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REVIEW 3 major objections 5 minor 31 references

Grokking Beyond the Euclidean Norm of Model Parameters

T0 review · 3 major / 5 minor · reviewed 2026-08-07 · deepseek-v4-flash

Pith's one-line read Grokking is a generic effect of any regularizer that biases toward a generalizing structure, with the delay set by the product of learning rate and regularization strength.

desk verdict A real extension of grokking theory beyond ℓ2, but the headline 1/(αβ) delay law is proven only as an upper bound and the 'iff' statements outrun the appendix. read the letter →

arxiv 2506.05718 v2 pith:JUZYCOJ5 submitted 2025-06-06 cs.LG cs.AIstat.ML

classification cs.LGcs.AIstat.ML
keywords grokkingregularizationsparserecoverylow-rankmatrixfactorizationimplicitbiasnuclearnormcoherenceChatterjee-Łojasiewiczinequality
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper aims to show that grokking—the sudden generalization that appears long after a network has memorized its training set—is not special to weight decay. The claim is that whenever a good solution has some structure such as sparsity or low rank, running gradient descent with a small but non-zero regularization toward that structure produces grokking, and the delay between memorization and generalization is set by the inverse of the product of the learning rate and the regularization strength. The proof decomposes training into two phases separated by the moment the loss gradient becomes smaller than the regularizer's subgradient, and the delay formula is verified empirically on modular arithmetic, teacher-student networks, sparse recovery, and matrix factorization. A consequence emphasized by the authors is that the ℓ2 norm of the parameters is not a reliable progress measure when the inductive bias points at a different structure: it can grow while the model still generalizes.

What carries the argument

The load-bearing object is the two-phase decomposition of subgradient descent on the composite objective $g + \beta h$. The first phase is controlled by the $r$-Chatterjee–Łojasiewicz inequality at initialization, $4g(x(0)) < r^2\chi(g, x(0), r)$, which guarantees geometric decay of the loss while iterates stay inside a ball; the condition $\beta\lVert H(x(k))\rVert_2 \leq \gamma\lVert G(x(k))\rVert_2$ ensures the regularizer does not interfere until the loss is nearly minimized. The second phase is governed by the distance-to-set identity $\Delta t = \mathrm{dist}^2(x(t_1), \Theta_f)/(\alpha\beta\eta)$, the ratio of the squared distance from the memorizing iterate to the regularized solution set and the step $\alpha\beta\eta$; this is what makes the grokking delay inversely proportional to $\alpha\beta$. In the linear settings, the robust null space property (or its rank analogue) converts near-equality of the $\ell_1$ (or nuclear) norm with the target into near-recovery of the true solution, closing the loop between regularization and generalization, while the Wedin $\sin\Theta$ bound controls the drift of singular vectors during the late phase.

What would settle it

On a sparse recovery instance where the design matrix satisfies the null space property and the CL condition holds at initialization, vary $\alpha$ and $\beta$ independently over two orders of magnitude and measure the step at which the recovery error first drops below a fixed threshold; if doubling $\alpha$ alone does not halve the required extra time $\Delta t$, the claimed $1/(\alpha\beta)$ scaling is false. A complementary test is to initialize a two-layer ReLU teacher-student at a point where the CL inequality is violated (a flat loss region) and run with small $\ell_1$ regularization; observing grokking there would show the CL condition is not necessary.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that regularized subgradient descent exhibits a provable two-phase dynamic whenever the loss satisfies the Chatterjee–Łojasiewicz inequality at its initialization and the regularization term stays dominated by the loss gradient throughout the first phase. In that setting the iterates first reach an almost-interpolating (memorizing) solution in about $t_1 \approx O\!\left(\log(1/\varepsilon)/\alpha\chi\right)$ steps, and then need an additional $\Delta t \approx \mathrm{dist}^2(x(t_1), \Theta_f)/(\alpha\beta\eta)$ steps to approach the minimizer of the regularized objective, with recovery error of order $O(\alpha\beta + \lVert \xi \rVert)$. For sparse recovery and low-rank matrix sensing and completion, the paper proves that this delay law holds, that the $\ell_1$ or nuclear-norm regularizer is necessary in the shallow case (weight decay alone only yields a memorizing least-squares solution), and that depth or coherence-based data selection can supply the same bias implicitly. The paper further documents, on modular addition and image classification, that $\ell_1$ and nuclear-norm regularization reproduce the grokking curves previously attributed to $\ell_2$, and that the $\ell_2$ norm can rise while generalization is happening.

