Search Results for author: Cong Ma

Found 45 papers, 9 papers with code

Batched Nonparametric Contextual Bandits

no code implementations27 Feb 2024 Rong Jiang, Cong Ma

We study nonparametric contextual bandits under batch constraints, where the expected reward for each action is modeled as a smooth function of covariates, and the policy updates are made at the end of each batch of observations.

Multi-Armed Bandits

Top-$K$ ranking with a monotone adversary

no code implementations12 Feb 2024 Yuepeng Yang, Antares Chen, Lorenzo Orecchia, Cong Ma

On the analytical front, we provide a refined $\ell_\infty$ error analysis of the weighted MLE that is more explicit and tighter than existing analyses.

On the design-dependent suboptimality of the Lasso

1 code implementation1 Feb 2024 Reese Pathak, Cong Ma

This paper investigates the effect of the design matrix on the ability (or inability) to estimate a sparse parameter in linear regression.

regression

Maximum Likelihood Estimation is All You Need for Well-Specified Covariate Shift

no code implementations27 Nov 2023 Jiawei Ge, Shange Tang, Jianqing Fan, Cong Ma, Chi Jin

This paper addresses this fundamental question by proving that, surprisingly, classical Maximum Likelihood Estimation (MLE) purely using source data (without any modification) achieves the minimax optimality for covariate shift under the well-specified setting.

regression Retrieval

Provably Accelerating Ill-Conditioned Low-rank Estimation via Scaled Gradient Descent, Even with Overparameterization

no code implementations9 Oct 2023 Cong Ma, Xingyu Xu, Tian Tong, Yuejie Chi

Many problems encountered in science and engineering can be formulated as estimating a low-rank object (e. g., matrices and tensors) from incomplete, and possibly corrupted, linear measurements.

Object

Unraveling Projection Heads in Contrastive Learning: Insights from Expansion and Shrinkage

no code implementations6 Jun 2023 Yu Gui, Cong Ma, Yiqiao Zhong

Firstly, through empirical and theoretical analysis, we identify two crucial effects -- expansion and shrinkage -- induced by the contrastive loss on the projectors.

Contrastive Learning

Sharp high-probability sample complexities for policy evaluation with linear function approximation

no code implementations30 May 2023 Gen Li, Weichen Wu, Yuejie Chi, Cong Ma, Alessandro Rinaldo, Yuting Wei

This paper is concerned with the problem of policy evaluation with linear function approximation in discounted infinite horizon Markov decision processes.

Multi-Teacher Knowledge Distillation For Text Image Machine Translation

no code implementations9 May 2023 Cong Ma, Yaping Zhang, Mei Tu, Yang Zhao, Yu Zhou, Chengqing Zong

Text image machine translation (TIMT) has been widely used in various real-world applications, which translates source language texts in images into another target language sentence.

Knowledge Distillation Machine Translation +2

E2TIMT: Efficient and Effective Modal Adapter for Text Image Machine Translation

1 code implementation9 May 2023 Cong Ma, Yaping Zhang, Mei Tu, Yang Zhao, Yu Zhou, Chengqing Zong

Furthermore, the ablation studies verify the generalization of our method, where the proposed modal adapter is effective to bridge various OCR and MT models.

Machine Translation Optical Character Recognition +2

The Power of Preconditioning in Overparameterized Low-Rank Matrix Sensing

no code implementations2 Feb 2023 Xingyu Xu, Yandi Shen, Yuejie Chi, Cong Ma

We propose $\textsf{ScaledGD($\lambda$)}$, a preconditioned gradient descent method to tackle the low-rank matrix sensing problem when the true rank is unknown, and when the matrix is possibly ill-conditioned.

Improving End-to-End Text Image Translation From the Auxiliary Text Translation Task

1 code implementation8 Oct 2022 Cong Ma, Yaping Zhang, Mei Tu, Xu Han, Linghui Wu, Yang Zhao, Yu Zhou

End-to-end text image translation (TIT), which aims at translating the source language embedded in images to the target language, has attracted intensive attention in recent research.

