SUBROUTINE  pmv(  a,  b  )
      USE numerics
      IMPLICIT  NONE
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(OUT)   ::  a
      REAL(rp),  DIMENSION(sx-1:ex+1,sy-1:ey+1,sz-1:ez+1),  INTENT(IN)    ::  b
      END SUBROUTINE pmv