REVIEW 4 major objections 6 minor 42 references
Regression can be done by classifying a query against a small library of local patterns and reconstructing the output as a weighted mix of their stored responses.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · grok-4.5
2026-07-30 13:45 UTC pith:SDOAJWUL
load-bearing objection Clean pattern-library regression with a useful offline cache of responses; works on the toys, but novelty and efficiency claims stay moderate without baselines. the 4 major comments →
From Classification to Regression: Using a Fruitfly to Solve Equations
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Nonlinear input–output relationships—including dynamical operators, flow maps, and general regression, data-driven or physics-informed—can be replaced by a finite pattern library whose online prediction is softmax-weighted reconstruction of stored pattern responses, giving explicit control of the accuracy–storage–inference trade-off.
What carries the argument
Pattern-library reconstruction: similarities of a query (or its embedding) to stored patterns become softmax activations that form a convex combination of the patterns’ precomputed responses (continuous RHS, discrete flow map, or trainable pattern values), including a fruitfly-style Gaussian “scent” embedding for ordinary regression.
Load-bearing premise
A small finite set of representative patterns, under the chosen similarity and embedding, is expressive enough that convex combinations of their stored responses approximate the true map on the regions that matter, without needing to leave the convex hull of those responses.
What would settle it
On a held-out dynamical regime or 1D target outside the span of the learned patterns, check whether raising pattern count still fails to cut trajectory or test error, or whether recursive prediction drifts because the true response lies outside the convex hull of stored responses.
If this is right
- Online dynamical prediction can drop the global surrogate after training and keep only patterns plus their responses.
- Accuracy, memory, and inference cost become tunable mainly through pattern count, embedding, and top-R sparsity.
- The same classification-then-reconstruct pipeline unifies continuous dynamics, discrete maps, data-driven regression, and physics-informed losses.
- Continual learning can freeze old patterns and add new ones when new regimes appear, without retraining the whole library.
- Predictions stay inside the convex hull of learned responses, which bounds outputs but also limits extrapolation.
Where Pith is reading between the lines
- If pattern locations and scent variances were trained instead of fixed on a grid with |D|/P, the same library size might resolve sharp features with fewer patterns.
- The method sits next to classical local and kernel regressors but compresses the reference set to learned prototypes, so scaling studies versus full Nadaraya–Watson or mixture-of-experts would clarify the real online saving.
- Hull-bounded reconstruction suggests a natural uncertainty flag: large distance from every pattern could mark queries that should not be trusted.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a unified regression-via-classification framework motivated by fruitfly olfaction: a finite library of representative patterns stores associated responses, and a query is mapped to a prediction by softmax-weighted reconstruction of those responses (Eqs. 7–9, 16, 24–25). The same pipeline is applied to continuous-time RHS and discrete flow-map learning for dynamical systems, and—via a Gaussian “scent” embedding—to data-driven and physics-informed 1D regression. An offline–online split is emphasized so that online inference reduces to similarity evaluation and aggregation. Demonstrations include Lotka–Volterra (known and unknown dynamics), Lorenz recursive flow maps with a continual-learning augmentation, and 1D parabola/sine/Poisson examples with relative errors typically ~0.1–3% (up to ~10% on a non-smooth forcing).
Significance. If the approach scales beyond the reported low-dimensional demos, it would offer a compact, controllable alternative to global surrogates for scientific regression and dynamical prediction, with an explicit accuracy–storage–inference knob via library size P and optional top-R sparsity. Strengths include a clean, internally consistent reconstruction formula; a genuine offline–online decomposition; and a unified treatment of operator learning, flow maps, supervised regression, and physics-informed least squares. The continual pattern-augmentation idea for Lorenz is a useful practical contribution. The work does not ship machine-checked proofs or public code in the manuscript, and the efficiency advantage over global models is argued structurally rather than measured; significance therefore hinges on whether modest libraries plus the chosen similarities remain expressive on scientifically relevant regions—an assumption the authors themselves flag.
major comments (4)
- [Abstract; §1; §4.1.2; §6] Abstract, §1, and §6 claim reduced computational/memory demand and explicit accuracy–storage–inference control relative to global surrogates, yet the manuscript reports no FLOPs, wall-clock inference, peak memory, or parameter-count comparisons against the neural emulators used offline, nor against standard local/kernel baselines (Nadaraya–Watson, RBF, partition-of-unity, piecewise-affine). For Lotka–Volterra (§4.1.2) a 3×128 network is trained for ~500K iterations then discarded; only trajectory error is shown. Without a quantitative baseline table, the central efficiency claim remains unsupported even if the reconstruction formulas are correct.
