1 gaskelld 1.1 	real*8 function gauss1(nsigmax)
 2              
 3              **************************************************************************
 4              * This subroutine generates a random number distributed about a Gaussian
 5              * centered at zero with a standrd deviation of 1.  The gaussian is
 6              * truncated at nsigmax.  Use as a function like: VAL' = VAL + WIDTH*X
 7              *
 8              * Algorithm is from PHYSICS LETTERS B V.204, P.83 ''Review of particle
 9              * properties", Particle Data Group. (with nsigmax cutoff added).
10              **************************************************************************
11              
12              	implicit none
13              
14              	real*8 u1,u2,v1,v2,s,nsigmax
15              	real*8 grnd
16              
17              1	u1 = grnd()
18              	u2 = grnd()
19              	v1 = 2.0*u1-1.0
20              	v2 = 2.0*u2-1.0
21              	s  = v1**2+v2**2
22 gaskelld 1.1 
23              	if (s.gt.1. .or. s.eq.0) goto 1
24              
25              	gauss1 = v1*sqrt(-2.*log(s)/s)  ! <--want a natural log here
26              
27              	if (abs(gauss1).gt.nsigmax) goto 1	!truncate at nsigmax
28              
29              	return
30              	end