Bochkov/growing-transformers-model-unfrozen-1-9-247m

Growing Transformers — Model unfrozen 1_9 (≈247M)

This repository contains growing-transformers-model-unfrozen-1-9-247m, a constructively grown (layer-wise expanded) model from the paper:

📚 Paper (Growing Transformers: Modular Composition and Layer-wise Expansion on a Frozen Substrate) -

📚 Paper (Emergent Semantics Beyond Token Embeddings: Transformer LMs with Frozen Visual Unicode Representations) -

It is part of the comparative-study collection:
https://huggingface.co/collections/Bochkov/growing-transformers-layer-wise-expansion-comparative-study

Code:
https://github.com/AVBochkov/PGT

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What this model is (in one paragraph)

This is a 9-layer decoder-only Transformer trained with a constructive, layer-wise growth procedure (layers are added and trained progressively while previously trained parts are frozen). Unlike the “frozen-substrate” variants, this model starts with standard trainable token embeddings and is trained monolithically for the first stage (layers 1–3 + embeddings all trainable). After that first stage converges, the embedding layer and the first 3 layers are frozen, then layers 4–6 are trained, frozen, and finally layers 7–9 are trained. This model exists to isolate the effect of the growth procedure without a frozen embedding substrate at initialization.

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Main comparison (why this repo exists)

This model is intended to be compared primarily against:

• Bochkov/growing-transformers-model-16-bit-1-9-181m (constructive growth, frozen 16-bit embedding)
• Bochkov/growing-transformers-model-unicode-1-9-247m (constructive growth, frozen “visual UNICODE” embedding)

All these models share the same Transformer stack design in the controlled study (same depth and same d_model / n_head), but differ in the embedding substrate and what is frozen when.

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Important: parameter count difference (why this model is larger than 16-bit)

This checkpoint is larger (≈247M parameters) than the 16-bit constructive model (≈181M) primarily because it uses a full-size embedding matrix (standard learned embeddings at d_model, with vocab_size = 65,536), whereas the 16-bit model uses a tiny n_embed = 16 embedding that is deterministically expanded to d_model.

Even with the same Transformer blocks, the embedding matrix dominates a large chunk of parameters when vocab_size is large and n_embed = d_model.

Note: exact parameter totals can differ slightly across implementations (e.g., weight tying vs separate LM head). The key reason for the size gap is the embedding dimensionality (full d_model vs 16).

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Training method (constructive growth schedule)

This model was trained in three stages (controlled study setup):

1. Stage A (classic / unfrozen start): train token embeddings + layers 1–3 (all trainable)
2. Stage B: freeze embeddings + layers 1–3, add layers 4–6, train only layers 4–6
3. Stage C: freeze embeddings + layers 1–6, add layers 7–9, train only layers 7–9

So: it is constructive / iterative, but not “frozen embeddings Stage A”.

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Model architecture (controlled study)

• Type: decoder-only Transformer (GPT-like)
• Layers: 9
• Hidden size: d_model = 1024
• Heads: n_head = 32
• Context length used in training: 1024
• Embedding: standard learned embedding matrix (trainable in Stage A, frozen afterwards)

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Tokenizer

This model uses the BVV tokenizer. Canonical tokenizer repo:

• https://huggingface.co/Bochkov/bvv241-2-3
  (collection: https://huggingface.co/collections/Bochkov/tokenizers)

Reproducibility note: even with the same tokenizer, this repo also includes embedding artifacts specific to this model, so for exact reproduction it is recommended to load the tokenizer from this model repo.

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How to use (Transformers)

import torch
from transformers import AutoTokenizer, AutoModelForCausalLM

tokenizer = AutoTokenizer.from_pretrained("Bochkov/growing-transformers-model-unfrozen-1-9-247m")
model = AutoModelForCausalLM.from_pretrained("Bochkov/growing-transformers-model-unfrozen-1-9-247m", trust_remote_code=True).to('cuda')

inputs = torch.tensor([tokenizer.encode("Write a short poem about the ocean. ")], dtype=torch.long, device='cuda')

outputs = model.generate(
    inputs, 
    max_new_tokens=50,
    do_sample=False
)
print(tokenizer.decode(outputs[0].tolist()))
#Write a short poem about the ocean. The poem was written by the author of the poem The Lord of the Rings, and was published in 

inputs = torch.tensor([tokenizer.encode("Question: What is the capital of India?\nAnswer:")], dtype=torch.long, device='cuda')

outputs = model.generate(
    inputs, 
    max_new_tokens=10,
    do_sample=False
)
print(tokenizer.decode(outputs[0].tolist()))
#Question: What is the capital of India?
#Answer:San Francisco de Pa

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🧑‍🔬 Citation & Concept

If you use this model or the underlying concepts in your research, please cite our work:

@article{
      bochkov2025emergent,
      title={Emergent Semantics Beyond Token Embeddings: Transformer {LM}s with Frozen Visual Unicode Representations},
      author={Andrey Bochkov},
      journal={Transactions on Machine Learning Research},
      issn={2835-8856},
      year={2025},
      url={https://openreview.net/forum?id=Odh8IynO1o},
      note={}
}

@misc{bochkov2025growingtransformersmodularcomposition,
      title={Growing Transformers: Modular Composition and Layer-wise Expansion on a Frozen Substrate}, 
      author={A. Bochkov},
      year={2025},
      eprint={2507.07129},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2507.07129}, 
}