The Fast Simulation of the CMS Experiment

The CMS collaboration has developed a fast Monte Carlo simulation of the CMS detector with event production rates ~ 100 times faster than the GEANT4-based simulation ('full simulation'), with nonetheless comparable accuracy for most of the physics objects typically considered in the analyses. We discuss basic technical principles of the CMS Fast Simulation and their implementation in the different components of the detector, and we illustrate the most recent developments towards a tighter integration with the full simulation and a better flexibility