- [§3.1–3.2; §4.1–4.2] §3.1–3.2 introduce the pattern library P={v_k} and losses L_RHS / L_traj, but the optimization of the pattern locations v_k themselves is underspecified: initialization, whether v_k are free parameters or selected from data, joint vs staged training with f_θ/M_θ, and any regularization against redundant patterns are not stated. Figures 1–3 and 5–7 cannot be reproduced from the text alone, and the claimed compactness (nP parameters) depends on this procedure. A precise algorithm box or pseudocode for offline pattern identification is needed.
- [§3.1 (after Eq. 9); §3.3; §5; §6] After Eq. (9) predictions are confined to the convex hull of stored responses; §3.3 further fixes scent variances to |D|/P and uses equidistant pattern sites in 1D only. All dynamical demos are 2–3D and regression demos are scalar 1D. This is consistent but load-bearing for the generality claim (“nonlinear input–output relationships,” “scientific data”). The manuscript should either (i) demonstrate at least one higher-dimensional or non-convex-response regime where the hull limitation is stress-tested, or (ii) clearly scope the claims to settings where local responses are well approximated by convex combinations of a small library, with failure modes discussed.
- [§4.2; Fig. 5–7] Lorenz results (§4.2, Fig. 5) report ~1% average ℓ2 on t∈[0,10] recursive rollouts and a continual-learning gain after reinitialization at t=8 (Fig. 7). For a chaotic system this metric alone is weak: there is no reporting in Lyapunov-time units, attractor statistics (e.g., climate error), ensemble of ICs beyond “10 trajectories,” or comparison to simply retaining the trained flow-map network. The reinitialization step also removes the hardest part of long-horizon chaos, so the continual-learning claim should be restated more carefully and supplemented with chaos-appropriate diagnostics.
minor comments (6)
- [§4.1; affiliations; figures] Typos and naming inconsistencies: “Lotka-V oletrra” / “Lotka-Voletrra” (Fig. 1 caption), “W A” in affiliations, double commas in parameter lists (§4.1), and “Fruitfly” vs “fruit fly” / “fruitfly” mixed throughout.
- [Fig. 2–3, 6, 8–9] Figure 8–9 captions begin with a stray period (“Figure 8: . Results…”). Several figures lack axis labels or colorbar legends sufficient to read pattern-index partitions (Fig. 2–3, 6).
- [§3.1; Eq. 10] Softmax temperature τ is introduced as possibly learnable or fixed to 1/√n (§3.1) but never reported for the experiments; likewise top-R / ε sparsity is defined (Eq. 10) but unused in results.
- [§1; §3.3] Related-work positioning vs kernel/Nadaraya–Watson and mixture-of-experts is present but brief; a short explicit contrast table (what is stored, what is evaluated online, dependence on N vs P) would help readers.
- [§5.2; Eq. 32] Physics-informed Poisson (§5.2): how second derivatives of wk are obtained (analytic vs autodiff) and enforcement of Dirichlet BCs are not stated; BC treatment affects the least-squares problem in Eq. (32).
- [Title page] arXiv id / date line says “July 30, 2026” which appears to be a placeholder; fix metadata before journal submission.
Circularity Check
Method-plus-demo paper; pattern library is fit by design and evaluated on held-out/integrated quantities—no derivation that redefines the target as its own input.
full rationale
The central construction (Eqs. 7–9, 16, 24–25) is an explicit surrogate: learn a finite pattern library offline, then form online predictions as softmax-weighted convex combinations of stored responses. Pattern values (and optional emulator weights) are optimized against data residuals, trajectory rollouts, or physics residuals by design; reported errors are on integrated trajectories, test points, or PDE residuals, not tautological restatements of the fit. The convex-hull limitation after Eq. 9 is an expressivity bound the authors state openly, not a hidden circular reduction. Self-citations ([36], [41], [42]) are peripheral related-work pointers (multifidelity/continual learning, chaos-aided classification) and do not underwrite uniqueness or force the main claims. Distinctions from kernels, Nadaraya–Watson, local regression, and MoE are argued rather than smuggled. No step reduces a claimed prediction to its fitted input by construction. Score 1 only for ordinary non-load-bearing author self-citation.
