!      program main
!      implicit none
!      double precision gasdev2,x(2000),std1,fmean1,
!     &                 std2,fmean2,gasdev
!      integer idum,i,n
!      idum=-1
!      do i=5,2000
!        do n=1,i
!          x(n)=gasdev2()
!        enddo
!        call stdmean(i,x,std1,fmean1)
!        do n=1,i
!          x(n)=gasdev(idum)
!        enddo
!        call stdmean(i,x,std2,fmean2)
!        write(2,310)i,std1,fmean1,std2,fmean2
!      enddo
!310   format(1x,i8,4f15.10)
!      end
!
      double precision function gasdev2()
      implicit none   
!
! Return a normally distributed deviate with zero mean and unit variance,
! 
      integer iset
      double precision fac,gset,rsq,v1,v2,ran2
      save iset,gset
      data iset/0/

      if(iset.eq.0)then
1       v1=2.0d0*ran2()-1.0d0
        v2=2.0d0*ran2()-1.0d0
        rsq=v1*v1+v2*v2
        if(rsq.ge.1.0d0.or.rsq.eq.0.0d0)goto 1
        fac=dsqrt(-2.0d0*dlog(rsq)/rsq)
        gset=v1*fac
        gasdev2=v2*fac
        iset=1
      else
        gasdev2=gset
        iset=0
      endif
      return
      end

      double precision function gasdev(idum)
      implicit none
      integer idum
!
! Return a normally distributed deviate with zero mean and unit variance,
! using ran1(idum) as the source of uniform deviates
      integer iset
      double precision fac,gset,rsq,v1,v2,ran1
      save iset,gset
      data iset/0/
      if(idum.lt.0)iset=0
      if(iset.eq.0)then
1       v1=2.0d0*ran1(idum)-1.0d0
        v2=2.0d0*ran1(idum)-1.0d0
        rsq=v1*v1+v2*v2
        if(rsq.ge.1.0d0.or.rsq.eq.0.0d0)goto 1
        fac=dsqrt(-2.0d0*dlog(rsq)/rsq)
        gset=v1*fac
        gasdev=v2*fac
        iset=1
      else
        gasdev=gset
        iset=0
      endif
      return
      end
      
!      double precision function ran1(idum)
!      implicit none
!      integer idum,IA,IM,IQ,IR,NTAB,NDIV
!      double precision AM,EPS,RNMX
!      PARAMETER(IA=16807,IM=2147483647,AM=1.0d0/IM,IQ=127773,
!     &   IR=2836,NTAB=32,NDIV=1+(IM-1)/NTAB,EPS=1.2d-15,
!     &   RNMX=1.0d0-EPS)
!
! Minimal random number generator of Park and Miller with Bays-Durham shuffle and
! added safegaurds. Return a uniform random deviate between 0.0 and 1.0, exclusive
! of the endpoint values. Call with idum a negative integer to initilize; 
! thereafter, do not alter idum between successive deviates in a sequence. RNMX
! should approximate the largest floating value that is less than 1.
!
!      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
!        enddo
!        iy=iv(1)
!      endif
!      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=dmin1(AM*iy,RNMX)
!      return
!      end