Multi-Task Learning Translation

$O(T^{-1})$ Convergence of Optimistic-Follow-the-Regularized-Leader in Two-Player Zero-Sum Markov Games

no code implementations26 Sep 2022 Yuepeng Yang, Cong Ma

We prove that optimistic-follow-the-regularized-leader (OFTRL), together with smooth value updates, finds an $O(T^{-1})$-approximate Nash equilibrium in $T$ iterations for two-player zero-sum Markov games with full information.

Fast and Provable Tensor Robust Principal Component Analysis via Scaled Gradient Descent

1 code implementation18 Jun 2022 Harry Dong, Tian Tong, Cong Ma, Yuejie Chi

An increasing number of data science and machine learning problems rely on computation with tensors, which better capture the multi-way relationships and interactions of data than matrices.

Pessimism for Offline Linear Contextual Bandits using $\ell_p$ Confidence Sets

no code implementations21 May 2022 Gene Li, Cong Ma, Nathan Srebro

We present a family $\{\hat{\pi}\}_{p\ge 1}$ of pessimistic learning rules for offline learning of linear contextual bandits, relying on confidence sets with respect to different $\ell_p$ norms, where $\hat{\pi}_2$ corresponds to Bellman-consistent pessimism (BCP), while $\hat{\pi}_\infty$ is a novel generalization of lower confidence bound (LCB) to the linear setting.

Multi-Armed Bandits

Optimally tackling covariate shift in RKHS-based nonparametric regression

no code implementations6 May 2022 Cong Ma, Reese Pathak, Martin J. Wainwright

We study the covariate shift problem in the context of nonparametric regression over a reproducing kernel Hilbert space (RKHS).

regression

Jump-Start Reinforcement Learning

no code implementations5 Apr 2022 Ikechukwu Uchendu, Ted Xiao, Yao Lu, Banghua Zhu, Mengyuan Yan, Joséphine Simon, Matthew Bennice, Chuyuan Fu, Cong Ma, Jiantao Jiao, Sergey Levine, Karol Hausman

In addition, we provide an upper bound on the sample complexity of JSRL and show that with the help of a guide-policy, one can improve the sample complexity for non-optimism exploration methods from exponential in horizon to polynomial.

reinforcement-learning Reinforcement Learning (RL)

BBA-net: A bi-branch attention network for crowd counting

no code implementations22 Jan 2022 Yi Hou, Chengyang Li, Fan Yang, Cong Ma, Liping Zhu, Yuan Li, Huizhu Jia, Xiaodong Xie

Our method can integrate the pedestrian's head and body information to enhance the feature expression ability of the density map.

Crowd Counting

TANet++: Triple Attention Network with Filtered Pointcloud on 3D Detection

no code implementations26 Jun 2021 Cong Ma

TANet is one of state-of-the-art 3D object detection method on KITTI and JRDB benchmark, the network contains a Triple Attention module and Coarse-to-Fine Regression module to improve the robustness and accuracy of 3D Detection.

3D Object Detection Object +1

Scaling and Scalability: Provable Nonconvex Low-Rank Tensor Estimation from Incomplete Measurements

1 code implementation29 Apr 2021 Tian Tong, Cong Ma, Ashley Prater-Bennette, Erin Tripp, Yuejie Chi

Tensors, which provide a powerful and flexible model for representing multi-attribute data and multi-way interactions, play an indispensable role in modern data science across various fields in science and engineering.

Attribute

Bridging Offline Reinforcement Learning and Imitation Learning: A Tale of Pessimism

no code implementations NeurIPS 2021 Paria Rashidinejad, Banghua Zhu, Cong Ma, Jiantao Jiao, Stuart Russell

Based on the composition of the offline dataset, two main categories of methods are used: imitation learning which is suitable for expert datasets and vanilla offline RL which often requires uniform coverage datasets.

Imitation Learning Multi-Armed Bandits +3

Minimax Off-Policy Evaluation for Multi-Armed Bandits

no code implementations19 Jan 2021 Cong Ma, Banghua Zhu, Jiantao Jiao, Martin J. Wainwright

Second, when the behavior policy is unknown, we analyze performance in terms of the competitive ratio, thereby revealing a fundamental gap between the settings of known and unknown behavior policies.

Multi-Armed Bandits Off-policy evaluation

Beyond Procrustes: Balancing-Free Gradient Descent for Asymmetric Low-Rank Matrix Sensing

no code implementations13 Jan 2021 Cong Ma, Yuanxin Li, Yuejie Chi

Low-rank matrix estimation plays a central role in various applications across science and engineering.