Load-bearing premise

The clean delay law rests on the loss satisfying the Chatterjee–Łojasiewicz inequality at the exact initialization and on the regularizer's subgradient staying much weaker than the loss gradient until memorization; for nonlinear teacher-student, modular arithmetic, and image data this condition is imported from wide-network theory rather than verified, and the noiseless alignment $\Theta_f \cap \Theta_g \neq \varnothing$ together with the noise bound $\lVert X^\top\xi \rVert_2 \leq \sqrt{C\alpha\beta}$ restricts the $1/(\alpha\beta)$ law to an essentially noiseless regime.

Editorial extensions

If this is right

  • If the central theorem is right, grokking should be reproducible with any regularizer whose bias is aligned with the structure of a good solution—sparsity, low rank, or a domain constraint—and the delay is predictable from $\alpha\beta$ alone.
  • Weight decay is not a necessary condition for grokking, and a decreasing $\ell_2$ norm is not a necessary signature; monitoring the norm of the regularized property, such as the $\ell_1$ or nuclear norm, is the better progress signal.
  • Depth acts as an implicit regularizer that can replace explicit $\ell_1$ or nuclear-norm penalties: deeper linear models grok without explicit regularization in the sparse and low-rank settings studied, and can even un-grok when the bias is no longer needed.
  • Choosing training samples with high leverage scores (coherence) relative to the target low-rank or sparse structure can cut both the number of examples needed and the time to generalization, and this can be done with all other hyperparameters fixed.
  • The scaling $\Delta t \propto 1/(\alpha\beta)$ gives a quantitative handle for scheduling: increasing $\alpha\beta$ accelerates generalization, while keeping it small produces the long delayed-generalization window associated with grokking.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Editorial inference: the theory suggests a practical recipe for inducing grokking in any overparameterized model—identify the known structure of the desired solution, add a small penalty toward it, and tune the delay a priori through the product of learning rate and penalty strength.
  • Editorial inference: the two-phase mechanism closely parallels circuit-competition accounts of grokking; if the late-phase bias is the circuit-selection force, the same $1/(\alpha\beta)$ delay law should appear whenever a slow second-order drift pushes weights from a kernel-like to a structured solution, connecting to feature-learning theories of grokking.
  • Editorial inference: the coherence-based data selection result yields a testable extension—on modular arithmetic or low-rank tasks, training on highest-leverage-score entries should shift the grokking curve left relative to uniform sampling even at a fixed total sample count.
  • Editorial inference: because the $\ell_2$ norm can rise with generalization, previously reported norm-decrease or slingshot phenomena should be re-examined under $\ell_1$ and nuclear regularization; the same phase transition may be visible in the $\ell_1$ or nuclear norm instead.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The paper develops a general theory of grokking as a two-phase phenomenon induced by regularization toward a property P (sparsity, low rank), with a main theorem claiming that after a memorization phase the generalization delay is Δt = dist²(x(t1), Θf)/(αβη) for step size α and regularization strength β. It instantiates this for sparse recovery with ℓ1 regularization and for matrix factorization with nuclear-norm regularization, and it provides extensive experiments on modular arithmetic, teacher-student networks, MNIST, data selection, and depth. It also reports that the ℓ2 norm can rise during generalization when ℓ1/ℓ∗ regularization is used, and it identifies a failure mode called 'grokking without understanding' under large initialization with weight decay.

Significance. If the main theorem's quantitative claim were fully proven, the paper would be a substantial extension of Lyu et al. (2023) and would provide a unifying explanation for regularization-induced grokking beyond ℓ2. The paper's parameter-free delay formula (no fitted constants), its explicit instantiations in linear sparse/low-rank settings, and its broad empirical validation with reproducible code are genuine strengths. The experiments sweeping α and β and reporting t2 ∝ 1/(αβ) are valuable even if the theory currently establishes only an upper bound; however, the missing lower bound in the central theorem means that the headline claim that the delay 'scales like 1/(αβ)' is not yet proven.

