Speculative Decoding Implementations: EAGLE-3, Medusa-1, PARD, Draft Models, N-gram and Suffix Decoding from scratch [P]

I’ve been working on an educational implementation repo for speculative decoding:

https://github.com/shreyansh26/Speculative-Decoding

The goal is not to wrap existing libraries, but to implement several speculative decoding methods from scratch behind a shared decoding/evaluation contract so that the differences between proposer designs are easier to study.

Implemented methods so far:

• EAGLE-3
• Medusa-1
• standard draft model speculation
• PARD / parallel draft models
• n-gram prompt lookup
• suffix decoding

The repo has both training and inference paths where applicable. For learned proposers, I use Qwen/Qwen2.5-7B-Instruct as the target model and small learned/speculative heads or draft models, depending on the method. For training-free methods, the proposer is built from the prompt/generated context.

A few things I wanted the repo to make explicit:

1. The distinction between proposer quality and verifier cost.
2. Why a high acceptance rate does not always imply higher throughput.
3. Why methods like PARD can be faster despite lower acceptance than an autoregressive draft model.
4. How EAGLE/Medusa-style learned heads differ from draft-model speculation.
5. How simple methods like n-gram and suffix decoding behave when the prompt contains a reusable structure.

The repo includes benchmark summaries, command lines, checkpoints/exports, and implementation notes. Some results are intentionally on small train-overlap eval slices due to compute constraints, so I would treat the numbers as implementation/behavioral benchmarks rather than broad generalization claims.

I built this mostly as a learning resource for people who want to understand speculative decoding at the algorithm + systems boundary: how the proposer is trained, how draft tokens are generated, how target verification works, what gets cached, and where the speedups actually come from.