用分层近邻图检索相似向量

928    //  greedy search on upper levels929    storage_idx_t nearest = entry_point;930    float d_nearest = qdis(nearest);931932    for (int level = max_level; level >= 1; level--) {933        HNSWStats local_stats =934                greedy_update_nearest(*this, qdis, level, nearest, d_nearest);935        stats.combine(local_stats);936    }937938    int ef = std::max(params ? params->efSearch : efSearch, k);939    if (bounded_queue) { // this is the most common branch940        MinimaxHeap candidates(ef);941942        candidates.push(nearest, d_nearest);943944        search_from_candidates(945                *this, qdis, res, candidates, vt, stats, 0, 0, params);