Pebble-50M-beta

Pebble-50M-beta is an experimental 50M-parameter language model designed to test how a larger Pebble architecture performs with a 16,384-token vocabulary and 16,384-token context window.

Despite having roughly twice the parameters of Pebble-25M, Pebble-50M-beta underperformed Pebble-25M and, on some evaluations, Pebble-10M. This model is therefore primarily useful as an experimental result rather than as the strongest Pebble model.

Model Details

  • Architecture: Hybrid Mamba2 / Transformer
  • Block Pattern: 3 Mamba2 blocks : 1 Attention block (repeating)
  • Parameters: ~49,334,448 (50M)
  • Hidden Dimension: 768
  • Layers: 8 (6 Mamba2, 2 Attention)
  • Vocab Size: 16,384 (Custom Byte-Level BPE)
  • Context Length: 16,384
  • Training Tokens: 25,000,000,000 (25 Billion)
  • Optimizer: Muon (for 2D hidden weights) + AdamW (for embeddings, norms, and scalars)
  • Precision: fp32 master weights with bf16 autocast

Dataset Sources

The model was trained on a 25B-token subset of the following datasets:

Dataset Token Allocation Share
FineWeb-Edu 7.50 billion 30%
DCLM 5.00 billion 20%
Cosmopedia-v2 3.75 billion 15%
FineMath-4+ 3.75 billion 15%
FinePhrase 3.00 billion 12%
NPset 2.00 billion 8%
Total 25.00 billion 100%

Benchmarks

The original benchmark logs for this model were lost, so exact evaluation results are unavailable.

Qualitatively, Pebble-50M-beta underperformed Pebble-25M and, on some evaluations, Pebble-10M.

Usage

Pebble-50M-beta does not require the mamba-ssm library and is intended to be usable with standard PyTorch-based inference implementations.

It may run on CUDA GPUs, AMD GPUs, Intel GPUs, and CPUs depending on the inference framework and available hardware acceleration.

Status

This is a beta/experimental model. It is primarily intended for research and experimentation with the Pebble architecture.

License

Apache 2.0

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