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README.md
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---
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tags:
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- mixture-of-experts
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- moe
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- transformer
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- language-model
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- pytorch
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- conditional-computation
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datasets:
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- custom
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pipeline_tag: text-generation
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license: mit
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---
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# Mixture-of-Experts Language Models
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A PyTorch implementation exploring conditional computation in Transformers through Mixture-of-Experts (MoE).
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## Models
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This repository contains two MoE architectures:
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### 1. Sparse MoE (Top-K Routing)
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Routes each token to a fixed number of experts (k=2), increasing model capacity without proportionally increasing compute.
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### 2. Dynamic MoE (Confidence-Based Routing)
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Dynamically adjusts the number of experts per token based on routing confidence—"easy" tokens use fewer experts, "hard" tokens use more.
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## Model Details
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| Parameter | Sparse MoE | Dynamic MoE |
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|-----------|------------|-------------|
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| Layers | 4 | 4 |
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| Hidden Dim | 512 | 512 |
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| FFN Dim | 2048 | 2048 |
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| Attention Heads | 8 | 8 |
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| Experts | 8 | 4 |
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| Routing | Top-2 | τ=0.8 threshold |
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| Context Length | 256 | 256 |
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| Vocab Size | 10,000 | 10,000 |
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## Architecture
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```
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Input → Embedding → [Transformer Block × N] → RMSNorm → Linear → Output
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Transformer Block:
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└─ RMSNorm → Multi-Head Self-Attention → Residual
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└─ RMSNorm → MoE Layer → Residual
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MoE Layer:
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└─ Router (softmax gating)
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└─ Expert Selection (Top-K or Dynamic)
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└─ Weighted Expert Outputs
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```
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## Training
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Both models were trained with:
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- **Optimizer**: AdamW (β1=0.9, β2=0.95)
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- **Learning Rate**: 3e-4 with cosine decay
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- **Warmup Steps**: 2,000
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- **Weight Decay**: 0.1
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### Loss Functions
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**Sparse MoE:**
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```
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L = L_CE + α * L_balance
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```
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**Dynamic MoE:**
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```
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L = L_CE + β * L_balance + γ * L_entropy
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```
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Where:
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- `L_CE`: Cross-entropy loss
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- `L_balance`: Load balancing loss (encourages uniform expert utilization)
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- `L_entropy`: Entropy regularization (encourages sparse routing)
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## Usage
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```python
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import torch
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from moe.moelm import MoeLM, DynamicMOELM
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# Load Sparse MoE
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sparse_model = MoeLM(
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vocab_size=10000,
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num_layers=4,
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context_length=256,
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d_model=512,
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d_ff=2048,
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num_heads=8,
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num_experts=8,
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top_k=2
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)
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sparse_model.load_state_dict(torch.load("sparse_moe_final.pt"))
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# Load Dynamic MoE
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dynamic_model = DynamicMOELM(
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vocab_size=10000,
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num_layers=4,
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context_length=256,
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d_model=512,
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d_ff=2048,
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num_heads=8,
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num_experts=4,
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confidence_threshold=0.8
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)
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dynamic_model.load_state_dict(torch.load("dynamic_moe_final.pt"))
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```
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## Files
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| File | Description |
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|------|-------------|
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| `sparse_moe_final.pt` | Sparse MoE model weights |
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| `dynamic_moe_final.pt` | Dynamic MoE model weights |
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| `sparse_moe_config.json` | Sparse MoE configuration |
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| `dynamic_moe_config.json` | Dynamic MoE configuration |
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## Citation
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```bibtex
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@misc{moe-lm-2024,
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title={Mixture-of-Experts Language Model},
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author={Chaitanya},
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year={2024},
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url={https://github.com/chaitanya/transformers-and-MOE}
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}
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```
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## Reference
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Based on ["Harder Tasks Need More Experts: Dynamic Routing in MoE Models"](https://arxiv.org/abs/2403.07652)
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## License
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MIT
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