Axiom & Free-Parameter Ledger
free parameters (7)
- Number of patterns P =
task-dependent (e.g. 16–32 dynamics; 10–100 regression)
- Softmax temperature τ =
not systematically reported per experiment
- Scent variances σ_P² and σ_Q² =
|D|/P and |D|/n
- Scent sampling dimension n and sample locations z_i =
n=P in reported 1D runs
- Trainable pattern responses ũ_Pk or f_θ(v_k) / M_θ(v_k) =
fit per task (least squares or NN training)
- Neural emulator architecture and training budget =
e.g. 3 hidden layers × 128; ~500K iters (LV)
- Top-R / threshold ε sparsity (optional) =
optional; not central in reported figures
axioms (5)
- standard math Standard autonomous ODE / discrete flow-map and supervised regression problem statements (Eqs. 1–3, 15, 18).
- domain assumption Scientific trajectories/data occupy limited recurring regions of input space, so a finite pattern library can represent the map locally.
- ad hoc to paper Similarity in the chosen embedding (inner product on states, or Gaussian scent overlap) ranks dynamically/functionally relevant patterns.
- ad hoc to paper Softmax weights yield a useful convex combination of stored responses (prediction in conv(hull) of pattern responses).
- domain assumption For physics-informed Poisson, second derivatives of softmax weights times pattern values form a valid residual minimizer under Dirichlet conditions.
invented entities (2)
-
Pattern library P = {v_k} with stored responses as computational primitives for regression-via-classification
no independent evidence
-
Fruitfly regressor (Gaussian scent embeddings for query and pattern points, sampled to vectors, softmax mix of trainable ũ_Pk)
no independent evidence
Cite this review
Pith. "Pith review of From Classification to Regression: Using a Fruitfly to Solve Equations." pith.science (2026). https://pith.science/paper/SDOAJWUL
@misc{pith2026260727196,
author = {Pith},
title = {Pith review of: From Classification to Regression: Using a Fruitfly to Solve Equations},
year = {2026},
howpublished = {\url{https://pith.science/paper/SDOAJWUL}},
note = {Machine review of arXiv:2607.27196}
}
read the original abstract
We present a novel approach to regression tasks using classification which is motivated by the mechanism used by fruitflies to sense their environment. Specifically, we formulate a general framework for learning nonlinear input-output relationships by replacing complex global surrogate models with a finite library of representative local patterns. Since scientific data often occupy limited and recurring regions of the input space, we generate predictions by measuring similarities between a query and stored patterns, then combining their associated responses through weighted reconstruction. We apply this approach to nonlinear dynamical systems, data-driven regression, and physics-informed learning using suitable embeddings and similarity measures. For dynamical systems, our offline-online workflow extracts patterns from data or governing equations during the offline phase, while online prediction requires only similarity evaluation and response aggregation. This structure helps us reduce computational and memory demands while providing explicit control over the trade-off among accuracy, storage, and inference cost.
Figures
Reference graph
Works this paper leans on
-
[1]
Reduced-order modeling: new approaches for computational physics
David J Lucia, Philip S Beran, and Walter A Silva. Reduced-order modeling: new approaches for computational physics. Progress in Aerospace Sciences, 40(1-2):51–117, 2004
2004
-
[2]
Model reduction and approximation: theory and algorithms
Peter Benner, Mario Ohlberger, Albert Cohen, and Karen Willcox. Model reduction and approximation: theory and algorithms. SIAM, 2017
2017
-
[3]
Model reduction for flow analysis and control
Clarence W Rowley and Scott TM Dawson. Model reduction for flow analysis and control. Annual Review of Fluid Mechanics, 49:387–417, 2017
2017
-
[4]
Kernel methods in machine learning
Thomas Hofmann, Bernhard Schölkopf, and Alexander J Smola. Kernel methods in machine learning. 2008
2008
-
[5]
Kernel methods for pattern analysis
John Shawe-Taylor and Nello Cristianini. Kernel methods for pattern analysis. Cambridge University Press, 2004
2004
-
[6]
Gaussian processes for regression
