Blockchains offer strong security gurarantees, but cannot protect users against the ordering of transactions. Players such as miners, bots and validators can reorder various transactions and reap significant profits, called the Maximal Extractable Value (MEV). In this paper, we propose an MEV aware protocol design called Masquerade, and show that it will increase user satisfaction and confidence in the system. We propose a strict per-transaction level of ordering to ensure that a transaction is committed either way even if it is revealed. In this protocol, we introduce the notion of a "token" to mitigate the actions taken by an adversary in an attack scenario. Such tokens can be purchased voluntarily by users, who can then choose to include the token numbers in their transactions. If the users include the token in their transactions, then our protocol requires the block-builder to order the transactions strictly according to token numbers. We show through extensive simulations that this reduces the probability that the adversaries can benefit from MEV transactions as compared to existing current practices.
Alignment is of critical importance for training large language models (LLMs). The predominant strategy to address this is through Reinforcement Learning from Human Feedback (RLHF), where PPO serves as the de-facto algorithm. Yet, PPO is known to suffer from computational inefficiency, which is a challenge that this paper aims to address. We identify three important properties in RLHF tasks: fast simulation, deterministic transitions, and trajectory-level rewards, which are not leveraged in PPO. Based on such observations, we develop a new algorithm tailored for RLHF, called ReMax. The algorithm design of ReMax is built on a celebrated algorithm REINFORCE but is equipped with a new variance-reduction technique. Our method has three-fold advantages over PPO: first, ReMax is simple to implement and removes many hyper-parameters in PPO, which are scale-sensitive and laborious to tune. Second, ReMax saves about 50% memory usage in principle. As a result, PPO runs out-of-memory when fine-tuning a Llama2 (7B) model on 8xA100-40GB GPUs, whereas ReMax can afford training. This memory improvement is achieved by removing the value model in PPO. Third, based on our calculations, we find that even assuming PPO can afford the training of Llama2 (7B), it would still run about 2x slower than ReMax. This is due to the computational overhead of the value model, which does not exist in ReMax. Importantly, the above computational improvements do not sacrifice the performance. We hypothesize these advantages can be maintained in larger-scaled models. Our implementation of ReMax is available at //github.com/liziniu/ReMax
Alignment is of critical importance for training large language models (LLMs). The predominant strategy to address this is through Reinforcement Learning from Human Feedback (RLHF), where PPO serves as the de-facto algorithm. Yet, PPO is known to suffer from computational inefficiency, a challenge that this paper aims to address. We identify three important properties in RLHF tasks: fast simulation, deterministic transitions, and trajectory-level rewards, which are not leveraged in PPO. Based on such observations, we develop a new algorithm tailored for RLHF, called ReMax. The algorithm design of ReMax is built on a celebrated algorithm REINFORCE but is equipped with a new variance-reduction technique. Our method has three-fold advantages over PPO: first, it saves about 50% memory usage in principle. As a result, PPO runs out-of-memory when fine-tuning a Llama2 (7B) model on 8xA100-40GB GPUs, whereas ReMax can afford training. This memory improvement is achieved by removing the value model in PPO. Second, ReMax is simple to implement and removes many hyper-parameters in PPO, which are scale-sensitive and laborious to tune. Third, on GPT2 (137M), we observe 2.2x speed-up in terms of wall-clock time. Importantly, the above computational improvements do not sacrifice the performance. We hypothesize these advantages can be maintained in larger-scaled models. Our implementation of ReMax is available at //github.com/liziniu/ReMax
Language agents have shown some ability to interact with an external environment, e.g., a virtual world such as ScienceWorld, to perform complex tasks, e.g., growing a plant, without the startup costs of reinforcement learning. However, despite their zero-shot capabilities, these agents to date do not continually improve over time beyond performance refinement on a specific task. Here we present CLIN, the first language-based agent to achieve this, so that it continually improves over multiple trials, including when both the environment and task are varied, and without requiring parameter updates. Our approach is to use a persistent, dynamic, textual memory centered on causal abstractions (rather than general "helpful hints") that is regularly updated after each trial so that the agent gradually learns useful knowledge for new trials. In the ScienceWorld benchmark, CLIN is able to continually improve on repeated trials on the same task and environment, outperforming state-of-the-art reflective language agents like Reflexion by 23 absolute points. CLIN can also transfer its learning to new environments (or new tasks), improving its zero-shot performance by 4 points (13 for new tasks) and can further improve performance there through continual memory updates, enhancing performance by an additional 17 points (7 for new tasks). This suggests a new architecture for agents built on frozen models that can still continually and rapidly improve over time.
Personalized news recommendation aims to assist users in finding news articles that align with their interests, which plays a pivotal role in mitigating users' information overload problem. Although many recent works have been studied for better user and news representations, the following challenges have been rarely studied: (C1) How to precisely comprehend a range of intents coupled within a news article? and (C2) How to differentiate news articles with varying post-read preferences in users' click history? To tackle both challenges together, in this paper, we propose a novel personalized news recommendation framework (CIDER) that employs (1) category-guided intent disentanglement for (C1) and (2) consistency-based news representation for (C2). Furthermore, we incorporate a category prediction into the training process of CIDER as an auxiliary task, which provides supplementary supervisory signals to enhance intent disentanglement. Extensive experiments on two real-world datasets reveal that (1) CIDER provides consistent performance improvements over seven state-of-the-art news recommendation methods and (2) the proposed strategies significantly improve the model accuracy of CIDER.
