write_overlap_state Subroutine

    subroutine write_overlap_state(state, length, index)
        implicit none
        integer(n_int), intent(in) :: state(0:nIfTot, length)
        integer, intent(in) :: index, length
        integer :: nOccDets, i, ierr
        integer(n_int), allocatable :: buffer(:, :)
        real(dp) :: tmp_sign(lenof_sign)
        character(*), parameter :: this_routine = "write_overlap_state"

        ! check how many determinants are stored for this state on this core
        allocate(buffer(0:niftot, length), stat=ierr)
        nOccDets = 0
        do i = 1, length
            call extract_sign(state(:, i), tmp_sign)
            if (IsUnoccDet(tmp_sign)) then
                cycle
            end if
            nOccDets = nOccDets + 1
            buffer(:, nOccDets) = state(:, i)
        end do

        ! copy them to overlap_states
        if (allocated(overlap_states(index)%dets)) deallocate(overlap_states(index)%dets)
        allocate(overlap_states(index)%dets(0:nIfTot, nOccDets))
        overlap_states(index)%dets(:, 1:nOccDets) = buffer(:, 1:nOccDets)
        overlap_states(index)%nDets = nOccDets
        deallocate(buffer)
    end subroutine write_overlap_state