SUBROUTINE CREATE_DISCONTINUOUS_GRID ( XL, X_BEGIN, X_LENGTH, N)
c
c
C  WHAT              This routine will create a non-uniform computation grid
c                    of N zones  has a discontinuity in zone width at
c                    zone N/2.  The grid starts at location X_BEGIN and has
c                    total length X_LENGTH Thus the width of each zone
c                    a is X_LENGTH / N. Grid zones to the left of the
c                    discontinuity are half the size of zones to the right
c                    of the discontinuity.
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  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
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c
      REAL XL(1), X_BEGIN, X_LENGTH, DX_LEFT, DX_RIGHT, SINFAC, SINAMP
c
      DX_RIGHT = 4.0 * X_LENGTH / FLOAT(3*N)
      DX_LEFT = 2.0 * X_LENGTH / FLOAT(3*N)
      N_BREAK = N/2
c
      XL(1) = X_BEGIN
      DO I = 2,N_BREAK
         XL(I) = XL(I-1) + DX_LEFT
      ENDDO
c
      DO I = N_BREAK+1,N+1
         XL(I) = XL(I-1) + DX_RIGHT
      ENDDO
c
      RETURN
      END  ! SUBROUTINE CREATE_DISCONTINUOUS_GRID