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What is text-llm-training-from-scratch?

y0oshi/text-llm-training-from-scratch — explained in plain English

Analysis updated 2026-05-18

30PythonAudience · developerComplexity · 4/5LicenseSetup · moderate

In one sentence

A from scratch, code first walkthrough of how to build and train a text generating AI model, step by step, in plain PyTorch.

Mindmap

mindmap
  root((repo))
    What it does
      Tokenizes text
      Pretrains model
      Fine tunes on instructions
      Aligns with preferences
    Tech stack
      Python
      PyTorch
      CUDA and MPS support
    Use cases
      Learn LLM internals
      Train a small demo model
      Experiment with alignment methods
    Audience
      Researchers
      Developers
      Students
    Example
      17M parameter model
      TinyStories dataset
      Coherent sample output
    Design
      Byte level tokenizer
      Memory mapped data
      Single command interface

Code map

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What do people build with it?

USE CASE 1

Learn exactly how a language model is trained by reading a full, unhidden implementation.

USE CASE 2

Train a small demonstration language model on the included tiny sample text corpus.

USE CASE 3

Experiment with fine tuning and preference based alignment techniques like DPO on your own data.

USE CASE 4

Reproduce a 17 million parameter model trained on short story text and compare results.

What is it built with?

PythonPyTorchNumPy

How does it compare?

y0oshi/text-llm-training-from-scratchav2xn/doanchandar-lab/semantic-wm
Stars303030
LanguagePythonPythonPython
Setup difficultymoderatehardhard
Complexity4/55/55/5
Audiencedeveloperdeveloperresearcher

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · moderate Time to first run · 30min

Requires Python 3.10+ and PyTorch 2.1+, a CUDA GPU speeds things up but CPU and Apple Silicon also work.

Use freely for any purpose, including commercial use, as long as you keep the copyright notice.

So what is it?

This project builds an entire text generating AI system from the ground up, in Python, without relying on the popular libraries that usually hide the details. Instead of using ready made frameworks like transformers, it writes every piece of the training process itself, so someone learning how these systems work can read through the code stage by stage and understand what is actually happening at each step. The pipeline covers four main phases: turning text into a numbered vocabulary the model can read, training the model to predict the next piece of text over and over, teaching it to follow instructions through supervised fine tuning, and then refining its behavior further using preference based methods that reward better responses over worse ones. The underlying model is a modern text transformer built with the same kinds of components used in current well known models, and it runs on a regular CPU, an Apple Silicon Mac, or an Nvidia GPU without needing separate code for each. Once installed, the project gives you a single command called llm that can train a tokenizer, prepare training data, pretrain a model, generate text from it, and more. It even includes a small sample text dataset so you can run through the whole process quickly, and an interactive menu that walks you through every step by arrow keys, always showing you the exact command it is about to run. As a concrete demonstration, the repo includes a ready made configuration for a small 17 million parameter model trained on a dataset of short children's stories, and shows a real sample of the coherent short stories that model can produce after training. The tokenizer works at the level of raw text bytes, so it can handle any language without ever failing to recognize a character, and training data is stored efficiently on disk so datasets larger than your computer's memory can still be used. This project is best suited for people who want to genuinely understand how language models are trained rather than just use one, and it is released under the MIT license.

Copy-paste prompts

Prompt 1
Walk me through running the quickstart commands to train a tiny language model from this repo.
Prompt 2
Explain how the byte level BPE tokenizer in this project turns raw text into tokens.
Prompt 3
Help me reproduce the 17 million parameter TinyStories model described in this README.
Prompt 4
Explain the difference between the supervised fine tuning stage and the DPO alignment stage here.

Frequently asked questions

What is text-llm-training-from-scratch?

A from scratch, code first walkthrough of how to build and train a text generating AI model, step by step, in plain PyTorch.

What language is text-llm-training-from-scratch written in?

Mainly Python. The stack also includes Python, PyTorch, NumPy.

What license does text-llm-training-from-scratch use?

Use freely for any purpose, including commercial use, as long as you keep the copyright notice.

How hard is text-llm-training-from-scratch to set up?

Setup difficulty is rated moderate, with roughly 30min to a first successful run.

Who is text-llm-training-from-scratch for?

Mainly developer.

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