Christopher Williams and Carl Rasmussen. Gaussian processes for regression. Advances in neural information processing systems, 8, 1995
1995
-
[7]
A tutorial on gaussian process regression: Modelling, exploring, and exploiting functions
Eric Schulz, Maarten Speekenbrink, and Andreas Krause. A tutorial on gaussian process regression: Modelling, exploring, and exploiting functions. Journal of Mathematical Psychology, 85:1–16, 2018
2018
-
[8]
An intuitive tutorial to gaussian process regression
Jie Wang. An intuitive tutorial to gaussian process regression. Computing in Science & Engineering, 25(4):4–11, 2023
2023
-
[9]
Radial basis functions
Martin Dietrich Buhmann. Radial basis functions. Acta Numerica, 9:1–38, 2000
2000
-
[10]
A radial basis function method for the shallow water equations on a sphere
Natasha Flyer and Grady B Wright. A radial basis function method for the shallow water equations on a sphere. Proceedings: Mathematical, Physical and Engineering Sciences, pages 1949–1976, 2009
1949
-
[11]
Deep learning: Foundations and concepts
Christopher M Bishop and Hugh Bishop. Deep learning: Foundations and concepts. Springer Nature, 2023
2023
-
[12]
Understanding deep learning
Simon JD Prince. Understanding deep learning. MIT press, 2023
2023
-
[13]
Deep learning with Python
Francois Chollet and François Chollet. Deep learning with Python. simon and schuster, 2021
2021
-
[14]
Testing the manifold hypothesis
Charles Fefferman, Sanjoy Mitter, and Hariharan Narayanan. Testing the manifold hypothesis. arXiv preprint arXiv:1310.0425, 2013
Pith/arXiv arXiv 2013
-
[15]
Geometry from a time series
Norman H Packard, James P Crutchfield, J Doyne Farmer, and Robert S Shaw. Geometry from a time series. Physical Review Letters, 45(9):712, 1980
1980
-
[16]
Locally weighted regression: an approach to regression analysis by local fitting
William S Cleveland and Susan J Devlin. Locally weighted regression: an approach to regression analysis by local fitting. Journal of the American Statistical Association, 83(403):596–610, 1988
1988
-
[17]
The approximation power of moving least-squares
David Levin. The approximation power of moving least-squares. Mathematics of Computation, 67(224):1517– 1531, 1998
1998
-
[18]
Analysis of moving least squares approximation revisited
Davoud Mirzaei. Analysis of moving least squares approximation revisited. Journal of Computational and Applied Mathematics, 282:237–250, 2015
2015
-
[19]
The partition of unity finite element method: basic theory and applications
Jens M Melenk and Ivo Babuška. The partition of unity finite element method: basic theory and applications. Computer Methods in Applied Mechanics and Engineering, 139(1-4):289–314, 1996
1996
-
[20]
The partition of unity method
Ivo Babuška and Jens M Melenk. The partition of unity method. International Journal for Numerical Methods in Engineering, 40(4):727–758, 1997. 15 Using a Fruitfly to Solve EquationsA PREPRINT
1997
-
[21]
Probabilistic partition of unity networks for high-dimensional regression problems
Tiffany Fan, Nathaniel Trask, Marta D’Elia, and Eric Darve. Probabilistic partition of unity networks for high-dimensional regression problems. International Journal for Numerical Methods in Engineering, 124(10): 2215–2236, 2023
2023
-
[22]
A clustering technique for the identification of piecewise affine systems
Giancarlo Ferrari-Trecate, Marco Muselli, Diego Liberati, and Manfred Morari. A clustering technique for the identification of piecewise affine systems. Automatica, 39(2):205–217, 2003
2003
-
[23]
Piecewise affine regression via recursive multiple least squares and multicategory discrimination
Valentina Breschi, Dario Piga, and Alberto Bemporad. Piecewise affine regression via recursive multiple least squares and multicategory discrimination. Automatica, 73:155–162, 2016
2016
-
[24]
A piecewise linear regression and classification algorithm with application to learning and model predictive control of hybrid systems
Alberto Bemporad. A piecewise linear regression and classification algorithm with application to learning and model predictive control of hybrid systems. IEEE Transactions on Automatic Control, 68(6):3194–3209, 2022
2022
-
[25]
Nonlinear model order reduction based on local reduced- order bases