Spectral Methods for Data Science: A Statistical Perspective

no code implementations15 Dec 2020 Yuxin Chen, Yuejie Chi, Jianqing Fan, Cong Ma

While the studies of spectral methods can be traced back to classical matrix perturbation theory and methods of moments, the past decade has witnessed tremendous theoretical advances in demystifying their efficacy through the lens of statistical modeling, with the aid of non-asymptotic random matrix theory.

Low-Rank Matrix Recovery with Scaled Subgradient Methods: Fast and Robust Convergence Without the Condition Number

2 code implementations26 Oct 2020 Tian Tong, Cong Ma, Yuejie Chi

Many problems in data science can be treated as estimating a low-rank matrix from highly incomplete, sometimes even corrupted, observations.

Learning Mixtures of Low-Rank Models

no code implementations23 Sep 2020 Yanxi Chen, Cong Ma, H. Vincent Poor, Yuxin Chen

We study the problem of learning mixtures of low-rank models, i. e. reconstructing multiple low-rank matrices from unlabelled linear measurements of each.

Accelerating Ill-Conditioned Low-Rank Matrix Estimation via Scaled Gradient Descent

2 code implementations18 May 2020 Tian Tong, Cong Ma, Yuejie Chi

Low-rank matrix estimation is a canonical problem that finds numerous applications in signal processing, machine learning and imaging science.

Matrix Completion

Microwave Photonic Imaging Radar with a Millimeter-level Resolution

no code implementations9 Apr 2020 Cong Ma, Yue Yang, Ce Liu, Beichen Fan, Xingwei Ye, Yamei Zhang, Xiangchuan Wang, Shilong Pan

Microwave photonic radars enable fast or even real-time high-resolution imaging thanks to its broad bandwidth.

Bridging Convex and Nonconvex Optimization in Robust PCA: Noise, Outliers, and Missing Data

no code implementations15 Jan 2020 Yuxin Chen, Jianqing Fan, Cong Ma, Yuling Yan

This paper delivers improved theoretical guarantees for the convex programming approach in low-rank matrix estimation, in the presence of (1) random noise, (2) gross sparse outliers, and (3) missing data.

Multi-wavelength properties of radio and machine-learning identified counterparts to submillimeter sources in S2COSMOS

no code implementations8 Oct 2019 FangXia An, J. M. Simpson, Ian Smail, A. M. Swinbank, Cong Ma, Daizhong Liu, P. Lang, E. Schinnerer, A. Karim, B. Magnelli, S. Leslie, F. Bertoldi, Chian-Chou Chen, J. E. Geach, Y. Matsuda, S. M. Stach, J. L. Wardlow, B. Gullberg, R. J. Ivison, Y. Ao, R. T. Coogan, A. P. Thomson, S. C. Chapman, R. Wang, Wei-Hao Wang, Y. Yang, R. Asquith, N. Bourne, K. Coppin, N. K. Hine, L. C. Ho, H. S. Hwang, Y. Kato, K. Lacaille, A. J. R. Lewis, I. Oteo, J. Scholtz, M. Sawicki, D. Smith

We identify multi-wavelength counterparts to 1, 147 submillimeter sources from the S2COSMOS SCUBA-2 survey of the COSMOS field by employing a recently developed radio$+$machine-learning method trained on a large sample of ALMA-identified submillimeter galaxies (SMGs), including 260 SMGs identified in the AS2COSMOS pilot survey.

Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics

Inference and Uncertainty Quantification for Noisy Matrix Completion

no code implementations10 Jun 2019 Yuxin Chen, Jianqing Fan, Cong Ma, Yuling Yan

As a byproduct, we obtain a sharp characterization of the estimation accuracy of our de-biased estimators, which, to the best of our knowledge, are the first tractable algorithms that provably achieve full statistical efficiency (including the preconstant).

Matrix Completion Uncertainty Quantification +1

A Selective Overview of Deep Learning

no code implementations10 Apr 2019 Jianqing Fan, Cong Ma, Yiqiao Zhong

Deep learning has arguably achieved tremendous success in recent years.

