While dense retrieval has been shown effective and efficient across tasks and languages, it remains difficult to create effective fully zero-shot dense retrieval systems when no relevance label is available. In this paper, we recognize the difficulty of zero-shot learning and encoding relevance. Instead, we propose to pivot through Hypothetical Document Embeddings~(HyDE). Given a query, HyDE first zero-shot instructs an instruction-following language model (e.g. InstructGPT) to generate a hypothetical document. The document captures relevance patterns but is unreal and may contain false details. Then, an unsupervised contrastively learned encoder~(e.g. Contriever) encodes the document into an embedding vector. This vector identifies a neighborhood in the corpus embedding space, where similar real documents are retrieved based on vector similarity. This second step ground the generated document to the actual corpus, with the encoder's dense bottleneck filtering out the incorrect details. Our experiments show that HyDE significantly outperforms the state-of-the-art unsupervised dense retriever Contriever and shows strong performance comparable to fine-tuned retrievers, across various tasks (e.g. web search, QA, fact verification) and languages~(e.g. sw, ko, ja).

Deep neural networks (DNNs) are often used for text classification tasks as they usually achieve high levels of accuracy. However, DNNs can be computationally intensive with billions of parameters and large amounts of labeled data, which can make them expensive to use, to optimize and to transfer to out-of-distribution (OOD) cases in practice. In this paper, we propose a non-parametric alternative to DNNs that's easy, light-weight and universal in text classification: a combination of a simple compressor like gzip with a $k$-nearest-neighbor classifier. Without any training, pre-training or fine-tuning, our method achieves results that are competitive with non-pretrained deep learning methods on six in-distributed datasets. It even outperforms BERT on all five OOD datasets, including four low-resource languages. Our method also performs particularly well in few-shot settings where labeled data are too scarce for DNNs to achieve a satisfying accuracy.

The application of natural language processing (NLP) to cancer pathology reports has been focused on detecting cancer cases, largely ignoring precancerous cases. Improving the characterization of precancerous adenomas assists in developing diagnostic tests for early cancer detection and prevention, especially for colorectal cancer (CRC). Here we developed transformer-based deep neural network NLP models to perform the CRC phenotyping, with the goal of extracting precancerous lesion attributes and distinguishing cancer and precancerous cases. We achieved 0.914 macro-F1 scores for classifying patients into negative, non-advanced adenoma, advanced adenoma and CRC. We further improved the performance to 0.923 using an ensemble of classifiers for cancer status classification and lesion size named entity recognition (NER). Our results demonstrated the potential of using NLP to leverage real-world health record data to facilitate the development of diagnostic tests for early cancer prevention.

Large-scale diffusion neural networks represent a substantial milestone in text-to-image generation, but they remain poorly understood, lacking interpretability analyses. In this paper, we perform a text-image attribution analysis on Stable Diffusion, a recently open-sourced model. To produce pixel-level attribution maps, we upscale and aggregate cross-attention word-pixel scores in the denoising subnetwork, naming our method DAAM. We evaluate its correctness by testing its semantic segmentation ability on nouns, as well as its generalized attribution quality on all parts of speech, rated by humans. We then apply DAAM to study the role of syntax in the pixel space, characterizing head--dependent heat map interaction patterns for ten common dependency relations. Finally, we study several semantic phenomena using DAAM, with a focus on feature entanglement, where we find that cohyponyms worsen generation quality and descriptive adjectives attend too broadly. To our knowledge, we are the first to interpret large diffusion models from a visuolinguistic perspective, which enables future lines of research. Our code is at https://github.com/castorini/daam.

存在多种自然语言处理（NLP）任务的多种效率方法，例如修剪，蒸馏，动态推断，量化等。我们可以将效率方法视为应用于模型的操作员。自然，我们可以构建多个效率方法的管道，即，顺序将多个操作员应用于模型。在本文中，我们研究了这一想法的合理性，更重要的是，效率运营商的合理性和累积性。我们做出了两个有趣的观察结果：（1）效率运营商是可交换的 - 管道中效率方法的顺序对最终结果几乎没有影响；（2）效率运算符也是累积的 - 结合几种效率方法的最终结果可以通过组合单个方法的结果来估算。这些观察结果加深了我们对效率运营商的理解，并为其现实世界应用提供了有用的准则。

