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Optimal prediction of Markov chains with and without spectral gap

Neural Information Processing Systems

We study the following learning problem with dependent data: Given a trajectory of length $n$ from a stationary Markov chain with $k$ states, the goal is to predict the distribution of the next state.


Metacognitive Capabilities of LLMs: An Exploration in Mathematical Problem Solving

Neural Information Processing Systems

Today's best LLMs clearly possess some reasoning processes. The paper gives evidence that they also have metacognitive knowledge, including ability to name skills and procedures to apply given a task. We explore this primarily in context of math reasoning, developing a prompt-guided interaction procedure to get a powerful LLM to assign sensible skill labels to math questions, followed by having it perform semantic clustering to obtain coarser families of skill labels. These coarse skill labels look interpretable to humans.To validate that these skill labels are meaningful and relevant to the LLM's reasoning processes we perform the following experiments.


Achieving Near-Optimal Convergence for Distributed Minimax Optimization with Adaptive Stepsizes

Neural Information Processing Systems

In this paper, we show that applying adaptive methods directly to distributed minimax problems can result in non-convergence due to inconsistency in locally computed adaptive stepsizes. To address this challenge, we propose D-AdaST, a Distributed Adaptive minimax method with Stepsize Tracking. The key strategy is to employ an adaptive stepsize tracking protocol involving the transmission of two extra (scalar) variables. This protocol ensures the consistency among stepsizes of nodes, eliminating the steady-state error due to the lack of coordination of stepsizes among nodes that commonly exists in vanilla distributed adaptive methods, and thus guarantees exact convergence. For nonconvex-strongly-concave distributed minimax problems, we characterize the specific transient times that ensure time-scale separation of stepsizes and quasi-independence of networks, leading to a near-optimal convergence rate of $\tilde{\mathcal{O}} \left( \epsilon ^{-\left( 4+\delta \right)} \right)$ for any small $\delta > 0$, matching that of the centralized counterpart. To our best knowledge, D-AdaST is the *first* distributed adaptive method achieving near-optimal convergence without knowing any problem-dependent parameters for nonconvex minimax problems. Extensive experiments are conducted to validate our theoretical results.


Ryan Gosling on bringing humour to sci-fi adventure Project Hail Mary

BBC News

Humour and science fiction may not seem obvious bedfellows but a history of cinema will tell you different. Think Spaceballs, Mars Attacks! and Everything Everwhere All At Once to name but a few. And now Ryan Gosling is hopping on board. The 45-year-old is both the lead actor and producer of Project Hail Mary, a space adventure film based on the 2021 Andy Weir novel of the same name. While Gosling has showcased his comedy chops in films such as Barbie and Nice Guys, he tells the BBC he's always struggled as an actor because I would want to bring humour to something but has found opportunities to be funny limited with some projects.


LookHere: Vision Transformers with Directed Attention Generalize and Extrapolate

Neural Information Processing Systems

High-resolution images offer more information about scenes that can improve model accuracy. However, the dominant model architecture in computer vision, the vision transformer (ViT), cannot effectively leverage larger images without finetuning -- ViTs poorly extrapolate to more patches at test time, although transformers offer sequence length flexibility. We attribute this shortcoming to the current patch position encoding methods, which create a distribution shift when extrapolating.We propose a drop-in replacement for the position encoding of plain ViTs that restricts attention heads to fixed fields of view, pointed in different directions, using 2D attention masks. Our novel method, called LookHere, provides translation-equivariance, ensures attention head diversity, and limits the distribution shift that attention heads face when extrapolating. We demonstrate that LookHere improves performance on classification (avg.


DEFT: Efficient Fine-tuning of Diffusion Models by Learning the Generalised h -transform

Neural Information Processing Systems

Generative modelling paradigms based on denoising diffusion processes have emerged as a leading candidate for conditional sampling in inverse problems. In many real-world applications, we often have access to large, expensively trained unconditional diffusion models, which we aim to exploit for improving conditional sampling.Most recent approaches are motivated heuristically and lack a unifying framework, obscuring connections between them. Further, they often suffer from issues such as being very sensitive to hyperparameters, being expensive to train or needing access to weights hidden behind a closed API. In this work, we unify conditional training and sampling using the mathematically well-understood Doob's h-transform. This new perspective allows us to unify many existing methods under a common umbrella. Under this framework, we propose DEFT (Doob's h-transform Efficient FineTuning), a new approach for conditional generation that simply fine-tunes a very small network to quickly learn the conditional $h$-transform, while keeping the larger unconditional network unchanged. DEFT is much faster than existing baselines while achieving state-of-the-art performance across a variety of linear and non-linear benchmarks. On image reconstruction tasks, we achieve speedups of up to 1.6$\times$, while having the best perceptual quality on natural images and reconstruction performance on medical images. Further, we also provide initial experiments on protein motif scaffolding and outperform reconstruction guidance methods.


