REVIEW 2 major objections 4 minor 1 cited by
Fast convex optimization via inertial systems with asymptotically vanishing viscosity and Hessian-driven damping
T0 review · 2 major / 4 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read With $r=\alpha\beta$ and $\dot x(0)=-\beta\nabla f(x_0)$, Polyak–Lojasiewicz gives $e^{-2\mu\beta t}$ decay followed by $O(t^{-2\alpha})$ for every $\alpha>0$, and linear rates under strong convexity.
desk verdict Solid theoretical extension of Nesterov-rate analysis: new o(1/t^{2α}) and linear rates for subcritical α under PL, with the main caveat being well-posedness assumptions that are referenced but not stated. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the time-dependent energy function $\varepsilon(t)=\frac{1}{2}\|\dot x+\beta\nabla f(x)\|^2+\frac{\omega}{2}\|\dot x\|^2+\theta(f(x)-f^*)$, with parameters chosen as $r=\alpha\beta/(1+\omega)$ and $\theta=(1+\omega)\gamma-\omega\eta\beta^2/(1+\omega)$. Setting $\omega=0,\eta=\mu$ makes its derivative obey $\dot\varepsilon\le -2\min\{\alpha/t,\mu\beta\}\varepsilon$, which integrates to the exponential-fast-then-polynomial envelope; setting $\omega=1,\eta=\mu$ gives $\dot\varepsilon\le-(2\alpha/t+\mu\beta/2)\varepsilon$, which yields the strong-convexity linear rate. The same idea drives the discrete proofs through the energy sequence $E_k=\frac{1}{2}\|v_k+h\nabla f(x_k)\|^2+\gamma[(1-\omega)\psi_k+\omega(f(y_{k+1})-f^*)]$ and its proximal analogue. These identities are what transfer the rate information from the Hessian-damped flow to the algorithms.
What would settle it
Fix $\alpha,\beta,\gamma>0$ with $r=\alpha\beta$, choose a twice differentiable convex $f$ satisfying the Polyak–Lojasiewicz inequality with known $\mu$ (for example $f(x)=\frac{1}{2}x^2$ with $\mu=L=1$), set $\dot x(0)=-\beta f'(x_0)$, and integrate (AVD-H) numerically. The theorem is settled if the value gap ever exceeds the claimed envelope $e^{-2\mu\beta t}(f(x_0)-f^*)$ on $t\le \alpha/(\mu\beta)$, if $t^{2\alpha}(f(x(t))-f^*)$ fails to tend to $0$, or if any admissible $f$ yields no global solution.
Extended reading notes
Core claim
On the paper's own terms, the central discovery is a two-phase function-value estimate for trajectories of the inertial system (AVD-H). For a twice differentiable $f$ satisfying the Polyak–Lojasiewicz inequality $\|\nabla f(x)\|^2\ge 2\mu(f(x)-f^*)$, with $\alpha,\beta,\gamma>0$, $r=\alpha\beta$, and $\dot x(0)=-\beta\nabla f(x_0)$, the bound is $f(x(t))-f^*\le (f(x_0)-f^*)e^{-2\mu\beta t}$ for $t\le \alpha/(\mu\beta)$, and $f(x(t))-f^*\le (f(x_0)-f^*)(\alpha/(\mu\beta e))^{2\alpha}t^{-2\alpha}$ afterwards; convexity upgrades the tail to $o(t^{-2\alpha})$. For $\mu$-strongly convex $f$, the system satisfies $f(x(t))-f^*\le e^{-\frac{1}{2}\mu\beta(t-T)}/(t/T)^{2\alpha}C_T$ for $t\ge T=4\alpha/(\mu\beta)+4\alpha\beta/(4\gamma-\mu\beta^2)$, provided $\gamma>\frac{1}{4}\mu\beta^2$ and $r=\frac{1}{2}\alpha\beta$. The discrete companion (AGM) reproduces the same linear-then-$O(k^{-2\alpha})$ envelope, with $o(k^{-2\alpha})$ under convexity, and the proximal scheme (APM) achieves linear convergence under strong convexity. The message is that Hessian-driven damping, rather than a large $\alpha$, is what removes the obstacle to fast convergence in this family.
Load-bearing premise
The whole rate picture assumes that the differential equation (AVD-H) always has a unique global solution for every twice differentiable objective whose gradient is $L$-Lipschitz; the paper cites prior work for this rather than proving it, so a finite-time blow-up of any admissible trajectory would leave the rates without meaning.
Editorial extensions
If this is right
- For any $\alpha>0$, the continuous dynamics (AVD-H) reaches $O(t^{-2\alpha})$ under Polyak–Lojasiewicz, with the exponential $e^{-2\mu\beta t}$ phase ending at $t=\alpha/(\mu\beta)$.
