!
  !----------------------------------------------------------------
  subroutine green_linsys ( vr, g2kin, xxk, nw, w, green, igstart, igstop)
  !----------------------------------------------------------------
  ! 
  use parameters
  use constants
  use gspace
  use kspace
!#ifdef __PARA
!  USE para
!  USE mp_global,  ONLY : nproc, mpime, nproc_pool, my_pool_id, me_pool
!  USE mp, ONLY:  mp_barrier
!#endif
  implicit none
  !
  real(dbl) :: xxk(3)
  integer :: ig, igp, nw
  integer :: igstart, igstop
  integer :: ig1, ig2, idummy, iw, ierr, ibnd, ios, recl, unf_recl, ikf, fold(nq)
  real(dbl) :: x, delta, kplusg(3), g2kin(ngm), eval(nbnd_occ)
  real(dbl) :: eval_all(nbnd), w(nw), w_ryd(nw)
  complex(dbl) :: vr(nr), gr(ngm), cw
  complex(dbl) :: psi_all(ngm,nbnd)
  complex(dbl) :: green(nrs,nrs,nw)
  complex(kind=DP) ::  ost(ngms,ngms,nbnd), cf(nw,nbnd)

  call start_clock('green_linsys')

  w_ryd = w/ryd2ev

  ! the k-dependent kinetic energy in Ry
  !
  do ig = 1, ngm
    kplusg = xxk + g(:,ig)
    g2kin ( ig ) = tpiba2 * dot_product ( kplusg, kplusg )
  enddo
  !
  call  eigenstates_all ( vr, g2kin, psi_all, eval_all )
  !
  do ibnd = 1, nbnd
    if (ibnd.le.nbnd_occ) then
      delta =  1.d0
    else
      delta = -1.d0
    endif
    do iw = 1, nw
       ! 2 is for the spin
       cf(iw,ibnd) = 2.d0 / ( w_ryd(iw) - eval_all(ibnd) - ci * delta * eta)
    enddo
  enddo
  do ig = igstart, igstop
    do igp = 1, ngms
      do ibnd = 1, nbnd
         ost(ig,igp,ibnd) = psi_all(ig,ibnd)*conjg(psi_all(igp,ibnd)) 
      enddo
    enddo
  enddo
  !
  !  loop on bare perturbations ig and fixed k point
  !
  green = czero
  do iw = 1, nw
    do igp = 1, ngms
      do ig = igstart, igstop 
        do ibnd = 1, nbnd
           green (ig,igp,iw) = green (ig,igp,iw) + ost(ig,igp,ibnd) * cf(iw,ibnd)
        enddo
      enddo
    enddo
  enddo
  !
!  do ig = igstart, igstop
!    do igp = 1, ngms
!      do iw = 1, nw
!        write(100,*) w(iw), real(green (ig,igp,iw)),aimag(green (ig,igp,iw))
!      enddo
!    enddo
!  enddo
  !
  call stop_clock('green_linsys')
  ! 
  return
  end subroutine green_linsys
  !----------------------------------------------------------------
  !