TabPack: Efficient Hyperparameter Ensembles for Tabular Deep Learning
Reviewed by Pith2026-07-07 13:39 UTCglm-5.2pith:L7LARWDBopen to challenge →
The pith
Tuning-free tabular model matches tuned baselines at 1/20th the compute
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper shows that for tabular deep learning, the traditional hyperparameter tuning loop can be replaced by a single run that samples many configurations in parallel and lets greedy ensemble selection find what works. The authors demonstrate this with a packed-ensemble architecture where heterogeneous MLPs are stacked along a new dimension and trained together via batched matrix operations, with ensemble members chosen online based on validation performance. The result is that default TabPack on a MacBook runs faster than tuning some baselines on an A100 GPU, while achieving comparable or better mean rank across 17 medium-to-large datasets. The paper also finds that online ensemble (re-e-e
What carries the argument
Packed hyperparameter ensembling: stacking m MLPs with different hyperparameters into a single tensor module, training them in parallel via batched matrix multiplications, and selecting ensemble members greedily during training using validation-set performance as the ensemble score.
If this is right
- Practitioners can skip expensive hyperparameter search for tabular MLPs by running TabPack once with default sampling ranges, reducing experiment cycles from days to hours.
- The packed-ensemble pattern could extend to other parts of the training pipeline — loss functions, data preprocessing, architectural choices — diversifying any vectorizable degree of freedom without separate training runs.
- The finding that hyperparameter diversity primarily enables tuning-free workflows rather than improving raw ensemble quality suggests that future tabular architectures should be designed with built-in configuration robustness rather than relying on external search.
- The ability to run competitively on consumer hardware (MacBook M4 Pro) shifts the accessibility boundary for tabular deep learning, potentially broadening adoption beyond GPU-equipped research labs.
Load-bearing premise
The claim that TabPack is tuning-free rests on the assumption that the authors' default hyperparameter sampling ranges (e.g., depth 1-3, width 384, learning rate from a fixed log-uniform interval) are good enough across all tabular datasets. If these ranges are poorly suited to a new domain, performance could degrade with no recourse beyond adjusting the ranges — which is itself a form of tuning. The paper evaluates on 17 datasets but does not test sensitivity to range miss
What would settle it
Run TabPack on a new tabular domain where the optimal hyperparameters fall outside the default sampling ranges (e.g., where depth >3 or learning rates outside the specified log-uniform interval are needed) and check whether mean rank degrades relative to tuned baselines.
Figures
read the original abstract
In deep learning for tabular data, efficient ensembles of multilayer perceptrons (MLPs) have recently emerged as effective and practical architectures. Existing methods of this kind use the same hyperparameters for all underlying MLPs, which requires hyperparameter tuning for achieving the best performance. In this work, we introduce TabPack, an efficient MLP ensemble with strong out-of-the-box performance and reduced reliance on traditional tuning. In a single run, TabPack samples and trains many MLPs with different hyperparameters efficiently in parallel and selects ensemble members on the fly during training. Thus, TabPack only requires specifying ranges from which to sample MLP hyperparameter rather than exact hyperparameter values, which naturally demands less precision for good performance. In experiments on medium-to-large public datasets, TabPack with default settings performs on par with extensively tuned prior methods, thus substantially reducing effort and compute resources needed to achieve competitive results on tabular tasks. Notably, running the default TabPack configuration on a modern MacBook took less time than tuning some baselines on an industry-grade GPU.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces TabPack, an efficient ensemble of MLPs with randomly sampled hyperparameters for tabular deep learning. The core idea is to pack many MLPs with diverse hyperparameters (depth, dropout, learning rate, etc.) into a single model, train them in parallel, and select ensemble members online during training. This eliminates the need for per-dataset hyperparameter tuning. Experiments on 17 medium-to-large datasets show that a single tuning-free run of TabPack achieves mean rank 2.6, competitive with extensively tuned TabM (rank 2.8) and RealMLP (rank 3.6), while requiring substantially less compute (2.4h total vs 47.2h and 250.9h respectively). Additional evaluations on TabArena and large-scale datasets (Appendix A.1, A.2) provide further evidence of generalizability.
