SUBROUTINE  initialisation(  u,  b,  p,  r,  u_exact, rnorm_k, &
                                   ip_xy,  ip_xz,  ip_yz,  voisin,  comm3d  )
      USE MPI
      USE numerics
      IMPLICIT  NONE
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)  ::  u
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)  ::  u_exact
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)  ::  b
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)  ::  p
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)  ::  r
      REAL(rp),  INTENT(OUT)  ::  rnorm_k
      INTEGER,   PARAMETER  ::  NB_VOISINS  =  6
      INTEGER,   DIMENSION(NB_VOISINS),  INTENT(IN)  ::  voisin
      INTEGER,   INTENT(IN)  ::  comm3d
      INTEGER,   INTENT(IN)  ::  ip_xy,  ip_xz,  ip_yz
      END  SUBROUTINE  initialisation