major comments (3)
  1. [Theorem 2.1 and Appendix C.1 (Lemma C.12, Theorem C.13)] The 'if and only if' in the second bullet is not established by the proof. Lemma C.12 gives an upper bound on min_{t1≤t≤t2}(f(x(t))−f*), and Theorem C.13 combines it with max∥F∥²≤Cβ² to obtain the implication t2−t1≥R²/(αβη) ⇒ min≤(η+Cαβ)β/2. This is a sufficient condition only; a matching lower bound would require a converse inequality (e.g., a uniform lower bound on ∥F(x(t))∥ or on the rate of decrease of dist(x(t),Θf)), which is not supplied. Since the abstract and Section 2 state the delay 'scales like 1/(αβ)' as an equality-type law, this gap is load-bearing for the paper's central claim. Please either prove the lower bound or restate the theorem as an upper-bound/sufficient condition.
  2. [Theorems 3.1, 3.3, 3.4, 3.5 and proofs C.4–C.7] These results inherit the same unsupported 'iff'. Theorem 3.1 is proved by invoking Theorem C.13, and Theorems 3.3 and 3.5 only add the robust null space or rank null space property on top of that; consequently, the recovery-error statements also hold only as sufficient conditions. The exact thresholds in Lemmas C.31 and C.42 are derived for the pure shrinkage dynamics a_{t+1}=a_t−αβH(a_t) (or, in the matrix case, for the polar subgradient H=UV⊤), but in the actual dynamics (1) the loss gradient G(x(t)) is present and arbitrary subgradient selections are allowed, so those lemmas do not provide the missing lower bound for the full dynamics. Furthermore, for a general H∈∂∥A∥*, the −αW term in the nuclear-norm subgradient can change the singular values beyond the claimed |σ_i−α|, so Lemma C.42 is not valid for arbitrary subgradient selections. The empirical scaling in Figures 4 and 6 supports 1/(αβ) but does not fill this logical gap.
  3. [Section 4 and Theorem 2.1 assumptions] Theorem 2.1 is conditional on g being r-CL at initialization and on β∥H(x(k))∥₂ staying dominated by ∥G(x(k))∥₂ throughout the memorization phase; these conditions are cited from Liu et al. (2021) for wide overparameterized networks but are not verified for the nonlinear teacher-student, modular arithmetic, or MNIST models used in Section 4. The paper should state explicitly that for these models the theoretical delay law is a conjecture supported by experiments, not a theorem.
minor comments (5)
  1. [Theorem 2.1 vs Theorem C.13] Theorem 2.1 writes 't2 > t1 + Δt' while Theorem C.13 and the proofs use 't2 ≥ t1 + Δt'; please make the threshold inequalities consistent across the statements.
  2. [Throughout the text] Typos such as 'coefficent', 'ovaparametrization', 'Cohence', and 'they Assumption 3.2' should be corrected.
  3. [Figure 1 caption] The bottom caption says 'In the case of ℓ1 (top-left)' while referring to bottom panels; please clarify which panel shows which norm dynamics.
  4. [Section 3.5 (Implicit Bias of the Depth)] The notation a = ⊙_{k=1}^L A_k is used without defining the per-layer domain or the corresponding gradient update; please specify A_k ∈ R^n (or the matrix form) and the update rule for the deep parameterization.
  5. [References] At least one bibliography entry contains raw HTML entities such as '&#x2113;'; these should be cleaned up for publication.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the derived 1/(alpha*beta) delay law uses no fitted constants, and the generalization bridge is external compressed-sensing theory.

full rationale

The paper's central quantitative claim is the delay formula Delta_t = dist^2(x(t1), Theta_f)/(alpha*beta*eta). This quantity is derived in Theorem C.13 and Lemma C.12 from the subgradient descent recurrence and the bound ||F(x(t))||^2 = O(beta^2); it contains no fitted parameter later relabeled as a prediction. The experiments sweep alpha and beta and compare against the computed t2, rather than fitting the 1/(alpha*beta) scaling. The bridge from minimizing h over Theta_g to generalization is supplied by external compressed-sensing results (robust null space property and Wedin sin-Theta bounds), not by a self-citation chain. The Chatterjee-Lojasiewicz regularity assumption is cited from Liu et al. (2021), not from the present authors' prior work, and is an assumption about the loss landscape rather than a restatement of the conclusion. The self-reference to Notsawo et al. (2023) appears only in the related-work survey and is not load-bearing. The proof's 'if and only if' in Theorem 2.1 and its instantiations is not actually established by the displayed upper-bound inequality in Lemma C.12; this is a correctness gap about a missing lower bound, not a circular reduction of the prediction to its inputs. No step in the derivation is, by the paper's own equations, equivalent to its input by construction.

