C
C $Id: random.F,v 1.4 1998/07/16 16:40:25 jjv5 Exp arjan $
C
C------------------------------------------------------------------------
C     this file contains random number generators

CCC----------------------------------------------------------CCC

      FUNCTION xrandom(idum)
C
C     random number generator, taken from Numerical Recipes
C     returns a random between 0.0 and 1.0
C
      INTEGER idum,IA,IM,IQ,IR,NTAB,NDIV
      double precision xrandom,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 11 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
11      continue
        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
      xrandom=min(AM*iy,RNMX)
      return
      END
C  (C) Copr. 1986-92 Numerical Recipes Software +).

CCC------------------------------------------------------------CCC

      FUNCTION irandom(idum,imax)
C
C     random number generator, adapted from Numerical Recipes
C     returns a random between 1.0 and imax
C
      INTEGER irandom,idum,imax,IA,IM,IQ,IR,NTAB,NDIV
      double precision xr,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 11 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
11      continue
        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
      xr=min(AM*iy,RNMX)
      irandom=xr*imax+1
      return
      END

C     adapted from Numerical Recipes
C     (C) Copr. 1986-92 Numerical Recipes Software +).

CCC------------------------------------------------------------------CCC

      function grandom(idum, var)

C     generates a random number from a gaussian distribution
C     with zero mean and variance var

      implicit double precision(a-h,o-z)

      parameter (a1=3.949846138)
      parameter (a3=0.252408784)
      parameter (a5=0.076542912)
      parameter (a7=0.008355968)
      parameter (a9=0.029899776)

      sum = 0.0
      do i=1,12
         sum = sum + xrandom(idum)
      enddo
      sum = 0.25*(sum-6.0)
      sum2 = sum*sum
      x = ((((a9*sum2+a7)*sum2+a5)*sum2+a3)*sum2+a1)*sum
      grandom = x*var
      return
      end

CCC------------------------------------------------------------------CCC