Significance. The paper makes a practical and well-executed contribution to tabular deep learning. The core technical idea of packing heterogeneous-architecture MLPs into a single trainable module (Model Pack and Optimizer Pack, Section 3.3-3.4) is clean and the implementation is non-trivial. The experimental methodology is thorough: 17 datasets, multiple baselines with 100+ tuning iterations, a conservative multi-seed evaluation protocol, per-dataset results with standard deviations (Table 14), ablations (Table 1, Figure 8), and additional benchmarks (Appendix A.1, A.2). The falsifiable claim that TabPack on a MacBook outperforms tuned baselines on an A100 in terms of total compute is a striking and verifiable result. The analysis in Section 5.1 showing that hyperparameter diversity's main role is enabling the tuning-free workflow rather than improving raw performance is a valuable insight. Reproducible code is provided.
major comments (3)
- §3.7 and Table 7: The central 'tuning-free' claim depends on the default hyperparameter sampling ranges (e.g., depth UniformInt[1,3], width 384, Muon LR LogUniform[1e-3,1e-1]). The paper does not describe how these ranges were selected. Given that the benchmark (derived from Gorishniy et al. 2025) and the method share authors, there is a risk that the ranges were refined based on performance on these same 17 datasets, which would make the 'tuning-free' claim partially circular (tuning happened at the range-design level). The independent evaluations in Appendix A.1 and A.2 provide partial mitigation, but the TabArena evaluation (Appendix A.2) switches the ensemble score from validation metric to training loss, which is itself a dataset-specific adjustment. The paper should explicitly state how the ranges in Table 7 were chosen (e.g., based on prior work, held-out datasets, or intuition) —
- §3.5 and Appendix A.2 implementation note: The switch from validation metric to training loss as the ensemble score for TabArena is presented as a practical adjustment, but it is a dataset-specific hyperparameter choice that sits in tension with the 'tuning-free' framing. The paper should either (a) run TabArena with the default validation-metric ensemble score and report the resulting performance drop, or (b) explicitly acknowledge this as a limitation and discuss when users should expect to make such adjustments. As stated, the reader cannot assess how much the 'tuning-free' claim is weakened by this adjustment.
- §5.1, Table 1: TabPack_SameHP achieves rank 1.4±0.7 vs TabPack's 1.6±0.6, meaning traditional per-dataset tuning of TabPack's architecture actually outperforms the tuning-free default. The paper frames this as 'the tuning slightly improves the performance at the cost of noticeable increase of the total runtime.' However, the rank difference (1.4 vs 1.6) is within one standard deviation, and the paper does not test whether this difference is statistically significant. Given that this comparison directly bears on the claim that hyperparameter diversity is 'a reasonable default strategy' (§5.1), a statistical test or a more careful discussion of whether the difference is meaningful would strengthen the conclusion.
minor comments (7)
- Figure 6 (left): The triangle-square-triangle markers for dataset groups are explained in the legend but the specific group assignments per dataset are not immediately clear. Consider adding a table or annotation clarifying which datasets fall into 'worst 25%,' 'middle 50%,' and 'best 25%' groups.
- §3.3: The statement 'one can usually use smaller maximum widths and depths than in traditional single models' is not directly supported by the experiments. Table 7 shows width is fixed at 384, which is within the tuning range of baselines (UniformInt[64,1024] for TabM in Table 10). Consider softening this claim or providing evidence.
- Appendix A.3: The 'thought experiment' about why TabPack performs well on large regression tasks is speculative. While clearly labeled as such, it could benefit from being shortened or moved to a discussion of limitations, as it does not provide empirical evidence for the proposed mechanisms.
- Table 7: The dropout distribution '{0.0, Uniform[0.0,0.5]}' is ambiguous — it is unclear whether this means 50% chance of dropout=0.0 and 50% chance of sampling from Uniform[0,0.5], or something else. Clarify the mixture probability.
- §4.2: The conservative evaluation protocol reruns TabPack with only the M_ens selected base models. It would be useful to report what fraction of the full performance is retained in the conservative vs optimistic protocol, to quantify the cost of this conservatism.
- Figure 8: The y-axis label 'Rel. improv. over MLP' and the specific values (2.0%-3.0%) are not immediately interpretable. Consider clarifying whether this is the same relative improvement metric used in Figure 6.
- The paper introduces 'new periodic embeddings' in Appendix B but does not compare them against prior PLR or PBLD embeddings. A brief comparison or justification for why a new variant was needed would help readers.
Simulated Author's Rebuttal
We thank the referee for a careful and constructive review. The three major comments all raise legitimate points about the strength of the 'tuning-free' claim and the statistical interpretation of our ablation. We address each below and will revise the manuscript accordingly.
read point-by-point responses
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Referee: §3.7 and Table 7: The central 'tuning-free' claim depends on the default hyperparameter sampling ranges. The paper does not describe how these ranges were selected. Given that the benchmark and the method share authors, there is a risk that the ranges were refined based on performance on these same 17 datasets, which would make the 'tuning-free' claim partially circular.
