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Decoding the Decoder LLM without de code: Ishan Anand
Takeaway
You can fully understand a decoder LLM by stepping through GPT-2 small implemented as a 124M-cell Excel sheet — no code required.
Summary
- Ishan Anand teaches the full GPT-2 small architecture via an Excel spreadsheet implementing all 124M parameters across 150+ tabs using only built-in spreadsheet functions — no Python, no APIs.
- Walks through anatomy (tokenization, embeddings, multi-head attention, MLP, probability output) by literally tracing cells in the workbook.
- Demonstrates BPE-style tokenization on invented words like 'funology' splitting into 'fun' + 'ology' to show subword morpheme behavior.
- Performs 'AI brain surgery' by editing the spreadsheet's weights/activations to change model behavior — making the math viscerally tangible to non-ML engineers.
educationgpt-2transformers
Original description
Spreadsheets are all you need: Decoding the Decoder LLM without de code The struggle to grasp the inner workings of AI models can leave even experienced engineers from non-ML backgrounds feeling lost in a sea of terminology and new concepts. What if the key to understanding the intricate mechanics of LLMs didn't require a Ph.D.? This session offers an innovative approach, employing spreadsheets to dissect and demystify the architecture of decoder-based LLMs using a fully working implementation of GPT-2 entirely in Excel. Attendees will tour through GPT-2's architecture from tokenization, embeddings, attention, multi-layer perceptron, all translated into the accessible format of spreadsheets with minimal abstractions to get in the way. By the end, you'll gain unparalleled insights into AI's backbone, transforming abstract concepts into tangible, understandable processes, without ever touching code. Recorded live in San Francisco at the AI Engineer World's Fair. See the full schedule of talks at https://www.ai.engineer/worldsfair/2024/schedule & join us at the AI Engineer World's Fair in 2025! Get your tickets today at https://ai.engineer/2025 About Ishan Ishan was most recently VP of Product for Edgio Applications, a platform that leverages edge computing, serverless, and AI/ML to enable enterprise teams to accelerate, host, and secure their high-stakes websites. Ishan joined Edgio via the acquisition of Layer0, where he was the CTO and co-founder. He's also the creator of Spreadsheets-are-all-you-need.ai which combines AI and Spreadsheets into a course that teaches how LLMs work through an implementation of GPT2 (an ancestor of ChatGPT) entirely in Excel. Ishan spoken at conferences such as JSMobile, Next.js, JSWorld, and React Day New York on web performance, Jamstack, and Core Web Vitals.