Research map / Federated learning and privacy / Differential privacy
Scalable Private Partition Selection via Adaptive Weighting
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Proposes MAD and MAD2R, scalable parallel weight-and-threshold algorithms for differentially private partition selection that reroute excess weight to light items, with stochastic dominance over the basic uniform weighting method.
Problem
User-level differentially private partition selection (private set union / key discovery): output as many items as possible from the union of users' sets, in a form that can run in massively parallel systems at very large scale.
Approach
An adaptive, non-uniform weighting that truncates weight above an adaptive threshold and reroutes the excess back to users' other items, with the same sensitivity (and hence noise and threshold) as uniform weighting; a two-round variant reuses noisy round-one weights to prune and bias round-two weights.
Key results
- MAD2R yields the best parallel output size on seven of nine datasets, e.g. 17785 items on Finance vs 16926 for DP-SIPS and 12412 for Basic.
- MAD always outperforms Basic on every dataset, consistent with the stochastic dominance proof (e.g. 35797 vs 35315 on Amazon).
- On Common Crawl (about 800 billion entries), MAD2R outputs 29,373,829 items versus 28,328,613 for DP-SIPS and 15,734,148 for Basic, with parallel runs finishing within 4 hours.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Replace Basic weighting with unbiased adaptive rerouting in MAD | Basic · Higgs, IMDb, Reddit, Finance, Wiki, Twitter, Amazon, Clueweb, and Common Crawl | output size: 1791 -> 1807; 2504 -> 2516; 4062 -> 4162; 12412 -> 12759; 7753 -> 7812; 8859 -> 9074; 35315 -> 35797; 34603077 -> 346921 | Helped |
| Use two-round MAD with first-round weight-based filtering and biased weights | MAD · IMDb, Reddit, Finance, Wiki, Twitter, Amazon, and Common Crawl | output size: 2516 -> 3369; 4162 -> 6215; 12759 -> 17785; 7812 -> 10554; 9074 -> 14064; 35797 -> 67086; 15815452 -> 29373829 | Helped |
| Use two-round MAD instead of DP-SIPS | DP-SIPS · IMDb, Reddit, Finance, Wiki, Twitter, Amazon, and Common Crawl | output size: 3076 -> 3369; 5784 -> 6215; 16926 -> 17785; 9795 -> 10554; 13499 -> 14064; 66126 -> 67086; 28328613 -> 29373829 | Helped |
| Use two-round MAD instead of MAD | MAD · Higgs and Clueweb | output size: 1807 -> 1767; 34692178 -> 34533524 | Hurt |
| Vary the maximum adaptive degree d_max (ablation) | MAD and MAD2R · Reddit | output size | No clear effect |
| Vary privacy parameter epsilon (ablation) | Parallel algorithms on Reddit · Reddit | output size | Helped |
| Vary privacy parameter delta (ablation) | Parallel algorithms on Reddit · Reddit | output size | Helped |
| Vary maximum set size parameter Delta_0 (ablation) | Parallel algorithms on Reddit · Reddit | output size | Mixed |
Surprising findings
- On the small datasets, the sequential PolicyGaussian and GreedyUpdate outperform all parallel methods, with GreedyUpdate's performance strongly dataset-dependent.
- On Clueweb, DP-SIPS outperforms the MAD variants, which the authors attribute to outlier statistics where the number of unique items is less than the number of users.
Limitations
- Sequential baselines (PolicyGaussian, GreedyUpdate) remain better on small datasets, with MAD2R reaching at least 86% of PolicyGaussian's output.
- Parameters such as d_max, beta, b_min, b_max and privacy splits were chosen by the authors, and DP-SIPS was given its best of two privacy splits.
- Experiments use delta=1e-5 for consistency with prior work, while production deployments usually need smaller delta.
Experimental setup
Datasets: Higgs IMDb Reddit Finance Wiki Twitter Amazon Clueweb Common Crawl
Benchmarks: Higgs IMDb Reddit Finance Wiki Twitter Amazon Clueweb Common Crawl
Metrics: output size (number of items released)
Baselines: Basic DP-SIPS PolicyGaussian GreedyUpdate
Builds on: DP-SIPS weight and threshold partition selection Gaussian mechanism PolicyGaussian GreedyUpdate
Closest papers by meaning
- On the Price of Differential Privacy for Hierarchical Clustering (ICLR 2025 · similarity 0.87)
- Lumberjack: Better Differentially Private Random Forests through Heavy Hitter Detection in Trees (NeurIPS 2026 · similarity 0.85)
- Privacy Profiles for Private Selection (ICML 2024 · similarity 0.85)
- Differentially Private Space-Efficient Algorithms for Counting Distinct Elements in the Turnstile Model (ICML 2025 · similarity 0.85)
- It's My Data Too: Private ML for Datasets with Multi-User Training Examples (ICML 2025 · similarity 0.85)
- Differentially Private Set Representations (NeurIPS 2024 · similarity 0.85)
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