- Hessian-driven damping removes the strong-convexity obstruction: a linear rate proportional to $e^{-\frac{1}{2}\mu\beta t}$ (up to a polynomial factor) holds, whereas the undamped system $\ddot x+\frac{\alpha}{t}\dot x+\nabla f(x)=0$ cannot converge linearly even for strongly convex $f$.
- The discretization (AGM) inherits the two-phase structure: the value gap stays within $O((1+\mu h^2(2-\gamma))^{-k})$ until an explicit index $K$, then within $O(k^{-2\alpha})$, and vanishes as $o(k^{-2\alpha})$ for convex $f$.
- The proximal algorithm (APM) for composite problems $f+g$ satisfies the same sublinear $O(k^{-2\alpha})$ under Polyak–Lojasiewicz and a linear rate $(1+\rho)^{-k}$ with $\rho=\mu\min\{s/2,\,s(1-sL)/(1+\mu L s^2)\}$ when $f$ is strongly convex.
- With the exact initial velocity, the damping coefficient $\gamma$ drops out of the rate constants in the continuous theorem, so $\gamma$ can be tuned freely to control oscillation without changing the order of convergence.
Reading between the lines
- Editorial extension: the paper fixes the initial velocity to $-\beta\nabla f(x_0)$ exactly; the energy argument indicates that any nonzero initial error $\dot x(0)+\beta\nabla f(x_0)$ should weaken the exponential phase, and a quantitative perturbation bound would make this precise.
- Editorial extension: because the switch time $\alpha/(\mu\beta)$ is explicit, the natural algorithmic corollary is a restart schedule near that threshold, although the paper itself does not study restarts.
- Editorial extension: since $\gamma$ does not affect the rates under the exact initial condition, one can treat $\gamma$ as an oscillation-suppression dial and test numerically whether larger $\gamma$ smooths trajectories without losing the envelope.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies the inertial differential system (AVD-H) combining asymptotic vanishing viscosity, Hessian-driven damping, and a time-dependent gradient coefficient. The main continuous-time results are Lyapunov-energy estimates giving, under a Polyak-Łojasiewicz inequality, a function-value gap that decays like e^{-2μβt} for t ≤ α/(μβ) and like O(t^{-2α}) afterward, with an o(t^{-2α}) improvement under additional convexity; for strongly convex objectives the paper proves a rate of the form O(t^{-2α}e^{-μβt/2}). The paper then discretizes the system into an accelerated gradient algorithm (AGM) and an accelerated proximal-gradient algorithm (APM), proving analogous O(k^{-2α})/o(k^{-2α}) rates under convexity plus PL, and linear rates under strong convexity.
Significance. The claimed rates are substantially faster than the previously known O(t^{-2α/3}) for this class of inertial systems, and they are obtained for all α>0 rather than only for α≥3. The proofs are based on explicit Lyapunov energies with no fitted parameters, which is a genuine strength, and the extension to proximal-gradient algorithms broadens the applicability. If the well-posedness and smoothness-assumption gaps identified below are closed, the continuous-time results would constitute a clear advance over the existing literature and give useful insight into Nesterov acceleration. The discrete-time results are also interesting, although the improvements there are more incremental relative to known O(k^{-2}) and o(k^{-2α}) bounds.
major comments (2)
- [Section 1, after (AVD-H); Theorems 2.2 and 2.5] The paper assumes global existence and uniqueness of C^2 solutions of (AVD-H) for the full parameter range, referring only to 'the discussion in [17]'. This assumption is load-bearing because every rate in Section 2 is stated pointwise for all t>0, and the proof of Theorem 2.2 evaluates the energy at t=0 (ε(0)) and integrates the differential inequality from there. The manuscript does not identify which result in [17] applies, nor does it verify that the hypotheses of that result cover the scope of Theorem 2.2, which explicitly allows nonconvex PL functions and all α>0. Please state the exact existence theorem, verify that its assumptions (e.g., convexity, L-smoothness, or lower bounds on α) are satisfied in the nonconvex PL setting, or add the necessary hypotheses and state the rates for t≥t0 with a local-existence argument. Without this, the claimed rates are conditional on an unverified well-posedness assertion.
- [Theorem 2.2, proof of o(1/t^{2α})] The proof of the o(1/t^{2α}) statement invokes the inequality (1/(2L))∥∇f(x)∥^2 ≤ f(x)-f*, which is a consequence of L-smoothness. However, the theorem statement assumes only that f is twice differentiable and satisfies the PL inequality, plus convexity for the o part. Convexity alone does not imply L-smoothness, so as stated the proof has a gap. Either add L-smoothness to the hypotheses of Theorem 2.2 (if it is intended as a standing assumption of Section 1, make that explicit in the theorem), or provide a proof of the o bound that does not use this inequality.
minor comments (4)
- [Proposition 4.3] In the displayed formula for E_{k+1}-E_k, the term ∥x_{k+1}-x_{k+1}∥^2 should read ∥x_{k+1}-y_{k+1}∥^2, as is clear from the preceding derivation using (4.2).
