---
license: apache-2.0
language:
  - en
tags:
  - mamba
  - ssm
  - transformer
  - text-generation
  - hybrid
library_name: pytorch
pipeline_tag: text-generation
---

# ALTAMBA 1.78B

**ALTAMBA** (Alternating Mamba) is a 1.78B parameter dual-path language model that runs a Transformer and State Space Model (Mamba-2) in parallel at every layer, blending them through learned destructive and constructive interference.

## Architecture

| Parameter | Value |
|-----------|-------|
| Parameters | 1.78B |
| Layers | 12 |
| d_model | 2560 |
| Attention heads | 8 |
| FFN expansion | 4x |
| Denoiser scale | 0.75x |
| Context length | 256 |
| Vocab size | 100,288 |
| Tokenizer | tiktoken cl100k_base |

### Key Innovations

- **Dual-path**: Transformer + Mamba-2 SSM run in parallel at every layer
- **Peristaltic Normalization**: Alternating Post-LayerNorm (even layers, variance clamping for denoising) and Pre-LayerNorm (odd layers, gradient flow for blending)
- **The Razor**: Learnable blending operation `y = s * [(c - W1) * LN(x_denoiser) + (c' - W2) * x_main]` with per-layer parameters and output scaling
- **Role reversal**: Even layers use SSM as main signal / Transformer as denoiser; odd layers reverse roles
- **Bottleneck compression**: 0.75x denoiser paths for parameter efficiency
- **Bounded-dt fix**: Sigmoid-bounded discretization timestep for Mamba-2 stability

## Results

| Scale | Baseline Val Loss | ALTAMBA Val Loss | Improvement |
|-------|-------------------|------------------|-------------|
| 402M  | 3.1866            | 2.8886           | 9.35%       |
| 1.08B | 2.9771            | 2.6974           | 9.40%       |
| 1.78B | 2.4427            | 2.2554           | 7.66%       |

Baselines are parameter-matched Jamba (1:7 attention-to-Mamba ratio). Trained on Common Pile (arXiv subset).

## Checkpoint Details

- **File**: `best_model_altamba_fp16.pt`
- **Format**: PyTorch state dict (fp16)
- **Training step**: 8625
- **Validation loss**: 2.2554
- **State dict keys**: Direct `TransformerSSMDenoise` keys (no wrapper prefix)

## Usage

```python
import torch
import tiktoken
from transformer_ssm_denoise import TransformerSSMDenoise

# Tokenizer
enc = tiktoken.get_encoding("cl100k_base")
vocab_size = 100288

# Create model
model = TransformerSSMDenoise(
    vocab_size=vocab_size,
    d_model=2560,
    n_layers=12,
    n_heads=8,
    d_ff=10240,
    dropout=0.0,
    init_w1=1.5,
    init_w2=-0.5,
    use_denoising=True,
    baseline_type="dual",
    use_scaling=True,
    denoiser_scale_ssm=0.75,
    denoiser_scale_transformer=0.75,
    use_odd_ssm=True,
)

# Load checkpoint
state_dict = torch.load("best_model_altamba_fp16.pt", map_location="cpu", weights_only=True)
model.load_state_dict(state_dict)
model.half().eval().cuda()

# Generate
prompt = "The fundamental theorem"
tokens = enc.encode(prompt)
input_ids = torch.tensor([tokens], dtype=torch.long, device="cuda")

with torch.no_grad():
    for _ in range(100):
        logits = model(input_ids[:, -512:])
        next_logits = logits[:, -1, :] / 0.8
        probs = torch.softmax(next_logits, dim=-1)
        next_token = torch.multinomial(probs, num_samples=1)
        input_ids = torch.cat([input_ids, next_token], dim=1)

print(enc.decode(input_ids[0].tolist()))
```

## Dependencies

- PyTorch >= 2.1.0
- [mamba-ssm](https://github.com/state-spaces/mamba) (requires CUDA)
- tiktoken

Architecture code available at [github.com/altamba/altamba](https://github.com/altamba/altamba).

## Training Configuration

- **Optimizer**: AdamW (lr=1e-4, cosine annealing)
- **Batch size**: 8 (gradient accumulation 8, effective 64)
- **Precision**: BF16 mixed precision
- **Gradient clipping**: 1.0
- **Dropout**: 0.2
- **Hardware**: NVIDIA RTX PRO 6000 Blackwell Server Edition (96GB)

## Citation

```bibtex
@article{seto2026altamba,
  title={ALTAMBA: Alternating Mamba with Peristaltic Normalization},
  author={Seto, Scott},
  year={2026},
  doi={10.5281/zenodo.18521311}
}
```

## License

Apache 2.0