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fennecslite/dependencies/random/randother.f
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randother.f
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* Version 1.1 of random number routines
* Author: Charles Karney <karney@princeton.edu>
* Date: 1999-08-06 14:18:03 -0400
*
subroutine random_gauss(y,n,p,r)
implicit none
integer p
DOUBLE PRECISION r(0:100-1)
integer n
DOUBLE PRECISION y(0:n-1)
integer i
DOUBLE PRECISION pi,theta,z
DOUBLE PRECISION random
external random_array,random
data pi/3.14159265358979323846264338328d0/
REAL ys(0:n-1)
REAL spi,stheta,sz
REAL srandom
external srandom_array,srandom
data spi/3.14159265358979323846264338328/
if(n.LE.0)return
call random_array(y,n,p,r(0))
do i=0,int(n/2)*2-1,2
theta=pi*(2.0d0*y(i)-1.0d0)
z=sqrt(-2.0d0*log(y(i+1)))
y(i)=z*cos(theta)
y(i+1)=z*sin(theta)
end do
if(mod(n,2).EQ.0)return
theta=pi*(2.0d0*y(n-1)-1.0d0)
z=sqrt(-2.0d0*log(random(p,r(0))))
y(n-1)=z*cos(theta)
return
entry srandom_gauss(ys,n,p,r)
if(n.LE.0)return
call srandom_array(ys,n,p,r(0))
do i=0,int(n/2)*2-1,2
stheta=spi*(2.0*ys(i)-1.0)
sz=sqrt(-2.0*log(ys(i+1)))
ys(i)=sz*cos(stheta)
ys(i+1)=sz*sin(stheta)
end do
if(mod(n,2).EQ.0)return
stheta=spi*(2.0*ys(n-1)-1.0)
sz=sqrt(-2.0*srandom(p,r(0)))
ys(n-1)=sz*cos(stheta)
return
end
*
subroutine random_isodist(v,n,p,r)
implicit none
integer p
DOUBLE PRECISION r(0:100-1)
integer n
DOUBLE PRECISION v(0:3*n-1)
integer i
DOUBLE PRECISION pi,costheta,phi
external random_array
data pi/3.14159265358979323846264338328d0/
REAL vs(0:3*n-1)
REAL spi,scostheta,sphi
external srandom_array
data spi/3.14159265358979323846264338328/
if(n.LE.0)return
call random_array(v(n),2*n,p,r(0))
do i=0,n-1
costheta=2.0d0*v(n+2*i)-1.0d0
phi=pi*(2.0d0*v(n+2*i+1)-1.0d0)
v(3*i)=cos(phi)*sqrt(1.0d0-costheta**2)
v(3*i+1)=sin(phi)*sqrt(1.0d0-costheta**2)
v(3*i+2)=costheta
end do
return
entry srandom_isodist(vs,n,p,r)
if(n.LE.0)return
call srandom_array(vs(n),2*n,p,r(0))
do i=0,n-1
scostheta=2.0*vs(n+2*i)-1.0
sphi=spi*(2.0*vs(n+2*i+1)-1.0)
vs(3*i)=cos(sphi)*sqrt(1.0-scostheta**2)
vs(3*i+1)=sin(sphi)*sqrt(1.0-scostheta**2)
vs(3*i+2)=scostheta
end do
return
end
*
subroutine random_cosdist(v,n,p,r)
implicit none
integer p
DOUBLE PRECISION r(0:100-1)
integer n
DOUBLE PRECISION v(0:3*n-1)
integer i
DOUBLE PRECISION pi,costheta2,phi
external random_array
data pi/3.14159265358979323846264338328d0/
REAL vs(0:2*n-1)
REAL spi,scostheta2,sphi
external srandom_array
data spi/3.14159265358979323846264338328/
if(n.LE.0)return
call random_array(v(n),2*n,p,r(0))
do i=0,n-1
costheta2=v(n+2*i)
phi=pi*(2.0d0*v(n+2*i+1)-1.0d0)
v(3*i)=cos(phi)*sqrt(1.0d0-costheta2)
v(3*i+1)=sin(phi)*sqrt(1.0d0-costheta2)
v(3*i+2)=sqrt(costheta2)
end do
return
entry srandom_cosdist(vs,n,p,r)
if(n.LE.0)return
call srandom_array(vs(n),2*n,p,r(0))
do i=0,n-1
scostheta2=vs(n+2*i)
sphi=spi*(2.0*vs(n+2*i+1)-1.0)
vs(3*i)=cos(sphi)*sqrt(1.0-scostheta2)
vs(3*i+1)=sin(sphi)*sqrt(1.0-scostheta2)
vs(3*i+2)=sqrt(scostheta2)
end do
return
end
*
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