SUBROUTINE MAT_VEC (imeta,jmeta,NLEV,X)

! ***********************************************
! *                                             *
! *     MATRIX-VECTOR MULTIPLICATION            * 
! *     y = P_inv * x   (P_inv is diagonal)     * 
! *                                             *
! ***********************************************
      INCLUDE 'mpif.h'
!-----------------------------------------------------------------------
      REAL,ALLOCATABLE ::  WPEN(:)
      REAL                 X(1:imeta,1:jmeta,1:NLEV)
!=================================================================
!---    read penalty weights (fine resolution in this case)

      ALLOCATE(WPEN(1:NLEV))

      IWPEN=53
      CLOSE(IWPEN)
      OPEN(IWPEN,file='wpen',status='unknown',form='unformatted')
      READ(IWPEN) WPEN
      CLOSE(IWPEN,STATUS='KEEP')

!!    write(*,*) "READ WPEN: min,max WPEN=",minval(WPEN),maxval(WPEN) 
!=================================================================
!---    MULTIPLICATION 

        DO L=1,NLEV
         if(WPEN(L).LT.1.E19) then
         sqrtwpen=sqrt(WPEN(L))
           X(:,:,L)=X(:,:,L)*sqrtwpen
         else
           X(:,:,L)=0.0
         end if
        ENDDO

      DEALLOCATE(WPEN)
!------------------------------------------------------------------
                            RETURN
                             END