anchor.diff:    END_DOC
     integer                        :: k
   
  +  !$OMP PARALLEL DO DEFAULT(SHARED) PRIVATE(k)
     do k=1,N_det
       psi_bilinear_matrix_order_transp_reverse(psi_bilinear_matrix_transp_order(k)) = k
     enddo
  +  !$OMP END PARALLEL DO
   END_PROVIDER
   
   
  
positive.code: 
    n_singles = 1
    !DIR$ VECTOR ALIGNED
    do i=0,size_buffer-block_size, block_size
  
      do k=1,Nint
        do ii=1,block_size
          xorvec(ii, k) = xor( spindet(k), buffer(k,ii+i) )
        enddo
      enddo
      
      do ii=1,block_size
        if (xorvec(ii,1) /= 0_8) then
          degree(ii) = popcnt(xorvec(ii,1))
        else
          degree(ii) = 0
        endif
  
        do k=2,Nint
          if ( (degree(ii) <= 2).and.(xorvec(ii,k) /= 0_8) ) then
            degree(ii) = degree(ii) + popcnt(xorvec(ii,k))
          endif
        enddo
      enddo
  
      do ii=1,block_size
        if ( degree(ii) == 2 ) then
          singles(n_singles) = idx(i+ii)
          n_singles = n_singles+1
        endif
      enddo
  
    enddo
  
    imax = size_buffer-i
  
    do k=1,Nint
      do ii=1,imax
        xorvec(ii, k) = xor( spindet(k), buffer(k,ii+i) )
      enddo
    enddo
    
    do ii=1,imax
      if (xorvec(ii,1) /= 0_8) then
        degree(ii) = popcnt(xorvec(ii,1))
      else
        degree(ii) = 0
      endif
  
      do k=2,Nint
        if ( (degree(ii) <= 2).and.(xorvec(ii,k) /= 0_8) ) then
          degree(ii) = degree(ii) + popcnt(xorvec(ii,k))
        endif
      enddo
    enddo
  
    do ii=1,imax
      if ( degree(ii) == 2 ) then
        singles(n_singles) = idx(i+ii)
        n_singles = n_singles+1
      endif
    enddo
    n_singles = n_singles-1
    
  
negative.code:     to_sort(k) = int(N_det_alpha_unique,8) * int(j-1,8) + int(i,8)
      psi_bilinear_matrix_order(k) = k
    enddo
    !$OMP END PARALLEL DO
    call i8sort(to_sort, psi_bilinear_matrix_order, N_det)
    call iset_order(psi_bilinear_matrix_rows,psi_bilinear_matrix_order,N_det)
    call iset_order(psi_bilinear_matrix_columns,psi_bilinear_matrix_order,N_det)
  