real function rumach ()
C***BEGIN PROLOGUE  RUMACH
C***PURPOSE  Compute the unit roundoff of the machine.
C***CATEGORY  R1
C***TYPE      SINGLE PRECISION (RUMACH-S, DUMACH-D)
C***KEYWORDS  MACHINE CONSTANTS
C***AUTHOR  Hindmarsh, Alan C., (LLNL)
C***DESCRIPTION
C *Usage:
c        real  a, rumach
c        a = rumach()
C
C *Function Return Values:
c     a : the unit roundoff of the machine.
C
C *Description:
C     The unit roundoff is defined as the smallest positive machine
C     number u such that  1.0 + u .ne. 1.0.  This is computed by RUMACH
C     in a machine-independent manner.
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   930216  DATE WRITTEN
C   930818  Added SLATEC-format prologue.  (FNF)
C***END PROLOGUE  RUMACH
C
C*Internal Notes:
C-----------------------------------------------------------------------
C Subroutines/functions called by RUMACH.. None
C-----------------------------------------------------------------------
C**End
C
      real u, comp
c***first executable statement  rumach
      u = 1.0e0
 10   u = u*0.5e0
      comp = 1.0e0 + u
      if (comp .ne. 1.0e0) go to 10
      rumach = u*2.0e0
      return
c----------------------- end of function rumach ------------------------
      end