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William Merrill
1,675 posts
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William Merrill
@lambdaviking
incoming Prof @TTIC_Connect theory and pretraining at @allen_ai Will irl, TC0 enthusiast
Seattle, WA
lambdaviking.com
Joined October 2011
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  • Pinned
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    William Merrill
    @lambdaviking
    Oct 7, 2025
    My thesis, 𝘈 𝘵𝘩𝘦𝘰𝘳𝘺 𝘰𝘧 𝘵𝘩𝘦 𝘤𝘰𝘮𝘱𝘶𝘵𝘢𝘵𝘪𝘰𝘯𝘢𝘭 𝘱𝘰𝘸𝘦𝘳 𝘢𝘯𝘥 𝘭𝘪𝘮𝘪𝘵𝘢𝘵𝘪𝘰𝘯𝘴 𝘰𝘧 𝘭𝘢𝘯𝘨𝘶𝘢𝘨𝘦 𝘮𝘰𝘥𝘦𝘭𝘪𝘯𝘨 𝘢𝘳𝘤𝘩𝘪𝘵𝘦𝘤𝘵𝘶𝘳𝘦𝘴, is now online:
    30K
  • user avatar
    William Merrill
    @lambdaviking
    Apr 16, 2024
    ✨Excited to finally drop our new paper: SSMs “look like” RNNs, but we show their statefulness is an illusion🪄🐇 Current SSMs cannot express basic state tracking, but a minimal change fixes this! 👀 w/ @jowenpetty, @Ashish_S_AI arxiv.org/abs/2404.08819
    411K
  • user avatar
    William Merrill
    @lambdaviking
    May 26, 2023
    📣 @Ashish_S_AI and I prove that transformers can be translated to sentences in first-order logic with majority-vote quantifiers (FOM). FOM is a symbolic language that can capture computation inside transformers! arxiv.org/abs/2210.02671
    121K
  • user avatar
    William Merrill
    @lambdaviking
    Mar 7, 2025
    How does the depth of a transformer affect reasoning capabilities? New preprint by myself and @Ashish_S_AI shows that a little depth goes a long way to increase transformers’ expressive power We take this as encouraging for further research on looped transformers!🧵
    A Little Depth Goes a Long Way: The Expressive Power of Log-Depth Transformers
    52K
  • user avatar
    William Merrill
    @lambdaviking
    Apr 30, 2025
    Excited to announce I'll be starting as an assistant professor at @TTIC_Connect for fall 2026! In the meantime, I'll be graduating and hanging around Ai2 in Seattle🏔️
    33K
  • user avatar
    William Merrill
    @lambdaviking
    Feb 23, 2021
    I wrote an introduction to formal languages and automata as they relate to modern NLP (RNNs, transformers, etc.) Check it out on arXiv!
    arXiv logo
    arxiv.org
    Formal Language Theory Meets Modern NLP
    NLP is deeply intertwined with the formal study of language, both conceptually and historically. Arguably, this connection goes all the way back to Chomsky's Syntactic Structures in 1957. It also...
  • user avatar
    William Merrill
    @lambdaviking
    May 27, 2025
    Padding a transformer’s input with blank tokens (...) is a simple form of test-time compute. Can it increase the computational power of LLMs? 👀 New work with @Ashish_S_AI addresses this with *exact characterizations* of the expressive power of transformers with padding 🧵
    29K
  • user avatar
    William Merrill
    @lambdaviking
    Sep 27, 2022
    [1/6] Excited to share a year-long project re: theory of language understanding in LMs w/ @a_stadt, @tallinzen TLDR: Judging entailments (NLI) can be reduced to LMing over "Gricean data"* ∴ Learning distribution (perfectly) => learning semantics
    arXiv logo
    arxiv.org
    Entailment Semantics Can Be Extracted from an Ideal Language Model
    Language models are often trained on text alone, without additional grounding. There is debate as to how much of natural language semantics can be inferred from such a procedure. We prove that...
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    William Merrill
    @lambdaviking
    Apr 21, 2020
    A Formal Hierarchy of RNN Architectures -- in which we address questions like "what can an LSTM do that a QRNN can't?" Joint work with @gail_w, @yoavgo, @royschwartz02, @nlpnoah, and @yahave #acl2020nlp Blog: lambdaviking.com/post/rr-hierar… Paper: arxiv.org/abs/2004.08500
  • user avatar
    William Merrill
    @lambdaviking
    Apr 23, 2021
    Is it possible for GPT-n to "understand" the semantics of English? What about Python? I'm excited to finally share work formalizing this question! We give formal languages that are *provably* un-understandable by LMs (within our setup, at least) arxiv.org/abs/2104.10809
  • user avatar
    William Merrill
    @lambdaviking
    Oct 17, 2022
    How do we understand logical reasoning in non-symbolic models like transformers? 📣New preprint w/ Ashish Sabharwal shows any transformer can be translated to a fixed-size first-order-logic formulae (with majority quantifiers)
    arXiv logo
    arxiv.org
    A Logic for Expressing Log-Precision Transformers
    One way to interpret the reasoning power of transformer-based language models is to describe the types of logical rules they can resolve over some input text. Recently, Chiang et al. (2023) showed...
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    William Merrill
    @lambdaviking
    Feb 27, 2024
    📢 Preprint: We can predict entailment relations from LM sentence co-occurrence prob. scores These results suggest predicting sentence co-occurrence may be one way that next-word prediction leads to (partial) semantic representations in LMs🧵
    25K
  • user avatar
    William Merrill
    @lambdaviking
    Sep 13, 2021
    What inductive biases does training impose on transformers? We find that T5, RoBERTa, etc. are well-approximated by saturated transformers (simplified attention patterns), and explain how this arises during training. w/ @RamanujanVivek @yoavgo @royschwartzNLP @nlpnoah
  • user avatar
    William Merrill
    @lambdaviking
    Oct 20, 2019
    Better, faster stack neural networks (in PyTorch)!
    GitHub - viking-sudo-rm/stacknn-core: Pip-installable differentiable stacks in PyTorch!
    From github.com