Amortized Optimal Transport from Sliced Potentials
Pith reviewed 2026-05-10 09:47 UTC · model grok-4.3
The pith
Sliced optimal transport potentials can amortize the prediction of full optimal transport plans across many measure pairs.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Kantorovich potentials from sliced optimal transport serve as predictors for the potentials of the full optimal transport problem. A functional regression model is fit by least-squares methods in RA-OT, or its parameters are estimated by optimizing the Kantorovich dual objective in OA-OT. The predicted OT plan is then recovered from the estimated potentials. This yields amortized solvers that reuse information across multiple measure pairs, remain parsimonious, and do not depend on structures such as the number of atoms in the discrete case.
What carries the argument
The RA-OT regression and OA-OT dual-optimization models that map sliced OT Kantorovich potentials to full OT potentials for subsequent plan recovery.
Load-bearing premise
Kantorovich potentials obtained from sliced OT contain enough information to accurately predict or optimize the full OT potentials via regression or dual objectives.
What would settle it
On held-out pairs of measures, compare the transport cost or plan recovered from the amortized potentials against the cost or plan from directly solving the full OT problem; large discrepancies would show the sliced potentials are not sufficiently informative.
Figures
read the original abstract
We propose a novel amortized optimization method for predicting optimal transport (OT) plans across multiple pairs of measures by leveraging Kantorovich potentials derived from sliced OT. We introduce two amortization strategies: regression-based amortization (RA-OT) and objective-based amortization (OA-OT). In RA-OT, we formulate a functional regression model that treats Kantorovich potentials from the original OT problem as responses and those obtained from sliced OT as predictors, and estimate these models via least-squares methods. In OA-OT, we estimate the parameters of the functional model by optimizing the Kantorovich dual objective. In both approaches, the predicted OT plan is subsequently recovered from the estimated potentials. As amortized OT methods, both RA-OT and OA-OT enable efficient solutions to repeated OT problems across different measure pairs by reusing information learned from prior instances to rapidly approximate new solutions. Moreover, by exploiting the structure provided by sliced OT, the proposed models are more parsimonious, independent of specific structures of the measures, such as the number of atoms in the discrete case, while achieving high accuracy. We demonstrate the effectiveness of our approaches on tasks including MNIST digit transport, color transfer, supply-demand transportation on spherical data, and mini-batch OT conditional flow matching.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes two amortized methods (RA-OT and OA-OT) for predicting optimal transport plans across multiple measure pairs. RA-OT performs functional regression treating sliced-OT Kantorovich potentials as predictors and full-OT potentials as responses, estimated by least squares; OA-OT optimizes the parameters of a functional model directly on the Kantorovich dual objective. In both cases the transport plan is recovered from the estimated potentials. The methods are presented as structure-independent, parsimonious, and efficient for repeated OT problems, with empirical demonstrations on MNIST digit transport, color transfer, spherical supply-demand, and mini-batch OT conditional flow matching.
Significance. If the approximation quality holds across the claimed tasks, the work provides a practical route to amortize repeated OT computations by reusing sliced-OT information, which could reduce cost in pipelines that solve many transport problems (e.g., generative modeling or alignment tasks) while remaining independent of discrete support size.
major comments (2)
- [§3 (method description) and §4 (theoretical justification)] The central claim that sliced-OT potentials suffice to recover accurate full-OT plans rests on an unproven identifiability assumption. No theorem, error bound, or identifiability result is supplied showing that the averaged 1-D projections determine (or can approximate to controlled error) the multi-dimensional Kantorovich potentials; the regression or dual optimization may therefore converge to a plan whose coupling deviates substantially from the true OT plan when the measures contain couplings invisible in random projections.
- [Abstract and §5 (experiments)] The abstract and experimental sections state that both RA-OT and OA-OT “achieve high accuracy” on the listed tasks, yet no quantitative metrics (Wasserstein distance, relative error, runtime tables), error bars, ablation on number of slices, or direct comparison to Sinkhorn, entropic OT, or existing amortized baselines are referenced. Without these numbers it is impossible to judge whether the recovered plans are competitive or merely plausible.
minor comments (2)
- [§3.1] Clarify the precise functional form and parameterization of the regression model in RA-OT (e.g., is it a neural network, kernel ridge, or linear functional?) and the initialization strategy for OA-OT.
