The depth of the hierarchy directly influences pruning effectiveness; a 44‑level tree yields the best trade‑off.
| Component | Specification | |-----------|----------------| | | 2 × Intel Xeon E5‑2680 v4, 256 GB RAM | | Software | C++17 implementation, compiled with -O3 ; Python 3.10 for data generation | | Baselines | Heap‑Top (exact), Count‑Sketch‑Top (ε = 0.01), Space‑Saving‑Top (k = k) | | Datasets | • Synthetic Gaussian (μ = 0, σ = 1) – 100 M items • Synthetic Zipf (α = 1.2) – 200 M items • Real‑world Click‑stream (Yahoo! R6) – 150 M items | | Metrics | 1‑latency (ms), 2‑throughput (M updates/s), 3‑relative error (|est‑k−true‑k|/true‑k) | xhmster 44 top