real function ran183(ix,iy,iz)
c
c     Algorithm AS 183 Appl. Statist. (1982) vol.31, no.2
c
c     Returns a pseudo-random number rectangularly distributed
c     between 0 and 1.   The cycle length is 6.95E+12 (See page 123
c     of Applied Statistics (1984) vol.33), not as claimed in the
c     original article.
c
c     IX, IY and IZ should be set to integer values between 1 and
c     30000 before the first entry.
c
c     Integer arithmetic up to 30323 is required.
c
      integer ix, iy, iz
c
      ix = 171 * mod(ix, 177) - 2 * (ix / 177)
      iy = 172 * mod(iy, 176) - 35 * (iy / 176)
      iz = 170 * mod(iz, 178) - 63 * (iz / 178)
c
      if (ix .lt. 0) ix = ix + 30269
      if (iy .lt. 0) iy = iy + 30307
      if (iz .lt. 0) iz = iz + 30323
c
c     If integer arithmetic up to 5212632 is available, the preceding
c     6 statements may be replaced by:
c
c     ix = mod(171 * ix, 30269)
c     iy = mod(172 * iy, 30307)
c     iz = mod(170 * iz, 30323)
c
      ran183 = mod(float(ix) / 30269. + float(iy) / 30307. +
     +                        float(iz) / 30323., 1.0)
      return
      end