for i, mpa, ndims, rv in zip(it.count(), mpas, mpas_ndims, rightvec):
        if ndims == 2:
            rightvec_out[i] = _eig_rightvec_add(rv, mpa.lt[pos], mps_lten)
        elif ndims == 1:
            rightvec_out[i] = _eig_rightvec_add_mps(rv, mpa.lt[pos], mps_lten)