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Omar Khattab

17 accepted papers

2026

GEPA: Reflective Prompt Evolution Can Outperform Reinforcement Learning

ICLR 2026oral

Large language models (LLMs) are increasingly adapted to downstream tasks via reinforcement learning (RL) methods like Group Relative Policy Optimization (GRPO), which often require thousands of rollouts to learn new tasks. We argue that the interpretable nature of language often provides a much ric…

Cited by 0SourcecodeScholar
2025

FreshStack: Building Realistic Benchmarks for Evaluating Retrieval on Technical Documents

NeurIPS 2025poster

We introduce FreshStack, a holistic framework for automatically building information retrieval (IR) evaluation benchmarks by incorporating challenging questions and answers. FreshStack conducts the following steps: (1) automatic corpus collection from code and technical documentation, (2) nugget gen…

Cited by 0SourceScholar
2025

Grounding by Trying: LLMs with Reinforcement Learning-Enhanced Retrieval

ICLR 2025poster

The hallucinations of large language models (LLMs) are increasingly mitigated by allowing LLMs to search for information and to ground their answers in real sources. Unfortunately, LLMs often struggle with posing the right search queries, especially when dealing with complex or otherwise indirect to…

Cited by 5SourcePDFScholar
2025

LangProBe: a Language Program Benchmark

EMNLP 2025

Composing language models (LMs) into multi-step language programs and automatically optimizing their modular prompts is now a mainstream paradigm for building AI systems, but the tradeoffs in this space have only scarcely been studied before. We introduce LangProBe, the first large-scale benchmark f

Cited by 0SourcePDFScholar
2025

PAPILLON: Privacy Preservation from Internet-based and Local Language Model Ensembles

NAACL 2025long

Users can divulge sensitive information to proprietary LLM providers, raising significant privacy concerns. While open-source models, hosted locally on the user’s machine, alleviate some concerns, models that users can host locally are often less capable than proprietary frontier models. Toward pres…

Cited by 5SourcePDFScholar
2024

ARES: An Automated Evaluation Framework for Retrieval-Augmented Generation Systems

NAACL 2024long

Evaluating retrieval-augmented generation (RAG) systems traditionally relies on hand annotations for input queries, passages to retrieve, and responses to generate. We introduce ARES, an Automated RAG Evaluation System, for evaluating RAG systems along the dimensions of context relevance, answer fai…

2024

Assisting in Writing Wikipedia-like Articles From Scratch with Large Language Models

NAACL 2024long

We study how to apply large language models to write grounded and organized long-form articles from scratch, with comparable breadth and depth to Wikipedia pages. This underexplored problem poses new challenges at the pre-writing stage, including how to research the topic and prepare an outline prio…

2024

DSPy: Compiling Declarative Language Model Calls into State-of-the-Art Pipelines

ICLR 2024spotlight

The ML community is rapidly exploring techniques for prompting language models (LMs) and for stacking them into pipelines that solve complex tasks. Unfortunately, existing LM pipelines are typically implemented using hard-coded “prompt templates”, i.e. lengthy strings discovered via trial and error.…

2024

Fine-Tuning and Prompt Optimization: Two Great Steps that Work Better Together

EMNLP 2024main

Natural Language Processing (NLP) systems are increasingly taking the form of sophisticated modular pipelines, e.g., Retrieval Augmented Generation (RAG), where each module may involve a distinct Language Model (LM) and an associated prompt template. These compound systems often lack intermediate la…

Cited by 14SourcePDFScholar
2024

IndicIRSuite: Multilingual Dataset and Neural Information Models for Indian Languages

ACL 2024short

In this paper, we introduce Neural Information Retrieval resources for 11 widely spoken Indian Languages (Assamese, Bengali, Gujarati, Hindi, Kannada, Malayalam, Marathi, Oriya, Punjabi, Tamil, and Telugu) from two major Indian language families (Indo-Aryan and Dravidian). These resources include (a…

2024

Optimizing Instructions and Demonstrations for Multi-Stage Language Model Programs

EMNLP 2024main

Language Model Programs, i.e. sophisticated pipelines of modular language model (LM) calls, are increasingly advancing NLP tasks, but they require crafting prompts that are jointly effective for all modules. We study prompt optimization for LM programs, i.e. how to update these prompts to maximize a…

2024

Problem-Oriented Segmentation and Retrieval: Case Study on Tutoring Conversations

EMNLP 2024finding

Many open-ended conversations (e.g., tutoring lessons or business meetings) revolve around pre-defined reference materials, like worksheets or meeting bullets. To provide a framework for studying such conversation structure, we introduce *Problem-Oriented Segmentation & Retrieval (POSR), the task of…

2023

Moving Beyond Downstream Task Accuracy for Information Retrieval Benchmarking

ACL 2023findings

Neural information retrieval (IR) systems have progressed rapidly in recent years, in large part due to the release of publicly available benchmarking tasks. Unfortunately, some dimensions of this progress are illusory: the majority of the popular IR benchmarks today focus exclusively on downstream…

2023

UDAPDR: Unsupervised Domain Adaptation via LLM Prompting and Distillation of Rerankers

EMNLP 2023long main

Many information retrieval tasks require large labeled datasets for fine-tuning. However, such datasets are often unavailable, and their utility for real-world applications can diminish quickly due to domain shifts. To address this challenge, we develop and motivate a method for using large language…

Cited by 0SourcecodeScholar
2022

ColBERTv2: Effective and Efficient Retrieval via Lightweight Late Interaction

NAACL 2022long

Neural information retrieval (IR) has greatly advanced search and other knowledge-intensive language tasks. While many neural IR methods encode queries and documents into single-vector representations, late interaction models produce multi-vector representations at the granularity of each token and…

2022

Hindsight: Posterior-guided training of retrievers for improved open-ended generation

ICLR 2022poster

Many text generation systems benefit from retrieving passages from a textual knowledge corpus (e.g., Wikipedia) and using them to generate the output. For open-ended generation tasks, like generating informative utterances in conversations, many varied passages $z$ are relevant to the context $x$ bu…

Cited by 49SourcePDFScholar
2021

Baleen: Robust Multi-Hop Reasoning at Scale via Condensed Retrieval

NeurIPS 2021spotlight

Multi-hop reasoning (i.e., reasoning across two or more documents) is a key ingredient for NLP models that leverage large corpora to exhibit broad knowledge. To retrieve evidence passages, multi-hop models must contend with a fast-growing search space across the hops, represent complex queries that…

Cited by 65SourcePDFScholar