Assumptions & free parameters 3 free parameters · 5 assumptions · 0 invented entities

No fitted constants appear in the theory: the delay Δt = dist²(x(t1), Θf)/(αβη) and the error floors O(αβ) and O(∥ξ∥₂) are derived from α, β, and problem geometry. The load-bearing premises are: (1) the r-CL inequality at initialization plus bounded subgradients, which powers the memorization phase and is imported from Chatterjee (2022) and Liu et al. (2021) rather than verified for the nonlinear experiments; (2) Assumption C.5, the alignment of minimizers, which the authors flag as low-noise; (3) the noise bound ∥X⊤ξ∥₂ ≤ √(Cαβ); (4) the robust null space and rank null space properties that connect minimum-h solutions to generalization, imported from Foucart and Rauhut (2013). No invented entities; 'property P' is a re-framing and 'grokking without understanding' is borrowed from Levi et al. (2024). The experimental hyperparameters (ζ, α, β, N) are stated regime choices with reported sensitivity, not ad hoc fitted constants.

free parameters (3)
  • initialization scale ζ (deep sparse recovery) = ζ = 1e-6 (L=1), ζ = 1e-2 (L>1); large ζ = 10 for ℓ2 experiments
    Section F.1 and Figure 7: chosen so depth's implicit bias dominates; the paper reports the transition with ζ, so it is a swept regime knob, not a fitted constant.
  • sparse recovery configuration (n, s, N, α, β) = (102, 5, 30, 1e-1, 1e-5)
    Section 3.1 validation, chosen inside the theorem's regime (N < n, small β); the paper sweeps N, s, α, β and confirms t2 ∝ 1/(αβ), so no constant is fit to force the central curve.
  • matrix completion configuration (n1, n2, r, N, α, β) = (10, 10, 2, 70, 1e-1, 1e-4)
    Section 3.2 validation, chosen inside the theorem's regime; the paper sweeps these to exhibit the singular-value decay dynamics and the t2 ∝ 1/(αβ) scaling.
assumptions (5)
  • domain assumption g satisfies the r-CL inequality at initialization: 4g(x(0)) < r²χ(g, x(0), r)
    Engine of the memorization phase (Theorem 2.1, Theorem C.14); cited from Liu et al. 2021 for wide nets, not verified for the nonlinear experimental models in Section 4.
  • domain assumption Assumption C.5: Θf ∩ Θg ≠ ∅
    Appendix C.1, needed to conclude h(x(t)) → h*_g; the authors themselves remark it 'assumes too little noise compared to the signal'.
  • domain assumption Noise bound ∥X⊤ξ∥₂ ≤ √(Cαβ)
    Theorems 3.1 and 3.4; the clean delay law only holds when noise vanishes as αβ → 0; robustness to larger noise enters only through the C3∥ξ∥₂ terms in Theorems 3.3 and 3.5.
  • domain assumption Robust null space property / robust rank null space property of the measurement map
    Theorems 3.3 and 3.5 import Foucart-Rauhut compressed sensing guarantees; this is the formal content of the abstract's premise 'there exists a model with property P that generalizes'.
  • standard math Step-size and regularization bounds: 0 < ασmax(X⊤X) < 2, 0 < β√n < σmax(X⊤X)
    Convergence regime for the linear recurrences (Theorems 3.1, 3.4, Appendix C.4), standard gradient descent step-size conditions.

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Pith. "Pith review of Grokking Beyond the Euclidean Norm of Model Parameters." pith.science (2026). https://pith.science/paper/JUZYCOJ5

@misc{pith2026250605718,
  author       = {Pith},
  title        = {Pith review of: Grokking Beyond the Euclidean Norm of Model Parameters},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/JUZYCOJ5}},
  note         = {Machine review of arXiv:2506.05718}
}
abstract

Grokking refers to a delayed generalization following overfitting when optimizing artificial neural networks with gradient-based methods. In this work, we demonstrate that grokking can be induced by regularization, either explicit or implicit. More precisely, we show that when there exists a model with a property $P$ (e.g., sparse or low-rank weights) that generalizes on the problem of interest, gradient descent with a small but non-zero regularization of $P$ (e.g., $\ell_1$ or nuclear norm regularization) results in grokking. This extends previous work showing that small non-zero weight decay induces grokking. Moreover, our analysis shows that over-parameterization by adding depth makes it possible to grok or ungrok without explicitly using regularization, which is impossible in shallow cases. We further show that the $\ell_2$ norm is not a reliable proxy for generalization when the model is regularized toward a different property $P$, as the $\ell_2$ norm grows in many cases where no weight decay is used, but the model generalizes anyway. We also show that grokking can be amplified solely through data selection, with any other hyperparameter fixed.

Figures

Figures reproduced from arXiv: 2506.05718 by the authors.