预计机器学习算法的大多数实际问题都可以通过1）未知数据分配来解决这种情况； 2）小领域特定知识； 3）注释有限的数据集。我们通过使用潜在变量（NPC-LV）的压缩提出非参数学习，这是任何数据集的学习框架，这些数据集具有丰富的未标记数据，但很少有标签的数据。通过仅以无监督的方式训练生成模型，该框架利用数据分配来构建压缩机。使用源自Kolmogorov复杂性的基于压缩机的距离度量，加上很少的标记数据，NPC-LV无需进一步的训练而进行分类。我们表明，在低数据制度中，NPC-LV在图像分类的所有三个数据集上都优于监督方法，甚至超过了CIFAR-10上的半监督学习方法。我们证明了如何以及何时使用负面证据下降（Nelbo）作为分类的近似压缩长度。通过揭示压缩率和分类精度之间的相关性，我们说明在NPC-LV下，生成模型的改进可以增强下游分类精度。

稀疏的词汇表现学习已经证明了在近期模型中提高通道检索效果，例如Deepumact，Unicoil和Splade。本文介绍了一种简单而有效的方法，用于通过引入稀疏屏蔽方案来控制稀疏性和自学方法来控制诽谤和自学方法来模拟脱锁表示模拟缺陷表示来缩小通道检索的词汇表格的简单但有效的方法。我们模型的基本实施具有更精致的方法，实现了有效性和效率之间的良好平衡。我们的方法简单地为未来的词汇表达学习探索开辟了门，以便检索。

本文概述了了解信息检索和自然语言处理中最近的发展的概念框架，试图集成密集和稀疏检索方法。我提出了一种代表性方法，将核心文本检索问题与逻辑评分模型和物理检索模型中断。评分模型在编码器方面定义，将查询和文档映射到代表空间，以及计算查询文档分数的比较函数。物理检索模型定义了系统如何从关于查询的任意大语料库产生顶级k $ Scoring文档。分别沿两个维度进一步分析得分模型：密集与稀疏表示和监督（学习）与无监督的方法。我展示了许多最近提出的检索方法，包括多级排名设计，可以看作是本框架中的不同参数化，并且统一视图表明了许多开放的研究问题，为未来的工作提供了路线图。作为奖金，这种概念框架在计算时建立了与自然语言处理和信息访问“技术”中的句子相似任务的连接。

我们在11个类型的类型不同语言中展示了一个用于单语言检索的多语言基准数据集的Tydi先生，旨在评估与学习的密集表示的排名。该资源的目标是以非英语语言的密集检索技术进行培训，最近的观察结果是当应用于分发超出数据时的表示学习的现有技术表现不佳。作为一个起点，我们基于我们称之为“MDPR”的多语言调整，为此新数据集提供零拍摄线。实验表明，尽管MDPR的有效性远低于BM25，但仍然似乎提供了有价值的相关信号，改善了BM25导致稀疏致密的杂种。除了对我们的结果分析外，我们还讨论了未来的挑战，并在多语言密集检索中展示了一个研究议程。Tydi先生可以在https://github.com/castorini/mr.tydi下载。

Non-linear state-space models, also known as general hidden Markov models, are ubiquitous in statistical machine learning, being the most classical generative models for serial data and sequences in general. The particle-based, rapid incremental smoother PaRIS is a sequential Monte Carlo (SMC) technique allowing for efficient online approximation of expectations of additive functionals under the smoothing distribution in these models. Such expectations appear naturally in several learning contexts, such as likelihood estimation (MLE) and Markov score climbing (MSC). PARIS has linear computational complexity, limited memory requirements and comes with non-asymptotic bounds, convergence results and stability guarantees. Still, being based on self-normalised importance sampling, the PaRIS estimator is biased. Our first contribution is to design a novel additive smoothing algorithm, the Parisian particle Gibbs PPG sampler, which can be viewed as a PaRIS algorithm driven by conditional SMC moves, resulting in bias-reduced estimates of the targeted quantities. We substantiate the PPG algorithm with theoretical results, including new bounds on bias and variance as well as deviation inequalities. Our second contribution is to apply PPG in a learning framework, covering MLE and MSC as special examples. In this context, we establish, under standard assumptions, non-asymptotic bounds highlighting the value of bias reduction and the implicit Rao--Blackwellization of PPG. These are the first non-asymptotic results of this kind in this setting. We illustrate our theoretical results with numerical experiments supporting our claims.