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Charles Foster
6,412 posts
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Charles Foster
@CFGeek
Excels at reasoning & tool use🪄 Tensor-enjoyer 🧪 @METR_Evals. My COI policy is available under “Disclosures” at contextwindows.substack.com/about
Oakland, CA
contextwindows.substack.com
Joined June 2020
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  • Pinned
    user avatar
    Charles Foster
    @CFGeek
    May 22, 2023
    Running list of conjectures about neural networks 📜:
    42K
  • user avatar
    Charles Foster
    @CFGeek
    Feb 28, 2025
    If you’re bored with today’s neural net architectures, then my advice to you is to start training models to use an external memory, now that RL is finally working.
    60K
  • user avatar
    Charles Foster
    @CFGeek
    Mar 27, 2023
    The normalization scheme that DeepMind researchers came up with for their "linear recurrent unit" (LRU) is a nice example of how it is possible to predictably engineer circuits in artificial neural networks, when you know what you're doing. A thread:
    Image from the preprint "Resurrecting Recurrent Neural Networks for Long Sequences", with normalization term highlighted and question marks next to it
    151K
  • user avatar
    Charles Foster
    @CFGeek
    Oct 19, 2025
    Just read their paper. Looks like they re-invented an existing method known as context distillation (or merely re-branded it for their startup). No mention of prior work, sadly. Links to papers in thread.
    user avatar
    Bread
    @ai_bread
    Oct 18, 2025
    Announcing Bread Technologies. We’re building machines that learn like humans. We raised a $5 million seed round led by Menlo Ventures and have been building in stealth for 10 months. Today, we rise 🍞
    00:00
    91K
  • user avatar
    Charles Foster
    @CFGeek
    Oct 7, 2025
    We're working on it!
    user avatar
    Lisan al Gaib
    @scaling01
    Oct 5, 2025
    guys pleeease I need to see Sonnet 4.5 on this
    69K
  • user avatar
    Charles Foster
    @CFGeek
    Jul 10, 2025
    Before you say “this isn’t surprising”… Yes, it is. We got people to preregister their expectations, and even folks who are extremely in-the-know about AI coding abilities still failed to predict this result. Your *vibes* are not reliable indicators of productivity effects.
    user avatar
    METR
    @METR_Evals
    Jul 10, 2025
    We ran a randomized controlled trial to see how much AI coding tools speed up experienced open-source developers. The results surprised us: Developers thought they were 20% faster with AI tools, but they were actually 19% slower when they had access to AI than when they didn't.
    24K
  • user avatar
    Charles Foster
    @CFGeek
    Nov 4, 2025
    METR: “What is my purpose?” ALL: “You put new AI models on The Graph.” METR: “Oh my god...”
    user avatar
    Lisan al Gaib
    @scaling01
    Oct 5, 2025
    guys pleeease I need to see Sonnet 4.5 on this
    55K
  • user avatar
    Charles Foster
    @CFGeek
    Apr 9, 2024
    YES! If you initialize a LoRA layer based on the SVD of the original weight matrix (with its top singular values & vectors), you get significantly better fine-tuning results. This is a straight-up free lunch, as far as I can tell.
    user avatar
    Aran Komatsuzaki
    @arankomatsuzaki
    Apr 8, 2024
    PiSSA: Principal Singular Values and Singular Vectors Adaptation of Large Language Models Significantly improved finetuned perf by simply changing the initialization of LoRA's AB matrix from Gaussian/zero to principal components of W repo: github.com/GraphPKU/PiSSA abs:
    32K
  • user avatar
    Charles Foster
    @CFGeek
    Dec 9, 2023
    What excites me most about the rising tide of RNNs/SSMs is that it could let the fields of machine learning and computational neuroscience use the same modeling tools.
    Figure from "Attractor and integrator networks in the brain". Link: https://www.nature.com/articles/s41583-022-00642-0
    59K
  • user avatar
    Charles Foster
    @CFGeek
    Oct 5, 2023
    Note: sparse coding is an *established* method for disentangling representations. Anthropic did not invent it, nor did they claim to. If their new results seem surprising, now's a great time to revisit the older literature (Olshausen, Kanerva, etc.).
    Diagram showing sparse coding with an overcomplete basis set, from Olshausen & Field, 1997. Link: https://www.sciencedirect.com/science/article/pii/S0042698997001697
    35K
  • user avatar
    Charles Foster
    @CFGeek
    Mar 1, 2024
    Wow! Papers from two different teams—one from academia and one from Google DeepMind—with the same finding: linear recurrence + local (sliding window) attention is your best bet if you want an efficient alternative to global attention.
    user avatar
    AK
    @_akhaliq
    Mar 1, 2024
    Simple linear attention language models balance the recall-throughput tradeoff Recent work has shown that attention-based language models excel at recall, the ability to ground generations in tokens previously seen in context. However, the efficiency of attention-based models is
    34K
  • user avatar
    Charles Foster
    @CFGeek
    Jul 29, 2023
    Stability changed the name of these models to "Stable Beluga 1/2" and quietly removed the sentence of the blog post that mentioned they used two unnamed LLMs to generate their dataset. (This likely means they used OpenAI models, in clear violation of ToS) web.archive.org/web/2023072122…
    user avatar
    Charles Foster
    @CFGeek
    Jul 21, 2023
    @EMostaque @lcastricato
    Goose chasing man meme, with "Which LLMs did you generate those examples with?... Which LLMs generated your dataset, [blurred expletive]?!" and a screenshot from the blog post this is responding to, with a quote displayed reading "With this approach, we generated 500,000 examples with one simpler LLM model and an additional 100,000 with a more sophisticated LLM model."
    89K
  • user avatar
    Charles Foster
    @CFGeek
    Oct 31, 2025
    We put the model in a test and then we steer the model away from thinking “I am in a test” and then we steer the model away from introspecting “I am being steered away from thinking «I am in a test»”
    user avatar
    Tim Hua 🇺🇦
    @Tim_Hua_
    Oct 30, 2025
    Problem: AIs can detect when they are being tested and fake good behavior. Can we suppress the “I’m being tested” concept & make them act normally? Yes! In a new paper, we show that subtracting this concept vector can elicit real-world behavior even when normal prompting fails.
    32K
  • user avatar
    Charles Foster
    @CFGeek
    Mar 6, 2025
    A short thread of news 🧵 (1/3) I’ve joined the policy team at METR! Rapid AI changes will require measuring & addressing potential new threats far more quickly.
    11K