What is MIL SIL ? Why do we compare MIL and SIL performance of a Simulink (MATLAB) Model?

Model-based development and verification approaches are highly desirable in the development of safety-critical embedded systems because they help to identify functional and non-functional issues in the early development stage, when verification complexity is relatively lower than that of the implemented systems.
Verification and validation is the backbone of any robust model-based development process. It can be used to check the accuracy of the models and algorithms based on code generated by test hardware and software interactions.
Test mechanisms adopted at Continental to test the model and software include:

• Model-in-the-loop (MIL) to verify the accuracy and acceptability using plant model of a control algorithm
• Software-in-the-loop (SIL) to validate the behavior of the generated C code used in the controller
• Processor-in-the-loop (PIL) to validate the referenced model by generating production code using the model reference target—this code is cross-compiled for and executed on a target processor or an equivalent instruction set simulator