- [Theorems 3.3 and 4.4] The definitions of K are off by one relative to the range where the linear-contraction term is active: in Theorem 3.3 the condition should be applied to k+1 rather than k, and in Theorem 4.4 similarly. The asymptotic rates are unchanged, but the constants (K-1 or K) should be shifted consistently.
- [Remark 2.6] The condition '0<β<2√μ' appears inconsistent with Theorem 2.5, which for γ=1 requires β<2/√μ. Please correct this condition.
- [Theorem 2.5] The statement does not specify the initial condition v0 or clarify how the trajectory is assumed to exist up to the time T; please state the existence assumption explicitly so that the bound for t≥T is unambiguous.
Circularity Check
No circularity: the rates follow from explicit energy inequalities; the cited existence result [17] is a side condition and not used to force the rate.
full rationale
The derivation chain is self-contained. For the continuous system, Proposition 2.1 computes the derivative of the energy (2.1) by direct algebra from (AVD-H) with r = alpha*beta/(1+omega), and Theorem 2.2 then substitutes omega = 0, eta = mu, and integrates the resulting differential inequality. The rate exponent 2*mu*beta is a consequence of the Polyak-Lojasiewicz input, not an assumption encoded in the energy: the energy only contains the terms needed to make the derivative calculation close. The initial condition v0 = -beta grad f(x0) merely makes epsilon(0) equal to gamma(f(x0)-f*), which is an initialization choice rather than a fitted parameter. The discrete results in Sections 3 and 4 follow the same pattern: the energy sequences are defined explicitly, their differences are computed from the algorithm recursions, and the cited Lemma 4.1 from [9] is an external one-step descent lemma, not a restatement of the target rate. The only self-citation is the existence and uniqueness discussion in [17]; this supports well-posedness of the ODE but is not used to derive the value decay, and no reduction of the main rates to [17] is exhibited. Thus there is no significant circularity.
Assumptions & free parameters
free parameters (4)
- α
- β
- γ
- r =
αβ (PL case), αβ/2 (strongly convex case)
assumptions (5)
- domain assumption Global existence and uniqueness of solutions to (AVD-H) for twice differentiable f with L-Lipschitz gradient
- domain assumption PL inequality: ||∇f(x)||² ≥ 2μ(f(x)-f*)
- domain assumption Strong convexity: f(y) ≥ f(x) + ⟨∇f(x),y-x⟩ + μ/2||y-x||²
- standard math L-smoothness: f(y) ≤ f(x) + ⟨∇f(x),y-x⟩ + L/2||y-x||²
- standard math Lemma 4.1 from [9]
Cite this review
Pith. "Pith review of Fast convex optimization via inertial systems with asymptotically vanishing viscosity and Hessian-driven damping." pith.science (2026). https://pith.science/paper/ENBWYKYK
@misc{pith2026250621730,
author = {Pith},
title = {Pith review of: Fast convex optimization via inertial systems with asymptotically vanishing viscosity and Hessian-driven damping},
year = {2026},
howpublished = {\url{https://pith.science/paper/ENBWYKYK}},
note = {Machine review of arXiv:2506.21730}
}
read the original abstract
We study the convergence rate of a family of inertial algorithms, which can be obtained by discretization of an inertial system combining asymptotic vanishing viscous and Hessian-driven damping. We establish a fast sublinear convergence rate in case the objective function is convex and satisfies Polyak-\L ojasiewicz inequality. We also establish a linear convergence rate for strongly convex functions. The results can provide more insights into the convergence property of Nesterov's accelerated gradient method.
Forward citations
Cited by 1 Pith paper
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Inertial Primal Dual Dynamics with Hessian-driven Damping for Saddle Point Problems
New inertial primal-dual ODEs with Hessian damping achieve O(1/t²) convex rates and O(1/t^{α−1}) strongly-convex rates without knowing the strong convexity moduli.