Traditional recommender systems have heavily relied on identity representations (IDs) to model users and items, while the ascendancy of pre-trained language model (PLM) encoders has enriched the modeling of contextual item descriptions. However, PLMs, although effective in addressing few-shot, zero-shot, or unified modeling scenarios, often neglect the crucial collaborative filtering signal. This neglect gives rise to two pressing challenges: (1) Collaborative Contextualization, the seamless integration of collaborative signals with contextual representations. (2) the imperative to bridge the representation gap between ID-based representations and contextual representations while preserving their contextual semantics. In this paper, we propose CollabContext, a novel model that adeptly combines collaborative filtering signals with contextual representations and aligns these representations within the contextual space, preserving essential contextual semantics. Experimental results across three real-world datasets demonstrate substantial improvements. Leveraging collaborative contextualization, CollabContext can also be effectively applied to cold-start scenarios, achieving remarkable enhancements in recommendation performance. The code is available after the conference accepts the paper.
In order to fully unlock the transformative power of distributed ledgers and blockchains, it is crucial to develop innovative consensus algorithms that can overcome the obstacles of security, scalability, and interoperability, which currently hinder their widespread adoption. This paper introduces HybridChain that combines the advantages of sharded blockchain and DAG distributed ledger, and a consensus algorithm that leverages decentralized learning. Our approach involves validators exchanging perceptions as votes to assess potential conflicts between transactions and the witness set, representing input transactions in the UTXO model. These perceptions collectively contribute to an intermediate belief regarding the validity of transactions. By integrating their beliefs with those of other validators, localized decisions are made to determine validity. Ultimately, a final consensus is achieved through a majority vote, ensuring precise and efficient validation of transactions. Our proposed approach is compared to the existing DAG-based scheme IOTA and the sharded blockchain Omniledger through extensive simulations. The results show that IOTA has high throughput and low latency but sacrifices accuracy and is vulnerable to orphanage attacks especially with low transaction rates. Omniledger achieves stable accuracy by increasing shards but has increased latency. In contrast, the proposed HybridChain exhibits fast, accurate, and secure transaction processing, and excellent scalability.
Programmers increasingly rely on Large Language Models (LLMs) for code generation. However, they now have to deal with issues like having to constantly switch between generating and verifying code, caused by misalignment between programmers' prompts and the generated code. Unfortunately, current LLM-driven code assistants provide insufficient support during the prompt authoring process to help programmers tackle these challenges emerging from the new workflow. To address these challenges, we employed an iterative design process to understand programmers' strategies when programming with LLMs. Based on our findings, we developed CoLadder, a system that assists programmers by enabling hierarchical task decomposition, incremental code generation, and verification of results during prompt authoring. A user study with 12 experienced programmers showed that CoLadder is effective in helping programmers externalize their mental models flexibly, improving their ability to navigate and edit code across various abstraction levels, from initial intent to final code implementation.
This paper aims to tackle the challenge of dynamic view synthesis from multi-view videos. The key observation is that while previous grid-based methods offer consistent rendering, they fall short in capturing appearance details of a complex dynamic scene, a domain where multi-view image-based rendering methods demonstrate the opposite properties. To combine the best of two worlds, we introduce Im4D, a hybrid scene representation that consists of a grid-based geometry representation and a multi-view image-based appearance representation. Specifically, the dynamic geometry is encoded as a 4D density function composed of spatiotemporal feature planes and a small MLP network, which globally models the scene structure and facilitates the rendering consistency. We represent the scene appearance by the original multi-view videos and a network that learns to predict the color of a 3D point from image features, instead of memorizing detailed appearance totally with networks, thereby naturally making the learning of networks easier. Our method is evaluated on five dynamic view synthesis datasets including DyNeRF, ZJU-MoCap, NHR, DNA-Rendering and ENeRF-Outdoor datasets. The results show that Im4D exhibits state-of-the-art performance in rendering quality and can be trained efficiently, while realizing real-time rendering with a speed of 79.8 FPS for 512x512 images, on a single RTX 3090 GPU.
Recent advancements in autonomous driving have relied on data-driven approaches, which are widely adopted but face challenges including dataset bias, overfitting, and uninterpretability. Drawing inspiration from the knowledge-driven nature of human driving, we explore the question of how to instill similar capabilities into autonomous driving systems and summarize a paradigm that integrates an interactive environment, a driver agent, as well as a memory component to address this question. Leveraging large language models with emergent abilities, we propose the DiLu framework, which combines a Reasoning and a Reflection module to enable the system to perform decision-making based on common-sense knowledge and evolve continuously. Extensive experiments prove DiLu's capability to accumulate experience and demonstrate a significant advantage in generalization ability over reinforcement learning-based methods. Moreover, DiLu is able to directly acquire experiences from real-world datasets which highlights its potential to be deployed on practical autonomous driving systems. To the best of our knowledge, we are the first to instill knowledge-driven capability into autonomous driving systems from the perspective of how humans drive.
Recommender systems are important and powerful tools for various personalized services. Traditionally, these systems use data mining and machine learning techniques to make recommendations based on correlations found in the data. However, relying solely on correlation without considering the underlying causal mechanism may lead to various practical issues such as fairness, explainability, robustness, bias, echo chamber and controllability problems. Therefore, researchers in related area have begun incorporating causality into recommendation systems to address these issues. In this survey, we review the existing literature on causal inference in recommender systems. We discuss the fundamental concepts of both recommender systems and causal inference as well as their relationship, and review the existing work on causal methods for different problems in recommender systems. Finally, we discuss open problems and future directions in the field of causal inference for recommendations.