ran1.f90

产生服从N(0,1)分布的子程序（fortran）

	
!     +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
!                        产 生(0,1) 均匀分布随机数子程序
!     +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
	  function ran1(idum)	
	  integer idum,ia,im,iq,ir,ntab,ndiv
 	  real ran1,am,eps,rnmx
	  parameter(ia=16807,im=2147483647,am=1./im,iq=127773,ir=2836,&
	            ntab=32,ndiv=1+(im-1)/ntab,eps=1.2e-7,rnmx=1.-eps)
	  integer j,k,iv(ntab),iy
	  save iv,iy
	  data iv/ntab*0/,iy/0/
	  if (idum.le.0.or.iy.eq.0) then
	      idum=max(-idum,1)
		  do j=ntab+8,1,-1
	         k=idum/iq
		     idum=ia*(idum-k*iq)-ir*k
		     if (idum.lt.0) idum=idum+im
		     if (j.le.ntab) iv(j)=idum
		  end do
		  iy=iv(1)
	  end if
	  k=idum/iq
  	  idum=ia*(idum-k*iq)-ir*k
	  if (idum.lt.0) idum=idum+im
	  j=1+iy/ndiv
	  iy=iv(j)
	  iv(j)=idum
	  ran1=min(am*iy,rnmx)
	  end
!     -----------------------------------------------------------------------