  use module_vol
  implicit none

  SU3_FIELD     :: w
  SPINCOL_FIELD :: b, a
  COMPLEX       :: a1, a2, a3, a4
  integer       :: i, ca, cb

  ! statement function:
  
  COMPLEX :: i_times, c
  i_times(c) = cmplx(-aimag(c), real(c))

  !$omp parallel do private(ca, cb, a1, a2, a3, a4)
  do i = 1, volh
     do ca = 1, NCOL
