Towards an Optimal Bound for the Interleaving Distance on Mapper Graphs
Pith reviewed 2026-05-22 21:05 UTC · model grok-4.3
The pith
Integer linear programs provide the first framework for bounding the interleaving distance on mapper graphs
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The authors show that two integer linear programs can bound the interleaving distance on mapper graphs. For any fixed n, the first program decides if an n-interleaving exists between two given mapper graphs, and the second program identifies the assignment of maps that achieves the smallest loss value. Because the loss from prior work upper-bounds the true distance, the minimal loss supplies a computable upper bound. The approach is evaluated on small graphs with known distances and on benchmark and simulated data to illustrate its use in classification tasks.
What carries the argument
Integer linear programs that encode the existence of an n-interleaving or minimize the loss over possible assignments between two mapper graphs
If this is right
- If an ILP for a fixed n returns a feasible solution, the interleaving distance between the two mapper graphs is at most n.
- The smallest loss found for a given n supplies a concrete numerical upper bound on the distance.
- The resulting bounds can be used directly for classification or clustering tasks that compare mapper graphs from different datasets.
- The same ILP formulations apply both to small examples where the distance is known exactly and to larger simulated and benchmark collections.
Where Pith is reading between the lines
- If the ILPs remain tractable on larger mapper graphs, the bounds could support similarity queries on streaming or incrementally built data summaries.
- Because the exact interleaving distance on the underlying Reeb graphs is NP-hard, these ILP bounds offer a practical relaxation whose tightness can be measured on the discrete mapper case.
- Optimizing the ILP over the choice of n itself might yield the exact distance in cases where the minimal loss reaches zero.
Load-bearing premise
The loss function is assumed to give a valid upper bound on the true interleaving distance, and the ILP constraints are assumed to correctly capture when an n-interleaving exists.
What would settle it
On any pair of mapper graphs whose exact interleaving distance is known by other means, the minimal loss returned by the second ILP is strictly smaller than that known distance.
Figures
read the original abstract
Mapper graphs are widely used tools in topological data analysis and visualization. They can be understood as discrete approximations of Reeb graphs, providing insight into the shape and connectivity of complex data. Given a high-dimensional point cloud together with a real-valued function defined on it, a mapper graph summarizes the induced topological structure: each node represents a local neighborhood, and edges connect nodes whose corresponding neighborhoods overlap. Our focus is the interleaving distance for mapper graphs, arising as a discretized analogue of the interleaving distance for Reeb graphs-a quantity known to be NP-hard to compute. This distance measures how similar two mapper graphs are by quantifying how much they must be ``stretched'' to be made comparable. Recent work introduced a loss function that gives an upper bound on this distance. The loss evaluates how far a given collection of maps, called an assignment, is from being a true interleaving. Importantly, it is computationally tractable, offering a practical way to bound the distance, however the quality of the bound is dependent on the choice of assignment. In this paper, we develop the first framework for bounding the interleaving distance on mapper graphs. We present the bound in two ways: first, by formulating an integer linear program (ILP) that determines whether an $n$-interleaving exists for a given $n$; and second, by constructing an ILP that identifies an assignment with minimal loss for that $n$. We also evaluate the method on small examples where the interleaving distance is known, and on benchmark and simulated datasets, demonstrating the utility of the approach for classification tasks based on mapper graphs.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims to develop the first framework for bounding the interleaving distance on mapper graphs. It does so by presenting two ILP formulations—one that decides the existence of an n-interleaving for a fixed n, and one that finds an assignment minimizing the loss from prior work for that n—thereby producing a computable upper bound. The approach is evaluated on small instances whose true distances are known by other means as well as on benchmark and simulated datasets, with demonstrated utility for classification tasks based on mapper graphs.
Significance. If the ILP encodings are faithful and the loss function supplies a valid upper bound, the work supplies the first practical algorithmic method for a quantity whose exact computation is NP-hard. The explicit ILP constructions together with the evaluation on instances with independently known distances constitute a concrete, falsifiable contribution that could be adopted for mapper-graph comparisons in topological data analysis.
minor comments (3)
- The manuscript should include a short table or paragraph in the evaluation section listing the sizes of the small instances (number of nodes/edges) and the wall-clock times required to solve the two ILPs; without these data it is difficult to judge scalability even for the “small” regime.
- In the ILP formulations, the meaning of each binary variable and each family of constraints should be stated explicitly in a single dedicated paragraph or table immediately after the mathematical program is displayed; current notation leaves some auxiliary variables implicit.
- A brief comparison, even on the small examples, between the bound obtained by the new minimal-loss ILP and the bound obtained by the heuristic assignment method of the cited prior work would strengthen the claim that the ILP improves upon existing practice.
Simulated Author's Rebuttal
We thank the referee for the positive summary of our contribution and for recommending minor revision. No major comments appear in the report.
Circularity Check
No significant circularity
full rationale
The paper's central contribution is the explicit construction of two new ILP formulations: one to decide existence of an n-interleaving and one to minimize the loss of an assignment for fixed n. These are presented as algorithmic encodings of combinatorial conditions that were previously intractable. The loss function itself is imported from prior work as an external upper bound; the paper does not redefine the distance in terms of the loss or fit parameters to the target quantity and then relabel the fit as a prediction. No self-citation chain is invoked to justify uniqueness or to smuggle an ansatz, and no renaming of known empirical patterns occurs. The derivation chain is therefore self-contained: the ILPs are new objects whose correctness is asserted by direct encoding rather than by reduction to the paper's own fitted outputs.
Axiom & Free-Parameter Ledger
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