Research map / Learning theory and algorithms / Matrix and tensor methods
GL-LowPopArt: A Nearly Instance-Wise Minimax-Optimal Estimator for Generalized Low-Rank Trace Regression
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Proposes GL-LowPopArt, a two-stage nuclear-norm-regularized MLE plus matrix Catoni estimator for generalized low-rank trace regression, with an instance-wise error bound via a new GL-design objective, a local minimax lower bound, and an application to bilinear dueling bandits.
Problem
Estimating a low-rank matrix parameter from nonlinear (GLM) observations with matrix-valued covariates, where existing guarantees depend on worst-case curvature of the inverse link function rather than instance-specific curvature.
Approach
Two-stage estimator: nuclear-norm penalized MLE for a warm start, then a generalized linear matrix Catoni estimator using one-sample estimators debiased with the Hessian at the initial estimate, followed by singular value thresholding. Introduces the GL-Design objective, whose optimization yields instance-dependent error bounds and near-optimal lower bounds.
Key results
- Instance-wise error bound for GL-LowPopArt scaling with the GL-design objective, improving over worst-case curvature bounds in generalized linear matrix completion (1/min_ij mu-dot((Theta*)_ij) instead of 1/min over |z|<=gamma).
- A local minimax lower bound scaling with lambda_max of the Hessian, making GL-LowPopArt nearly instance-wise optimal up to the Hessian condition number for single-switch policies.
- Bilinear dueling bandit explore-then-commit algorithm attains Borda regret of order (GL_min)^{1/3}(kappa T)^{2/3} up to logs.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use GL-LowPopArt with optimal GL-design instead of the nuclear penalized MLE | Generalized low-rank trace regression · Frobenius and operator-norm unit balls | squared Frobenius error bound: \kappa_\star^{-2} d_1 d_2 (d_1 \wedge d_2) \gE(N) -> \kappa_\star^{-1} (d_1 \wedge d_2) \gE(N); \kappa_\star^{-2} (d_1 \ | Helped |
| Use GL-LowPopArt with optimal GL-design instead of the Stein estimator | Generalized low-rank trace regression · Frobenius and operator-norm unit balls | squared Frobenius error bound: \kappa_\star^{-2} (d_1 \wedge d_2) \gE(N) -> \kappa_\star^{-1} (d_1 \wedge d_2) \gE(N); \kappa_\star^{-2} (d_1 \vee d_2) | Helped |
| Adapt the curvature factor to the instance rather than the worst-case entrywise domain | GL-LowPopArt for 1-bit matrix completion · 1-bit matrix completion, uniform sampling | squared Frobenius error bound: \frac{1}{\min_{i,j} \dot{\mu}((\bm\Theta_\star)_{ij})} \frac{r d_1 d_2 (d_1 \vee d_2)}{N} | Helped |
| Use optimal GL-design instead of uniform sampling | GL-LowPopArt for 1-bit matrix completion · 1-bit matrix completion | squared Frobenius error bound: \mathrm{Harm}(\bm\Theta_\star)^{-1} \frac{r d_1 d_2 (d_1 \vee d_2)}{N} | Helped |
| Use GL-LowPopArt for the exploration phase and commit to the estimated Borda winner | BETC-GLM-LR · Bilinear dueling bandits | Borda regret: \left( \mathrm{GL}_{\min}(\gX) \log\frac{d}{\delta} \right)^{1/3} \left( \kappa_\star^B T \right)^{2/3} | Helped |
Limitations
- Analysis relies on covariates being bounded in operator norm (unbounded case left for future work).
- Requires the initial estimate to be sufficiently accurate, with a sample-size condition on Stage I.
- Lower bound is local and holds for single-switch policies only up to condition number; not matched for entrywise-constrained neighborhoods in matrix completion.
Experimental setup
Metrics: squared Frobenius error operator norm error Borda regret
Baselines: nuclear penalized MLE Stein estimator Dav14 1-bit matrix completion bound Klo15 bound Warm-LowPopArt
Builds on: LowPopArt Catoni estimator self-concordant generalized linear bandits
Closest papers by meaning
- Efficient Low-Rank Matrix Estimation, Experimental Design, and Arm-Set-Dependent Low-Rank Bandits (ICML 2024 · similarity 0.89)
- Flat Minima in Linear Estimation and an Extended Gauss Markov Theorem (ICLR 2024 · similarity 0.84)
- Robust Sparse Regression with Non-Isotropic Designs (NeurIPS 2024 · similarity 0.84)
- Low-Rank Bandits via Tight Two-to-Infinity Singular Subspace Recovery (ICML 2024 · similarity 0.83)
- Symmetric Matrix Completion with ReLU Sampling (ICML 2024 · similarity 0.83)
- A Unified Confidence Sequence for Generalized Linear Models, with Applications to Bandits (NeurIPS 2024 · similarity 0.83)
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