Progressive Entropic Optimal Transport Solvers

Neural Information Processing Systems

Optimal transport (OT) has profoundly impacted machine learning by providing theoretical and computational tools to realign datasets.In this context, given two large point clouds of sizes $n$ and $m$ in $\mathbb{R}^d$, entropic OT (EOT) solvers have emerged as the most reliable tool to either solve the Kantorovich problem and output a $n\times m$ coupling matrix, or to solve the Monge problem and learn a vector-valued push-forward map. While the robustness of EOT couplings/maps makes them a go-to choice in practical applications, EOT solvers remain difficult to tune because of a small but influential set of hyperparameters, notably the omnipresent entropic regularization strength $\varepsilon$. Setting $\varepsilon$ can be difficult, as it simultaneously impacts various performance metrics, such as compute speed, statistical performance, generalization, and bias. In this work, we propose a new class of EOT solvers (ProgOT), that can estimate both plans and transport maps.We take advantage of several opportunities to optimize the computation of EOT solutions by *dividing* mass displacement using a time discretization, borrowing inspiration from dynamic OT formulations, and *conquering* each of these steps using EOT with properly scheduled parameters. We provide experimental evidence demonstrating that ProgOT is a faster and more robust alternative to *standard solvers* when computing couplings at large scales, even outperforming neural network-based approaches. We also prove statistical consistency of our approach for estimating OT maps.


Revisiting Few-Shot Object Detection with Vision-Language Models

Neural Information Processing Systems

The era of vision-language models (VLMs) trained on web-scale datasets challenges conventional formulations of "open-world perception. In this work, we revisit the task of few-shot object detection (FSOD) in the context of recent foundational VLMs. First, we point out that zero-shot predictions from VLMs such as GroundingDINO significantly outperform state-of-the-art few-shot detectors (48 vs. 33 AP) on COCO. Despite their strong zero-shot performance, such foundation models may still be sub-optimal. For example, trucks on the web may be defined differently from trucks for a target applications such as autonomous vehicle perception.


Beyond Slow Signs in High-fidelity Model Extraction

Neural Information Processing Systems

Deep neural networks, costly to train and rich in intellectual property value, areincreasingly threatened by model extraction attacks that compromise their confiden-tiality. Previous attacks have succeeded in reverse-engineering model parametersup to a precision of float64 for models trained on random data with at most threehidden layers using cryptanalytical techniques. However, the process was identifiedto be very time consuming and not feasible for larger and deeper models trained onstandard benchmarks. Our study evaluates the feasibility of parameter extractionmethods of Carlini et al. [1] further enhanced by Canales-Martínez et al. [2] formodels trained on standard benchmarks. We introduce a unified codebase thatintegrates previous methods and reveal that computational tools can significantlyinfluence performance. We develop further optimisations to the end-to-end attackand improve the efficiency of extracting weight signs by up to 14.8 times com-pared to former methods through the identification of easier and harder to extractneurons. Contrary to prior assumptions, we identify extraction of weights, notextraction of weight signs, as the critical bottleneck. With our improvements, a16,721 parameter model with 2 hidden layers trained on MNIST is extracted withinonly 98 minutes compared to at least 150 minutes previously. Finally, addressingmethodological deficiencies observed in previous studies, we propose new ways ofrobust benchmarking for future model extraction attacks.


ShareGPT4Video: Improving Video Understanding and Generation with Better Captions

Neural Information Processing Systems

We present the ShareGPT4Video series, aiming to facilitate the video understanding of large video-language models (LVLMs) and the video generation of text-to-video models (T2VMs) via dense and precise captions. The series comprises: 1) ShareGPT4Video, 40K GPT4V annotated dense captions of videos with various lengths and sources, developed through carefully designed data filtering and annotating strategy.