Figure 1
Figure 1. (Top) Training and test accuracy of a MLP trained on modular addition with ℓ1 (left), ℓ2 (middle), and ℓ∗ (right) regularization for different values of the regulariza￾tion strength β. Smaller values of β delay generalization. (Bottom) In the case of ℓ1 (top-left), we show the evolution of the ℓ1 (left), ℓ2 (middle), and ℓ∗ (right) norm during train￾ing. The ℓ2 norm increases despite generalization. 0 10000 20000 St… view at source ↗
Figure 2
Figure 2. Training and test accuracy of a MLP trained on [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Relative errors, gradient ratio, norm of [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figures from the paper (31 more)
Figure 4
Figure 4. Figure 4: Generalization step t2 (smaller t such that ∥a (t) − a ∗∥2/∥a ∗∥2 ≤ 10−4 ) and recovery error ∥a (t2) − a ∗∥1 as a function of αβ. We can see that t2 ∝ ∥aˆ − a ∗∥∞/αβ and ∥a (t2) − a ∗∥1 ∝ αβ, i.e. small αβ require longer time to converge, but do so at a lower generali…
Figure 5
Figure 5. Figure 5: Relative errors, gradient ratio, the norm [PITH_FULL_IMAGE:figures/full_fig_p007_5.png]
Figure 6
Figure 6. Figure 6: Generalization step t2 (smaller t such that ∥A(t)− A∗∥F/∥A∗∥F ≤ 10−4 ) and recovery error ∥A(t2) − A∗∥2 as a function of αβ. We can see that t2 ∝ ∥Aˆ − A∗∥2→2/αβ and ∥A(t2) − A∗∥F ∝ αβ, i.e. small αβ require longer time to converge, but do so at a lower gen￾eralization…
Figure 8
Figure 8. Figure 8: Training and recovery error as a func￾tion of data size and co￾herence τ . Unlike matrix factorization, large values of coherence are detrimental to generalization for compressed sensing. The incoherence between the mea￾surement vectors (rows of M) and the sparse basis…
Figure 9
Figure 9. Figure 9: Recovery error as a function of depth and data size. We explore the role of overpa￾rameterization in sparse recovery using a linear network parame￾terized as a = ⊙L k=1Ak, where the depth L ≥ 2 introduces over￾parameterization without altering the linearity of the func…
Figure 11
Figure 11. Figure 11: Training and test error two layers ReLU teacher￾student with Sobolev training, for different values of the learning rate α and the Sobolev coefficient β. Classification On the algorithmic dataset (Power et al., 2022), ℓ1 and ℓ∗ have the same effect on grokking as ℓ2, …
Figure 10
Figure 10. Figure 10: Training and test error two layers ReLU teacher￾student with ℓ1 regularization, for different values of the learning rate α and the ℓ1 coefficient β. Domain Specific Regularization Physics-Informed Neu￾ral Networks (Raissi et al., 2019) leverage prior knowledge from d…
Figure 12
Figure 12. Figure 12: Sparse recovery with the projected subgradient descent method. [PITH_FULL_IMAGE:figures/full_fig_p046_12.png]
Figure 13
Figure 13. Figure 13: Sparse recovery with the soft-thresholding algorithm (ISTA) [PITH_FULL_IMAGE:figures/full_fig_p047_13.png]
Figure 14
Figure 14. Figure 14: Matrix sensing with the projected subgradient method. [PITH_FULL_IMAGE:figures/full_fig_p048_14.png]
Figure 15
Figure 15. Figure 15: Matrix sensing with the Proximal Gradient Descent method. [PITH_FULL_IMAGE:figures/full_fig_p048_15.png]
Figure 16
Figure 16. Figure 16: Relative errors and ∥a (t)∥1; with large initialization scale ζ = 101 and small weights decay β = 10−5 . Without visualization of the error on a logarithmic scale (left), it looks like grokking has occurred, whereas this is not the case (right). As shown in Section C.…
Figure 17
Figure 17. Figure 17: Training and recovery error as a function of the number of samples [PITH_FULL_IMAGE:figures/full_fig_p051_17.png]
Figure 18
Figure 18. Figure 18: Training and error ∥Xa(t1) − y ∗∥2/∥y ∗∥2 and recovery error ∥a (t2) − a ∗∥2/∥a ∗∥2 (along with t1 and t2, the memorization and the generalization step) as a function of the number of sample N and the depth L. The growth (as a function of N) in the test error for L = …
