  PARSIFAL (PARametrized SImulation by Farinelli And Lavezzi) is a fast and
reliable software tool that reproduces the complete response of a triple-GEM
detector to the passage of a charged particle, taking into account the main
physical effects. Starting from the detector configuration and the particle
information, PARSIFAL reproduces ionization, spatial and temporal diffusion,
effect of magnetic field, if present, and GEM amplification to provide the
dependable triple-GEM detector response. In the design and optimization stages
of this kind of detectors, simulations play an important role. Accurate and
robust software programs, such as GARFIELD++, can simulate the transport of
electrons and ions in a gas medium and their interaction with the electric
field, but they are CPU-time consuming. The necessity to reduce the processing
time while maintaining the precision of a full simulation is the main driver of
this work. For a given set of geometrical and electrical settings, GARFIELD++
is run once-and-for-all to provide the input parameters for PARSIFAL. Once
PARSIFAL is initialized and run, it produces the detector output, including the
signal induction and the output of the electronics. The results of the analysis
of the simulated data obtained with PARSIFAL are compared with the results of
the experimental data collected during a testbeam: some tuning factors are
applied to the simulation to improve the agreement. This paper describes the
structure of the code and the methodology used to match the output to the
experimental data.
