5 * Revision 1.1.1.1 1995/10/24 10:20:59 cernlib
9 #include "geant321/pilot.h"
10 *CMZ : 3.21/02 29/03/94 15.41.38 by S.Giani
12 SUBROUTINE POISSO(XAV,IRAN)
14 C *** GENERATION OF POISSON DISTRIBUTION ***
15 C *** NVE 16-MAR-1988 CERN GENEVA ***
18 C ORIGIN : H.FESEFELDT (27-OCT-1983)
20 C --- USE NORMAL DISTRIBUTION FOR <X> > 9.9 ---
33 IF(I.LE.5) RRR=XAV**I/NFAC(I)
34 C** STIRLING' S FORMULA FOR LARGE NUMBERS
35 IF(I.GT.5) RRR=EXP(I*LOG(XAV)-(I+0.5)*LOG(I*1.)+I-0.9189385)
40 C** NORMAL DISTRIBUTION WITH SIGMA**2 = <X>
42 RAN1=XAV+RAN1*SQRT(XAV)
46 C** FOR VERY SMALL XAV TRY IRAN=1,2,3