- [§6 (discussion)] Add a short discussion of failure modes or regimes (e.g., high-dimensional or highly anisotropic measures) where the sliced-potential approximation is expected to degrade.
Simulated Author's Rebuttal
We thank the referee for their constructive comments. We address each major comment point by point below and indicate the revisions we will make to the manuscript.
read point-by-point responses
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Referee: [§3 (method description) and §4 (theoretical justification)] The central claim that sliced-OT potentials suffice to recover accurate full-OT plans rests on an unproven identifiability assumption. No theorem, error bound, or identifiability result is supplied showing that the averaged 1-D projections determine (or can approximate to controlled error) the multi-dimensional Kantorovich potentials; the regression or dual optimization may therefore converge to a plan whose coupling deviates substantially from the true OT plan when the measures contain couplings invisible in random projections.
Authors: We appreciate the referee highlighting this theoretical gap. Our methods are motivated by the practical efficiency of sliced OT potentials as predictors for full OT potentials, building on the established approximation properties of sliced Wasserstein distances. We do not claim or prove that sliced projections universally determine the full Kantorovich potentials, nor do we supply error bounds or an identifiability theorem. The regression and optimization steps are presented as empirical amortization strategies that work well when the sliced information is sufficiently informative. In the revision we will add an explicit discussion of this limitation, clarify the assumptions, and note that a rigorous theoretical analysis of when the approximation holds (or fails) is left for future work. revision: partial
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Referee: [Abstract and §5 (experiments)] The abstract and experimental sections state that both RA-OT and OA-OT “achieve high accuracy” on the listed tasks, yet no quantitative metrics (Wasserstein distance, relative error, runtime tables), error bars, ablation on number of slices, or direct comparison to Sinkhorn, entropic OT, or existing amortized baselines are referenced. Without these numbers it is impossible to judge whether the recovered plans are competitive or merely plausible.
Authors: We agree that quantitative metrics are necessary to substantiate the accuracy claims. The current experiments emphasize visual and qualitative results on MNIST transport, color transfer, spherical data, and conditional flow matching. In the revised manuscript we will expand §5 to include Wasserstein distances to ground-truth OT plans, relative errors, runtime tables, error bars from repeated runs, an ablation study on the number of slices, and direct comparisons against Sinkhorn, entropic OT, and relevant amortized baselines. These additions will be reflected in the abstract as well. revision: yes
Circularity Check
No significant circularity; derivation relies on independent computation of sliced vs. full potentials followed by standard fitting.
full rationale
The paper computes Kantorovich potentials from sliced OT (via 1D projections) as an independent preprocessing step, then trains either a least-squares functional regression (RA-OT) or dual-objective optimization (OA-OT) to map those to full OT potentials before recovering the plan. Training explicitly requires separate computation of both sliced and full potentials on the training measure pairs, so the fitted mapping is not tautological. No equation equates the final plan to a quantity already present in the sliced inputs by construction, no load-bearing self-citation chain is invoked, and the method is presented as an empirical amortizer whose accuracy is validated on downstream tasks rather than derived from its own definitions.
Axiom & Free-Parameter Ledger
Forward citations
Cited by 3 Pith papers
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ASAP: Amortized Doubly-Stochastic Attention via Sliced Dual Projection
ASAP amortizes Sinkhorn-based doubly-stochastic attention by learning a parametric map from 1D potentials to the Sinkhorn dual and reconstructing the plan via two-sided entropic c-transform, delivering 5.3x faster inf...
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Sliced-Regularized Optimal Transport
SROT regularizes the OT plan toward a smoothened sliced OT plan, producing more accurate approximations to exact OT than entropic OT while also improving on the sliced OT reference.
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Sliced-Regularized Optimal Transport
SROT regularizes the OT transport plan toward a sliced OT reference, yielding better approximations of exact OT than entropic OT and improving on the sliced OT plan itself.
Reference graph
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