Figure 19
Figure 19. Figure 19: (a) Cohence µ(M⊤, Φ) as a function of τ ∈ (0, 1) (b) Minimum number of samples for perfect recovery (relative recovery error ≤ 10−6 ) for n = 102 as a function of the sparsity level s ∈ [n] and coherence parameter τ ∈ (0, 1) nN exp  − t 2 2σ2  . Using t = 2C2 √ ln(n…
Figure 20
Figure 20. Figure 20: Relative error ∥a − a ∗∥2/∥a ∗∥2 as a function of the number of measurements N, the sparsity level s ∈ [n] and and coherence parameter τ ∈ (0, 1), for n = 102 55 [PITH_FULL_IMAGE:figures/full_fig_p055_20.png]
Figure 21
Figure 21. Figure 21: Training and recovery error as a function of the number of samples [PITH_FULL_IMAGE:figures/full_fig_p057_21.png]
Figure 22
Figure 22. Figure 22: Training and error ∥Xa(t1) − y ∗∥2/∥y ∗∥2 and recovery error ∥a (t2) − a ∗∥2/∥a ∗∥2 (along with t1 and t2, the memorization and the generalization step) as a function of the number of sample N and the coherence parameter τ ∈ [0, 1]. constant, and C > 0 a universal con…
Figure 23
Figure 23. Figure 23: Training error ∥X vec A(t) − y ∗∥2/∥y ∗∥2 and recovery error ∥A(t) − A∗∥2/∥A∗∥F as a function of the number of sample N and the coherence parameter τ ∈ [0, 1] H. Additional Experiments H.1. Sparse Recovery Optimization landscape We look at the landscape of the solutio…
Figure 24
Figure 24. Figure 24: From initialization to least square solution [PITH_FULL_IMAGE:figures/full_fig_p061_24.png]
Figure 25
Figure 25. Figure 25: Convergence of a (t) i to a ∗ i for each i ∈ [n]. Here (n, s, N) = (100, 5, 30) and (α, β) = (10−1 , 10−5 ). 10 1 10 3 10 5 10 7 10 5 10 4 10 3 10 2 10 1 10 0 Error = 0.005 ||Xa (t) y * ||2 / ||y * ||2 ||a (t) a * ||2 / ||a * ||2 10 6 10 5 10 4 10 3 10 2 10 1 10 1 10 …
Figure 26
Figure 26. Figure 26: Training and recovery error as a function of the learning rate [PITH_FULL_IMAGE:figures/full_fig_p062_26.png]
Figure 27
Figure 27. Figure 27: Training and recovery error as a function of the sparsity level [PITH_FULL_IMAGE:figures/full_fig_p063_27.png]
Figure 28
Figure 28. Figure 28: Training error ∥Xa(t1) − y ∗∥2/∥y ∗∥2 at memorization, recovery error ∥a (t2) − a ∗∥2/∥a ∗∥2 at generalization, memorization step t1 (smaller t such that ∥Xa(t) − y ∗∥2/∥y ∗∥2 ≤ 10−4 ), and generalization step (smaller t such that ∥a (t) − a ∗∥2/∥a ∗∥2 ≤ 10−4 or the m…
Figure 29
Figure 29. Figure 29: Training and recovery error as a function of the learning rate [PITH_FULL_IMAGE:figures/full_fig_p064_29.png]
Figure 30
Figure 30. Figure 30: Training and test accuracy of a MLP trained on modular addition with [PITH_FULL_IMAGE:figures/full_fig_p064_30.png]
Figure 31
Figure 31. Figure 31: Training and test error two layers ReLU teacher-student with ℓ1 regularization, for different values of the learning rate α and the ℓ1 coefficient β. H.3.3. DOMAIN SPECIFIC REGULARIZATION Physics-Informed Neural Networks (Raissi et al., 2019) leverage prior knowledge …
Figure 32
Figure 32. Figure 32: Training and test error two layers ReLU teacher-student with ℓ2 regularization, for different values of the learning rate α and the ℓ2 coefficient β. 10 1 10 3 10 5 0.0 2.5 5.0 7.5 10.0 12.5 Loss = 0.0001 Train Test 10 7 10 6 10 5 10 4 10 3 10 2 10 1 10 1 10 3 10 5 0.…
Figure 33
Figure 33. Figure 33: Training and test error two layers ReLU teacher-student with ℓ∗ regularization, for different values of the learning rate α and the ℓ∗ coefficient β. 66 [PITH_FULL_IMAGE:figures/full_fig_p066_33.png]
Figure 34
Figure 34. Figure 34: Training and test error two layers ReLU teacher-student with Sobolev training, for different values of the learning rate α and the ℓ1 coefficient β. H.3.4. IMAGE CLASSIFICATION We optimize the parameters θ = (A, B) of a model yθ(x) = Bϕ(Ax) on N = 1000 samples of the …
Figure 35
Figure 35. Figure 35: Training and test accuracy of a MLP trained on MNIST with [PITH_FULL_IMAGE:figures/full_fig_p067_35.png]

