In the classic Simulink® workflow, when you simulate a model, Simulink:
Compiles the model
Simulates the model
Terminates the simulation
While developing a model, you typically simulate a model repeatedly as you iterate the design. For example, you might calibrate input values or block parameters for a particular response. Changing these values or parameters does not always require compiling the model before simulating again. However, in the classic workflow, each simulation compiles the model, even if the changes do not alter the model structurally. Each compile slows down the process and increases overall simulation time.
Fast restart allows you to perform iterative simulations without compiling a model or terminating the simulation each time. Using fast restart, you compile a model only once. You can then tune parameters and root inputs and simulate the model again without spending time on compiling. Fast restart associates multiple simulation phases to a single compile phase to make iterative simulations more efficient.
Use fast restart when your workflow does not require structural changes to the model. Also, fast restart is better suited if the workflow involves any of these factors:
The model requires multiple simulations in which simulation inputs or parameters change in every iteration.
The compile time of the model is several seconds or longer.
You can use fast restart in normal and accelerator simulation modes. When you use fast restart in accelerator mode, you reduce simulation time and perform only a single compilation.