CMBA-768M-FineWeb

A 768M parameter Hierarchical Recurrent Memory (HRM) language model trained on high-quality web text from FineWeb-Edu. This model uses Mamba2 state-space models instead of traditional attention mechanisms, enabling efficient long-range sequence modeling.

Model Architecture

CMBA (Causal Mamba-based Architecture) implements a hierarchical processing structure:

• Hierarchical Design: Dual-level processing with H-layers (high-level abstraction) and L-layers (low-level specialists)
• Mamba2 Mixers: State-space models replace attention for O(n) complexity vs O(n²)
• Adaptive Computation: Halting mechanism allows variable compute per token (ACT-style pondering)
• Parameters: ~768M total
• Context Length: 1024 tokens

Configuration

Model Dimensions:
  - d_model: 768
  - n_heads: 12 (for compatibility, not used in Mamba)
  - d_ff: 3072
  - H_layers: 12 (high-level hierarchy)
  - L_layers: 12 (low-level processing)

Mamba2 Settings:
  - d_state: 128
  - expand: 2
  - headdim: 64
  - d_conv: 4
  - ngroups: 1

Training:
  - Max halt steps: 8
  - Block size: 1024
  - Batch size: 32 (effective)
  - Learning rate: 0.0002 → 1e-06
  - Weight decay: 0.1

Training Data

• Dataset: HuggingFaceFW/fineweb-edu (sample-10BT)
• Tokenizer: t5-small (T5 SentencePiece)
• Vocab Size: 32100

Latest Performance (Epoch 2)

• Validation Loss: 8.1216
• Validation Perplexity: 3366.37

Usage

from transformers import T5Tokenizer
from hrm_text1_modeling import HRMText1

tokenizer = T5Tokenizer.from_pretrained("t5-small")
model = HRMText1.from_pretrained("Viharikvs/CMBA-768M-FineWeb")

# Generate text
input_ids = tokenizer("Once upon a time", return_tensors="pt").input_ids
outputs = model.generate(input_ids, max_length=100)
print(tokenizer.decode(outputs[0]))

Citation

If you use this model, please cite:

@misc{cmba-768m-fineweb,
  author = {Vihari},
  title = {CMBA-768M-FineWeb: Hierarchical Mamba-based Language Model},
  year = {2025},
  publisher = {HuggingFace},
  url = {https://huggingface.co/Viharikvs/CMBA-768M-FineWeb}
}

License

Apache 2.0