design and Simulation Module)

For a given simulation, you specify and configure the ordinary differential equation (ODE) solver by using the Configure Simulation Parameters dialog box. Display this dialog box by double-clicking the Input Node of the Simulation Loop. This dialog box includes the **ODE Solver** pull-down menu, which you use to specify the ODE solver of a simulation.

Note If the term (variable) appears next to an ODE solver, that solver has a variable step size. The other ODE solvers have a fixed step size. |

## Configuring ODE Solver Options

If you specify a variable step-size ODE solver, you can configure the following options:

**Initial Step Size (s)****Minimum Step Size (s)****Maximum Step Size (s)****Relative Tolerance****Absolute Tolerance**

If you specify a fixed step-size ODE solver, you can configure only the **Step Size (s)** option.

Note If you are running a simulation on a real-time or embedded target, National Instruments recommends you specify a fixed step-size ODE solver. |