FUNCTION random_gauss( idum, upper_limit )

!------------------------------------------------------------------------------!
! Current revisions:
! -----------------
! 
!
! Former revisions:
! -----------------
! $Id: random_gauss.f90 484 2010-02-05 07:36:54Z fricke $
! RCS Log replace by Id keyword, revision history cleaned up
!
! Revision 1.4  2006/08/04 15:01:48  raasch
! Range of random number is limited by an upper limit (new second parameter)
!
! Revision 1.1  1998/03/25 20:09:47  raasch
! Initial revision
!
!
! Description:
! ------------
! Generates a gaussian distributed random number (mean value 1, sigma = 1)
! This routine is taken from the "numerical recipies".
!------------------------------------------------------------------------------!

    USE random_function_mod

    IMPLICIT NONE

    INTEGER :: idum, iset
    REAL    :: fac, gset, random_gauss, rsq, upper_limit, v1, v2

    SAVE  iset, gset

    DATA  iset /0/

!
!-- Random numbers are created as long as they do not fall below the given
!-- upper limit
    DO

       IF ( iset == 0 )  THEN
          rsq = 0.0
          DO  WHILE ( rsq >= 1.0  .OR.  rsq == 0.0 )
             v1  = 2.0 * random_function( idum ) - 1.0
             v2  = 2.0 * random_function( idum ) - 1.0
             rsq = v1**2 + v2**2
          ENDDO
          fac          = SQRT( -2.0 * LOG( rsq ) / rsq )
          gset         = v1 * fac
          random_gauss = v2 * fac + 1.0
          iset         = 1
       ELSE
          random_gauss = gset + 1.0
          iset         = 0
       ENDIF

       IF ( ABS( random_gauss - 1.0 ) <= upper_limit )  EXIT

    ENDDO

 END FUNCTION random_gauss