Function should_stop_vasp_like

cpp_core/src/davidson.cpp:630–694

};

bool should_stop_vasp_like(
    const std::vector<double>& current_ritz_values_ha,
    int n_bands,
    const MatFreeDavidsonOptions& opts,
    EigenvalueBreakState* state,
    double* max_eigenvalue_change_ha_out
) {
    if (max_eigenvalue_change_ha_out != nullptr) {
        *max_eigenvalue_change_ha_out = 0.0;
    }
    if (!opts.use_vasp_like_stop || state == nullptr || n_bands <= 0) {
        return false;
    }

    if (!state->have_previous) {
        state->previous_ritz_values_ha.assign(
            current_ritz_values_ha.begin(),
            current_ritz_values_ha.begin() + n_bands
        );
        state->have_previous = true;
        return false;
    }

    std::vector<double> deltas_ha(static_cast<std::size_t>(n_bands), 0.0);
    double max_delta_ha = 0.0;
    for (int j = 0; j < n_bands; ++j) {
        const double delta_ha = std::abs(
            current_ritz_values_ha[static_cast<std::size_t>(j)]
            - state->previous_ritz_values_ha[static_cast<std::size_t>(j)]
        );
        deltas_ha[static_cast<std::size_t>(j)] = delta_ha;
        max_delta_ha = std::max(max_delta_ha, delta_ha);
    }
    if (max_eigenvalue_change_ha_out != nullptr) {
        *max_eigenvalue_change_ha_out = max_delta_ha;
    }

    if (!state->have_first_step_delta) {
        state->first_step_delta_ha = deltas_ha;
        state->have_first_step_delta = true;
    }

    int n_satisfied = 0;
    for (int j = 0; j < n_bands; ++j) {
        const double delta_ha = deltas_ha[static_cast<std::size_t>(j)];
        const bool abs_ok = opts.eigenvalue_abs_break_ha > 0.0
            && delta_ha <= opts.eigenvalue_abs_break_ha;

        bool rel_ok = false;
        if (opts.eigenvalue_rel_break > 0.0 && state->have_first_step_delta) {
            const double first_delta_ha = state->first_step_delta_ha[static_cast<std::size_t>(j)];
            rel_ok = delta_ha <= opts.eigenvalue_rel_break * first_delta_ha;
        }

        if (abs_ok || rel_ok) {
            ++n_satisfied;
        }
    }