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Works this paper leans on

31 extracted references · 26 canonical work pages

  1. [1]

    We also have ∥zy∥2 ≤ L since L = supy′∈B(x,r) supz∈∂h(y′) ∥z∥2

    If g(y) ̸= 04, then since y ∈ B(x, r) and g(y) ̸= 0, we have ∥∇g(y)∥2 2 ≥ g(y) · χ(g, x, r) from the CL constant for g. We also have ∥zy∥2 ≤ L since L = supy′∈B(x,r) supz∈∂h(y′) ∥z∥2. Using Cauchy–Schwarz: ⟨∇g(y), zy⟩ ≥ −∥∇g(y)∥2 · ∥zy∥2 ≥ −L∥∇g(y)∥2 (58) So ∥∇f (y)∥2 2 = ∥∇g(y)∥2 2 + 2β⟨∇g(y), zy⟩ + β2∥zy∥2 2 ≥ ∥∇g(y)∥2 2 + 2β⟨∇g(y), zy⟩ ≥ ∥∇g(y)∥2 2 − 2...

  2. [2]

    Then, for any η >0, mint1≤t≤t2 f (x(t)) − f ∗ ≤ (η+Cαβ )β 2 if and only if t2 ≥ t1 + R2 αβη

    Assume there exists a constant C >0, L ≤ Cβ 2. Then, for any η >0, mint1≤t≤t2 f (x(t)) − f ∗ ≤ (η+Cαβ )β 2 if and only if t2 ≥ t1 + R2 αβη . Moreover, if Assumptions C.5 holds, then mint1≤t≤t2 h(x(t)) − h∗ g ≤ η+Cαβ 2 if and only if t2 ≥ t1 + R2 αβη . Proof. Using maxt1≤t≤t2 ∥F (x(t))∥2 2 ≤ maxt1≤t ∥F (x(t))∥2 2 = L ≤ Cβ 2, we derive the following from Le...

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    In particular, for h(a) = sign(a) ∀a ∈ R, if a(1)/α ∈ Z, then a(t) = 0 for all t >⌊ |a(1)| α ⌋. Proof. Let first consider the simple case H(a) = sign(a), so that a(t+1) = a(t) − α sign(a(t)). • If a(t) ∈ {0, α,−α}, then a(t+∆) = 0 for all ∆ > 0. • If a(t) ∈ (0, α), then a(t+1) = a(t) − α ∈ (−α, 0), and a(t+2) = a(t+1) + α = a(t) ∈ (0, α), and so on. • If ...

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    Then for all 0 ≤ j ≤ k − 1, |Rj| ≤ ϵα∥∇g(x(j))∥2 2 if α ≤ 2(ϵ − γ)/L2p (ϵ + γ)α∥∇g(x(j))∥2 2 if α ≤ 2ϵ/L2p (37) Proof

    Suppose that x(j) ∈ B(x(0), r) and β supH∈∂h(x(j)) ∥H∥2 ≤ γ∥G(x(j))∥2 for all 0 ≤ j ≤ k − 1, for some k ≥ 1. Then for all 0 ≤ j ≤ k − 1, |Rj| ≤ ϵα∥∇g(x(j))∥2 2 if α ≤ 2(ϵ − γ)/L2p (ϵ + γ)α∥∇g(x(j))∥2 2 if α ≤ 2ϵ/L2p (37) Proof. Let Sj := g(x(j+1)) − g(x(j)) + αG(x(j))⊤(G(x(j)) + βH (x(j))) = Rj + αβG(x(j))⊤H(x(j)). Fix j ≤ k − 1 and let x(t) := x(j) − tα ...

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    So ∥∇f (y)∥2 2 f (y) ≥ β ∥zy∥2 2 h(y) ≥ βχ(h, x, r′)

    If g(y) = 0 , then f (y) = βh(y) ̸= 0 and zy ̸= 0 (since 0 ∈ ∂h(y) =⇒ h(y) = 0 ). So ∥∇f (y)∥2 2 f (y) ≥ β ∥zy∥2 2 h(y) ≥ βχ(h, x, r′). Plugging χ(f, x, r′) ≥ βχ(h, x, r′) into the CL inequality: 4f (x) = 4g(x) + 4βh(x) < r′2β · χ(h, x, r′) ≤ r′2 · χ(f, x, r′) ⇐ ⇒4g(x) < r′2 · χ(h, x, r′) − 4h(x) β with r′2 · χ(h, x, r′) − 4h(x) > 0 ⇐ ⇒ 4g(x) r′2 · χ(h, x...

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    Theorem C.29

    Later in training, H(a) dominates the update, leading to ∥a(t)∥1 ≈ ∥a∗∥1. Theorem C.29. Assume the learning rate, the regularization coefficent and the noise satisfy 0 < α < αmax := 2 σmax(X⊤X), 0 < β <σmax(X⊤X)√n and ∥X⊤ξ∥2 ≤ √ Cαβ , C >0. Let ρ2 := σmax In − αX⊤X . There exist t1 < ∞ and a constant C ′ > 0 such that: ∥a(t) − ˆa∥2 ≤ 2αβn1/2 1 − ρ2 and g(...

