Create README.md
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README.md
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# Diffusion LM — TinyStories
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A masked-diffusion language model trained from scratch on the
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[TinyStories](https://huggingface.co/datasets/roneneldan/TinyStories) dataset.
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## Demo
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## Architecture
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| Param | Value |
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|---|---|
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| Parameters | ~45M |
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| Hidden dim | 512 |
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| Layers | 10 |
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| Heads | 8 |
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| FFN dim | 2048 |
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| Diffusion steps T | 128 |
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| Sequence length | 256 |
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| Vocab size | 26,000 |
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## How it works
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This is a **masked diffusion** language model. Instead of generating
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tokens left-to-right like a standard LM, it starts with a fully masked
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sequence and progressively unmasks tokens over T diffusion steps.
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At each step the model predicts all masked tokens simultaneously, then
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re-masks the least confident predictions and repeats — gradually
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refining the output until the sequence is fully unmasked.
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## Training
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- Dataset: 1M TinyStories examples
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- Train steps: 60,000
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- Effective batch size: 64 (batch 32 × grad accum 2)
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- Optimizer: AdamW
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- Learning rate: 2e-4 with cosine schedule and 1,000 warmup steps
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- Weight decay: 0.1
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- Mixed precision: bf16
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- Hardware: NVIDIA RTX 3090 (24GB)
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## Evaluation
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Val loss (cross-entropy on masked tokens, 20 batches of held-out TinyStories):
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| Step | Val Loss |
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|------|----------|
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| 5,000 | 6.0313 |
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| 10,000 | 5.9045 |
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| 15,000 | 5.6092 |
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| 20,000 | 4.4481 |
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| 25,000 | 3.8447 |
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| 30,000 | 3.6634 |
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| 35,000 | 3.5419 |
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| 40,000 | 3.3554 |
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| 45,000 | 3.2779 |
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| 50,000 | 3.1767 |
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| 55,000 | 3.1012 |
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| 60,000 | 3.1067 |
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The loss drop between steps 15,000–25,000 reflects the model learning
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basic language structure. Convergence around 3.10 by step 55,000.
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## Files
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| File | Description |
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|---|---|
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| `model.pt` | Model weights (PyTorch state dict) |
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| `config.json` | Architecture hyperparameters |
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| `tokenizer/` | Byte-level BPE tokenizer |
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| `val_loss_history.json` | Validation loss curve |
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| `inference.gif` | Visualisation of progressive unmasking |
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