David Amsallem, Matthew J Zahr, and Charbel Farhat. Nonlinear model order reduction based on local reduced- order bases. International Journal for Numerical Methods in Engineering, 92(10):891–916, 2012
2012
-
[26]
Breaking the kolmogorov barrier in model reduction of fluid flows
Shady E Ahmed and Omer San. Breaking the kolmogorov barrier in model reduction of fluid flows. Fluids, 5(1): 26, 2020
2020
-
[27]
Can a fruit fly learn word embeddings? arXiv preprint arXiv:2101.06887, 2021
Yuchen Liang, Chaitanya K Ryali, Benjamin Hoover, Leopold Grinberg, Saket Navlakha, Mohammed J Zaki, and Dmitry Krotov. Can a fruit fly learn word embeddings? arXiv preprint arXiv:2101.06887, 2021
Pith/arXiv arXiv 2021
-
[28]
Embedology
Tim Sauer, James A Yorke, and Martin Casdagli. Embedology. Journal of Statistical Physics, 65(3):579–616, 1991
1991
-
[29]
Adaptive mixtures of local experts
Robert A Jacobs, Michael I Jordan, Steven J Nowlan, and Geoffrey E Hinton. Adaptive mixtures of local experts. Neural Computation, 3(1):79–87, 1991
1991
-
[30]
Out- rageously large neural networks: The sparsely-gated mixture-of-experts layer
Noam Shazeer, Azalia Mirhoseini, Krzysztof Maziarz, Andy Davis, Quoc Le, Geoffrey Hinton, and Jeff Dean. Out- rageously large neural networks: The sparsely-gated mixture-of-experts layer. arXiv preprint arXiv:1701.06538, 2017
Pith/arXiv arXiv 2017
-
[31]
Ensemble and mixture-of-experts DeepONets for operator learning
Ramansh Sharma and Varun Shankar. Ensemble and mixture-of-experts DeepONets for operator learning. arXiv preprint arXiv:2405.11907, 2024
Pith/arXiv arXiv 2024
-
[32]
Regression by classification
Luís Torgo and Joao Gama. Regression by classification. In Brazilian symposium on artificial intelligence, pages 51–60. Springer, 1996
1996
-
[33]
Regression as classification
Raied Salman and V ojislav Kecman. Regression as classification. In 2012 Proceedings of IEEE Southeastcon, pages 1–6. IEEE, 2012
2012
-
[34]
Cluster-based reduced-order modelling of a mixing layer
Eurika Kaiser, Bernd R Noack, Laurent Cordier, Andreas Spohn, Marc Segond, Markus Abel, Guillaume Daviller, Jan Östh, Siniša Krajnovi´c, and Robert K Niven. Cluster-based reduced-order modelling of a mixing layer. arXiv preprint arXiv:1309.0524, 2013
Pith/arXiv arXiv 2013
-
[35]
Cluster-based network modeling—from snapshots to complex dynamical systems
Daniel Fernex, Bernd R Noack, and Richard Semaan. Cluster-based network modeling—from snapshots to complex dynamical systems. Science Advances, 7(25):eabf5006, 2021
2021
-
[36]
A multifidelity deep operator network approach to closure for multiscale systems
Shady E Ahmed and Panos Stinis. A multifidelity deep operator network approach to closure for multiscale systems. Computer Methods in Applied Mechanics and Engineering, 414:116161, 2023
2023
-
[37]
Maziar Raissi, Paris Perdikaris, and George Em Karniadakis. Physics-informed neural networks: A deep learning framework for solving forward and inverse problems involving nonlinear partial differential equations. Journal of Computational Physics, 378:686–707, 2019. doi:10.1016/j.jcp.2018.10.045
-
[38]
Weighted Nadaraya–Watson regression estimation
Zongwu Cai. Weighted Nadaraya–Watson regression estimation. Statistics & Probability Letters, 51(3):307–318, 2001
2001
-
[39]
A least squares radial basis function partition of unity method for solving pdes
Elisabeth Larsson, Victor Shcherbakov, and Alfa Heryudono. A least squares radial basis function partition of unity method for solving pdes. SIAM Journal on Scientific Computing, 39(6):A2538–A2563, 2017
2017
-
[40]
A comprehensive survey of continual learning: Theory, method and application
Liyuan Wang, Xingxing Zhang, Hang Su, and Jun Zhu. A comprehensive survey of continual learning: Theory, method and application. IEEE Transactions on Pattern Analysis and Machine Intelligence, 46(8):5362–5383, 2024
2024
-
[41]
A multifidelity approach to continual learning for physical systems
Amanda Howard, Yucheng Fu, and Panos Stinis. A multifidelity approach to continual learning for physical systems. Machine Learning: Science and Technology, 5(2):025042, 2024
2024
-
[42]
Enhancing classification accuracy through chaos
Panos Stinis. Enhancing classification accuracy through chaos. arXiv preprint arXiv:2603.15299, 2026. 16
Pith/arXiv arXiv 2026
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.