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    g(ˆa) − 1 2 ∥ξ∥2 2 = − 1 2 ξ⊤UU⊤ξ = − 1 2 ∥U⊤ξ∥2

    We have ˆa = X⊤X † X⊤y∗ = VΣ−1V⊤VΣ 1 2 U⊤ UΣ 1 2 V⊤a∗ + ξ = VV⊤a∗ + VΣ− 1 2 U⊤ξ (70) So Xˆa − y∗ = UΣ 1 2 V⊤VV⊤a∗ + UΣ 1 2 V⊤VΣ− 1 2 U⊤ξ − UΣ 1 2 V⊤a∗ − ξ = (IN − UU⊤)ξ (71) and ∥Xˆa − y∗∥2 2 = ξ⊤(IN − UU⊤)(IN − UU⊤)ξ = ξ⊤(IN − UU⊤)ξ ≤ ∥ξ∥2 2 (72) i.e. g(ˆa) − 1 2 ∥ξ∥2 2 = − 1...

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    This implies, assuming E[ξ] = 0 and Cov(ξ) = σ2 ξ IN , 2Eξg(ˆa) = Eξ∥Xˆa − y∗∥2 2 = Eξ∥(IN − UU⊤)y∗∥2 2 = Eξ h ξ⊤(IN − UU⊤)ξ i = tr (IN − UU⊤) Cov(ξ) + (Eξ)⊤ (IN − UU⊤) (Eξ) = σ2 ξ tr IN − UU⊤ = σ2 ξ (N − r) (73) Since ˆa − a∗ = X⊤X † X⊤y∗ − a∗ = V V⊤a∗ + Σ− 1 2 U⊤ξ − a∗ = (In...

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    We also have Θf = {a∗} and Θg = {a | X(a − a∗) = ξ}. Applying Lemma C.12, we get min t1≤t≤t2 f (a(t)) − f (a∗) ≤ ∥a(t1) − a∗∥2 2 + (t2 − t1)α2 maxt1≤t≤t2 ∥F (a(t))∥2 2 2α(t2 − t1) ∀t2 ≥ t1 (87) Using ∥F (a(t))∥2 = O (β) ∀t ≥ t1 (Equation (84)) we get from Theorem C.13 that the...

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    A point a is stationary for this dynamical system if and only if |a| ≤α. 37 Grokking Beyond the Euclidean Norm of Model Parameters

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    In particular, for h(a) = sign(a) ∀a ∈ Rn, we have ∥a(t)∥0 = n i | a(1) i /α ∈ Z o for all t >⌊ ∥a(1)∥∞ α ⌋. Proof. The proof is immediate by applying the Lemma C.30 coordinate-wise. Lemma C.32. Let a, a∗ ∈ R with a ̸= 0. If |a| > |a∗|, then sign(a − a∗) = sign(a). Proof. We h...

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    We write F (A) := G(A) + βH (A) with vec G(A) := ∇ag(A) = X⊤Xa − X⊤Xa∗ + X⊤ξ and H(A) ∈ ∂∥A∥∗ = {UV⊤ +W, ∥W∥2→2 ≤ 1, U⊤W = 0, WV = 0} any subgradient of ∥A∥∗, with A = UΣV⊤ under the compact SVD7 8 . Suppose we start at some A(1). Using F(t) := F (A(t)), the subgradient update...

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    Let Q := X⊤X + βIn. We have f (a) := 1 2 ∥y(a) − y∗∥2 2 + β 2 ∥a∥2 2 = 1 2 a⊤Qa − X⊤Xa∗ + X⊤ξ ⊤ a + 1 2 ∥Xa∗ + ξ∥2 2 (110) and F (a) := ∇af (a) = X⊤(y − y∗) + βa = Qa − X⊤Xa∗ + X⊤ξ (111) The subgradient update rule is a(t+1) = a(t) − αF (a(t)) = (In − αQ) a(t) + α X⊤Xa∗ + X⊤ξ ...

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    In particular, if a∗ has a nonzero component orthogonal to the column space of V, then ˆa cannot perfectly generalize to a∗. Proof. In Lemma C.52, we show that ∥a(t+1) − ˆa∥p ≤ ρt p∥a(1) − ˆa∥p ∀t ≥ 0. So for t ≥ ln η/∥a(1) − ˆa∥p / ln ρp, we have ∥a(t+1) − ˆa∥p ≤ η. Consider ...

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Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.