Reference graph
Works this paper leans on
-
[17]
J. J. Maul´en and J. Peypouquet, A speed restart scheme for a dynamics with Hessian-driven damping, Journal of Optimization Theory and Applications, 199 (2023), pp. 831–855
work page 2023
-
[3]
H. Attouch, Z. Chbani, J. F adili, and H. Riahi , First-order optimization algorithms via inertial systems with Hessian driven damping , Mathematical Programming, 193 (2022), pp. 113–155
work page 2022
-
[1]
V. Apidopoulos, J.-F. Aujol, and C. Dossal, Convergence rate of inertial forward–backward algorithm beyond Nesterov’s rule , Mathematical Programming, 180 (2020), p. 137–156
work page 2020
-
[2]
V. Apidopoulos, J.-F. Aujol, C. Dossal, and A. Rondepierre , Convergence rates of an inertial gradient descent algorithm under growth and flatness conditions , Mathematical Programming, 187 (2021), pp. 151–193
work page 2021
-
[4]
H. Attouch, Z. Chbani, J. Peypouquet, and P. Redont , Fast convergence of inertial dy- namics and algorithms with asymptotic vanishing viscosity , Mathematical Programming, 168 (2018), pp. 123–175
work page 2018
-
[5]
H. Attouch, Z. Chbani, and H. Riahi , Rate of convergence of the Nesterov accelerated gra- dient method in the subcritical case α ≤ 3, ESAIM: Control, Optimisation and Calculus of Variations, 25 (2019)
work page 2019
-
[6]
H. Attouch and J. Peypouquet , The rate of convergence of Nesterov’s accelerated forward- backward method is actually faster than 1/k2, SIAM Journal on Optimization, 26 (2016), pp. 1824–1834
work page 2016
-
[7]
H. Attouch, J. Peypouquet, and P. Redont, Fast convex optimization via inertial dynamics with Hessian driven damping, Journal of Differential Equations, 261 (2016), pp. 5734–5783
work page 2016
Show all 22 references
-
[8]
Aujol, C
J.-F. Aujol, C. Dossal, and A. Rondepierre , Optimal convergence rates for Nesterov accel- eration, SIAM Journal on Optimization, 29 (2019), pp. 3131–3153
2019
-
[9]
C. Bao, L. Chen, and J. Li, The global R-linear convergence of Nesterov’s accelerated gradient method with unknown strongly convex parameter , arXiv:2308.14080v2, (2023)
2023 arXiv
-
[10]
Beck and M
A. Beck and M. Teboulle, A fast iterative shrinkage-thresholding algorithm for linear inverse problems, SIAM Journal on Imaging Sciences, 2 (2009), pp. 183–202
2009
-
[11]
fast iterative shrink- age/thresholding algorithm
A. Chambolle and C. Dossal, On the convergence of the iterates of the “fast iterative shrink- age/thresholding algorithm”, Journal of Optimization Theory and Applications, 166 (2015), pp. 968–982
2015
-
[12]
Drori and M
Y. Drori and M. Teboulle, Performance of first-order methods for smooth convex minimiza- tion: a novel approach , Mathematical Programming, 145 (2014), pp. 451–482
2014
-
[13]
Kim and J
D. Kim and J. Fessler, Optimized first-order methods for smooth convex minimization, Math- ematical Programming, 159 (2016), pp. 81–107
2016
-
[14]
Kim and J
D. Kim and J. Fessler, On the convergence analysis of the optimized gradient method, Journal of Optimization Theory and Applications, 172 (2017), pp. 187–205
2017
-
[15]
B. Li, B. Shi, and Y. Yuan , Linear convergence of forward-backward accelerated algorithms without knowledge of the modulus of strong convexity , SIAM Journal on Optimization, 34 (2024), pp. 2150–2168
2024
-
[16]
H. Liu, T. W ang, and Z. Liu , Convergence rate of inertial forward–backward algorithms based on the local error bound condition , IMA Journal of Numerical Analysis, 44 (2024), pp. 1003–1028
2024
-
[18]
May, Asymptotic for a second-order evolution equation with convex potential and vanishing damping term , Turkish Journal of Mathematics, 41 (2017), pp
R. May, Asymptotic for a second-order evolution equation with convex potential and vanishing damping term , Turkish Journal of Mathematics, 41 (2017), pp. 681–685
2017
-
[19]
Nesterov, A method for solving the convex programming problem with convergence rate O 1 k2 , Soviet Mathematics Doklady, 27 (1983), pp
Y. Nesterov, A method for solving the convex programming problem with convergence rate O 1 k2 , Soviet Mathematics Doklady, 27 (1983), pp. 372–376. 17
1983
-
[20]
C. Park, J. Park, and E. Ryu , Factor- √ 2 acceleration of accelerated gradient methods, Ap- plied Mathematics & Optimization, 88 (2023)
2023
-
[21]
B. Shi, S. Du, M. Jordan, and W. Su , Understanding the acceleration phenomenon via high- resolution differential equations, Mathematical Programming, 195 (2022), pp. 79–148
2022
-
[22]
W. Su, S. Boyd, and E. J. Cand`es, A differential equation for modeling Nesterov’s accelerated gradient method: Theory and insights , Journal of Machine Learning Research, 17 (2016), pp. 1–43. 18
2016
Reviewed August 6, 2026 · model on record in the stance chip above.
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