Noisy Matrix Completion: Understanding Statistical Guarantees for Convex Relaxation via Nonconvex Optimization

no code implementations20 Feb 2019 Yuxin Chen, Yuejie Chi, Jianqing Fan, Cong Ma, Yuling Yan

This paper studies noisy low-rank matrix completion: given partial and noisy entries of a large low-rank matrix, the goal is to estimate the underlying matrix faithfully and efficiently.

Low-Rank Matrix Completion

Implicit Regularization in Nonconvex Statistical Estimation: Gradient Descent Converges Linearly for Phase Retrieval and Matrix Completion

no code implementations ICML 2018 Cong Ma, Kaizheng Wang, Yuejie Chi, Yuxin Chen

Focusing on two statistical estimation problems, i. e. solving random quadratic systems of equations and low-rank matrix completion, we establish that gradient descent achieves near-optimal statistical and computational guarantees without explicit regularization.

Low-Rank Matrix Completion Retrieval

Trajectory Factory: Tracklet Cleaving and Re-connection by Deep Siamese Bi-GRU for Multiple Object Tracking

no code implementations12 Apr 2018 Cong Ma, Changshui Yang, Fan Yang, Yueqing Zhuang, Ziwei Zhang, Huizhu Jia, Xiaodong Xie

In this paper, we propose a novel tracklet processing method to cleave and re-connect tracklets on crowd or long-term occlusion by Siamese Bi-Gated Recurrent Unit (GRU).

Autonomous Driving Multi-Object Tracking +2

Gradient Descent with Random Initialization: Fast Global Convergence for Nonconvex Phase Retrieval

no code implementations21 Mar 2018 Yuxin Chen, Yuejie Chi, Jianqing Fan, Cong Ma

This paper considers the problem of solving systems of quadratic equations, namely, recovering an object of interest $\mathbf{x}^{\natural}\in\mathbb{R}^{n}$ from $m$ quadratic equations/samples $y_{i}=(\mathbf{a}_{i}^{\top}\mathbf{x}^{\natural})^{2}$, $1\leq i\leq m$.

Retrieval

Nonconvex Matrix Factorization from Rank-One Measurements

no code implementations17 Feb 2018 Yuanxin Li, Cong Ma, Yuxin Chen, Yuejie Chi

We consider the problem of recovering low-rank matrices from random rank-one measurements, which spans numerous applications including covariance sketching, phase retrieval, quantum state tomography, and learning shallow polynomial neural networks, among others.

Quantum State Tomography Retrieval

Inter-Subject Analysis: Inferring Sparse Interactions with Dense Intra-Graphs

no code implementations20 Sep 2017 Cong Ma, Junwei Lu, Han Liu

Our framework is based on the Gaussian graphical models, under which ISA can be converted to the problem of estimation and inference of the inter-subject precision matrix.

valid

Multi-modal Summarization for Asynchronous Collection of Text, Image, Audio and Video

no code implementations EMNLP 2017 Haoran Li, Junnan Zhu, Cong Ma, Jiajun Zhang, Cheng-qing Zong

In this work, we propose an extractive Multi-modal Summarization (MMS) method which can automatically generate a textual summary given a set of documents, images, audios and videos related to a specific topic.

Automatic Speech Recognition (ASR) Document Summarization +1

Spectral Method and Regularized MLE Are Both Optimal for Top-$K$ Ranking

no code implementations31 Jul 2017 Yuxin Chen, Jianqing Fan, Cong Ma, Kaizheng Wang

This paper is concerned with the problem of top-$K$ ranking from pairwise comparisons.

Application of Bayesian graphs to SN Ia data analysis and compression

3 code implementations28 Mar 2016 Cong Ma, Pier-Stefano Corasaniti, Bruce A. Bassett

Overall, the results of our analysis emphasize the need for a fully consistent Bayesian statistical approach in the analysis of future large SN Ia data sets.

Cosmology and Nongalactic Astrophysics

Panther: Fast Top-k Similarity Search in Large Networks

2 code implementations10 Apr 2015 Jing Zhang, Jie Tang, Cong Ma, Hanghang Tong, Yu Jing, Juanzi Li

The algorithm is based on a novel idea of random path, and an extended method is also presented, to enhance the structural similarity when two vertices are completely disconnected.

Social and Information Networks

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