Function dense_fallback

cpp_core/src/rmmdiis.cpp:202–237

}

MatFreeRmmDiisResult dense_fallback(
    const HamiltonianOp& h_op,
    int n_pw,
    int n_bands
) {
    std::vector<Complex> H(static_cast<std::size_t>(n_pw) * n_pw, Complex{0.0, 0.0});
    std::vector<Complex> e_j(static_cast<std::size_t>(n_pw), Complex{0.0, 0.0});
    std::vector<Complex> h_col(static_cast<std::size_t>(n_pw), Complex{0.0, 0.0});
    for (int j = 0; j < n_pw; ++j) {
        std::fill(e_j.begin(), e_j.end(), Complex{0.0, 0.0});
        e_j[static_cast<std::size_t>(j)] = Complex{1.0, 0.0};
        h_op(e_j.data(), h_col.data(), n_pw, 1);
        for (int i = 0; i < n_pw; ++i) {
            H[static_cast<std::size_t>(i + n_pw * j)] = h_col[static_cast<std::size_t>(i)];
        }
    }
    const auto eig = diagonalize_hermitian_dense(H, n_pw);

    MatFreeRmmDiisResult out;
    out.n_pw = n_pw;
    out.n_bands = n_bands;
    out.converged = true;
    out.iterations = 0;
    out.n_matvec = n_pw;
    out.max_residual_norm = 0.0;
    out.method = "dense_fallback";
    out.eigenvalues_ha.assign(eig.eigenvalues_ha.begin(), eig.eigenvalues_ha.begin() + n_bands);
    out.eigenvectors_col_major.resize(static_cast<std::size_t>(n_pw) * n_bands);
    for (int j = 0; j < n_bands; ++j) {
        for (int i = 0; i < n_pw; ++i) {
            out.eigenvectors_col_major[static_cast<std::size_t>(i + n_pw * j)] =
                eig.eigenvectors_col_major[static_cast<std::size_t>(i + n_pw * j)];
        }
    }
    return out;
}

} // namespace