Below listed is the flow chart for the Pythia ntuples generation program.
* KI_PYT_MAIN * |-> KI_INIT Initialisations (FF, IO, HBOOK) * | |-> KI_DEF_KEYS * | | |-> KI_FFKEY2 * | |-> KI_FFGO * | |-> KI_CHECK_PARS * | |-> KI_NTPL_DEF Define HEPEVT ntuples * |-> KI_EVT_SEL Initialize event selection * |-> KI_PYT_INIT Pythia parameters initialization * |-> PYEVNT Pythia event generation (loop) * |-> KIU_FILL_HEPEVT Fill HEPEVT common * |-> |-> KIU_LUHEPC(1) * |-> KI_EVT_SEL Event selection * |-> KI_WR_EVT Write event * |-> KI_EVT_SEL Termination of selection * |-> PYSTAT Pythia generation statistics * |-> KI_END Termination
An important feature of the HEPEVT common used in CMSIM is that it is defined in single precision contrary to the convention in Pythia/Jetset conversion routine LUHEPC. This is achieved in CMKIN/CMSIM by calling CMKIN specific conversion routine KIU_LUHEPC instead of LUHEPC and defining the HEPEVT there in single precision. KIU_LUHEPC is essentially a copy of LUHEPC.