1. A computer-implemented method of creating a simulation engine for simulating a circuit design, the method comprising: receiving a source code contribution from a high level modeling system; receiving a simulation model specified in an interpretive language that specifies the circuit design; compiling the source code contribution together with the simulation model using a Just-In-Time compiler; and responsive to the compiling, outputting a simulation engine in native machine code format as a single, integrated software component formed from the source code contribution and the simulation model.