Authors: The referee raises a valid concern. We will add an explicit description of how the sampling ranges in Table 7 were chosen. To be transparent: the ranges were designed based on our prior experience with tabular MLPs (Gorishniy et al. 2025) and general intuition about reasonable hyperparameter values for this model family, not through systematic optimization on the 17 benchmark datasets. For example, the depth range UniformInt[1,3] and width 384 reflect typical values from prior work; the Muon learning rate range LogUniform[1e-3,1e-1] matches the tuning space used for TabM (Table 11). We agree that some informal iteration on range design is difficult to fully rule out, and we will acknowledge this explicitly in the revised manuscript. The independent evaluations in Appendix A.1 (large-scale datasets) and A.2 (TabArena) provide partial mitigation, as these datasets are not part of the main benchmark. We will state all of this clearly so readers can assess the claim for themselves. revision: yes
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Referee: §3.5 and Appendix A.2 implementation note: The switch from validation metric to training loss as the ensemble score for TabArena is presented as a practical adjustment, but it is a dataset-specific hyperparameter choice that sits in tension with the 'tuning-free' framing. The paper should either (a) run TabArena with the default validation-metric ensemble score and report the resulting performance drop, or (b) explicitly acknowledge this as a limitation and discuss when users should expect to make such adjustments.
Authors: This is a fair point. We will take option (b): explicitly acknowledge this adjustment as a limitation and discuss when users should expect to make it. Specifically, we will note that on datasets with small validation sets (as is common in TabArena), the validation metric becomes a noisier signal for greedy ensemble selection, and using training loss can be more stable. We will add a brief discussion of this trade-off in the revised manuscript. Running TabArena with the default validation-metric ensemble score and reporting the performance drop (option a) is a reasonable suggestion, and we will attempt it if time permits before the camera-ready deadline, but we commit to at least the explicit acknowledgment as a limitation. revision: partial
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Referee: §5.1, Table 1: TabPack_SameHP achieves rank 1.4±0.7 vs TabPack's 1.6±0.6, meaning traditional per-dataset tuning of TabPack's architecture actually outperforms the tuning-free default. The paper frames this as 'the tuning slightly improves the performance at the cost of noticeable increase of the total runtime.' However, the rank difference (1.4 vs 1.6) is within one standard deviation, and the paper does not test whether this difference is statistically significant.
Authors: The referee is correct that the rank difference between TabPack_SameHP (1.4±0.7) and TabPack (1.6±0.6) is within one standard deviation and that we did not test for statistical significance. We will revise the discussion in §5.1 to be more careful: rather than implying that tuning 'slightly improves' performance, we will state that TabPack_SameHP performs comparably to TabPack, with no statistically significant difference detected, and that the main benefit of the tuning-free default is the dramatic reduction in runtime (2.4h vs 65.5h) rather than any performance sacrifice. We will also add a note that the comparison is underpowered for detecting small differences given the number of datasets. The core claim — that random hyperparameter sampling is a reasonable default strategy — is supported by the fact that it achieves statistically indistinguishable performance at a fraction of the cost, not by claiming it outperforms tuning. revision: yes
Circularity Check
No significant circularity; self-citations are for evaluation infrastructure, not for results that define the claim by construction.
full rationale
TabPack's central claim — that a single tuning-free run achieves competitive performance with tuned baselines — is an empirical claim evaluated against external baselines (XGBoost, RealMLP, ModernNCA, TabPFN-3, TabICLv2) from independent groups. The self-citations to Gorishniy et al. (2025) and Rubachev et al. (2025) provide evaluation infrastructure (datasets, preprocessing, metric definitions, experiment protocol) and one baseline (TabM), but none of these citations define TabPack's performance by construction. The default hyperparameter ranges in Table 7 are presented as practical design choices, not as first-principles derivations or predictions. The paper does not claim the ranges are derived from theory; it claims they work empirically. The concern that the ranges might have been informally tuned on the same 17 datasets is a generalizability risk (acknowledged via independent TabArena validation in Appendix A.2 and large-scale evaluation in Appendix A.1), not a circularity in the derivation chain. No step in the paper reduces an output to its input by definition or by self-citation. The one minor issue is that the TabArena evaluation switches the ensemble score from validation metric to training loss (Appendix A.2 implementation note), which is a dataset-specific adjustment, but this is transparently reported and does not constitute a circular argument. Overall, the derivation is self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (6)
- m (number of base models) =
64
- m_ens (max ensemble size) =
32
- p_base (base model early stopping patience) =
16
- p_ens (ensemble early stopping patience) =
32
- Base model width =
384
- Hyperparameter sampling ranges (Table 7) =
e.g., depth [1,3], dropout [0,0.5], LR LogUniform[1e-3,1e-1]
axioms (5)
- standard math Greedy forward ensemble selection (Caruana et al. 2004) produces good ensembles from a pool of candidates
- domain assumption Packed-ensemble style vectorization (Laurent et al. 2023) correctly preserves individual model behavior when models are padded to max dimensions
- ad hoc to paper The default hyperparameter sampling ranges generalize across tabular datasets
- domain assumption Validation set performance is a reliable proxy for test set ensemble quality
- domain assumption Muon optimizer (Jordan et al. 2024) is suitable for tabular MLPs
invented entities (3)
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Model Pack
independent evidence
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Optimizer Pack
independent evidence
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Online ensemble construction
independent evidence
Reference graph
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discussion (0)
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