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subroutine rndblk(t,x,nx,z,nz,u,nu,rpar,nrpar,ipar,nipar,nclock,
& out,nout,flag)
double precision t,x(*),z(*),u(*),rpar(*),out(*)
double precision urand,sr,si,t1
integer ipar(*),flag
integer halt
common /coshlt/ halt
common /dbcos/ idb
c
c ipar(1)
c 0 : uniform
c 1 : normal
c rpar(1:nout)=mean
c rpar(nout+1:2*nout)=deviation
c rpar(2*nout+1)=dt
c
if(idb.eq.1) then
write(6,'(''rndblk t='',e10.3,'' flag='',i1)') t,flag
endif
c
if(flag.eq.1) then
do 10 i=1,nout
out(i)=rpar(i)+rpar(nout+i)*z(i+1)
10 continue
elseif(flag.eq.2.or.flag.eq.4) then
c uniform
if(ipar(1).eq.0) then
iy=int(z(1))
do 20 i=1,nz-1
z(i+1)=urand(iy)
20 continue
else
iy=int(z(1))
c normal
do 30 i=1,nz-1
75 sr=2.0d+0*urand(iy)-1.0d+0
si=2.0d+0*urand(iy)-1.0d+0
t1 = sr*sr+si*si
if (t1 .gt. 1.0d+0) go to 75
z(i+1) = sr*sqrt(-2.0d+0*log(t1)/t1)
30 continue
endif
z(1)=iy
elseif(flag.eq.3) then
out(1)=t+rpar(2*(nz-1)+1)
endif
return
end
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