SUBROUTINE CREATE_NONUNIFORM_GRID ( XL, X_BEGIN, X_LENGTH, N)

c
C  WHAT              This routine will create a non-uniform computation grid
c                    of N zones beginning at location X_BEGIN and which has a
c                    total length X_LENGTH.
c
c                    The grid is defined by the locations of the lefthand
c                    zone interfaces XL.  Thus zone I would have its left
c                    edge at XL(I) and its right edge at XL(I+1).  Therefore
c                    a grid of N zones requires N+1 XL values.
c
c                    A sinusoid is used to vary the zone interface locations
c                    from those of a uniform grid of the same size and
c                    dimensions.
c
c  DIMENSIONS
c     output        It will be assumed that the dimension of the array XL
c                   is [1:N+1].
c
C  DATA
C    input         Input scalers are:
c                      X_BEGIN:  the starting value of the left edge of the
c                                grid.  That is XL(1) = X_BEGIN
c                      X_LENGTH: the total length of the grid.
c                                That is XL(N+1) = X_BEGIN + X_LENGTH
c                      N:        the number of zone in the grid.
C     output       Output arrays are:
c                      XL:       the locations of the lefthand zone interfaces
c
c
c
c
c
c

      REAL XL(1), X_BEGIN, X_LENGTH, DX, SINFAC, SINAMP

      SINFAC = 6.28318530717958 / FLOAT(N)
      SINAMP = 0.75

      DX = X_LENGTH / FLOAT(N)

      XL(1) = X_BEGIN
      DO I = 2,N+1
        XL(I) = XL(I-1) + DX * (1.0 + SINAMP * SIN(SINFAC * FLOAT(I-1)))
      ENDDO

      RETURN
      END  ! SUBROUTINE CREATE_NONUNIFORM_GRID