如何微调GitHub Copilot？

Question

We can fine tune language models like BERT , GPT-3 .

Can I fine tune GitHub Copilot model?

I have already looked into examples from https://copilot.github.com/ but cant find the details.

Would really appreciate if someone had fine tuned Github Copilot.

Answer 1

There does not seem to be a client-facing feature allowing you to fine-tune Copilot directly.

Here are two illustration as to why this feature is, for now (Q2 2022) missing.

The Copilot feature page initially included this:

How will GitHub Copilot get better over time?

GitHub Copilot doesn't actually test the code it suggests, so the code may not even compile or run. GitHub Copilot can only hold a very limited context, so even single source files longer than a few hundred lines are clipped and only the immediately preceding context is used. And GitHub Copilot may suggest old or deprecated uses of libraries and languages. You can use the code anywhere, but you do so at your own risk.

As Tomek Korbak explains on Twitter :

Actually, Copilot's completions will always be optimised for human's liking, not necessarily compiler's liking.

That's because the language model training objective (predicting the next token in text) is great at capturing short-term dependencies (which explains the human feel of generated snippets).

But it struggles to capture long-term, global, semantic properties of generated sequences such as compilability. And there's no easy way of including compilability as a signal for their training.

The standard way -- fine-tuning language models using RL with compilability as a reward -- notoriously leads to catastrophic forgetting: less diverse and less accurate completions.

Tomek references " Energy-Based Models for Code Generation under Compilability Constraints (pdf) "

Our solution (KL-DPG) boosts compilability rate of generated sequences from 55% to 70%.
RL fine-tuning can do better but at a cost of catastrophic forgetting.

Overall, energy-based models (EBMs) turn out to be great at expressing weird, sequence-level constraints that would be super hard as to express as normalised priors for autoregressive language models.

EBMs provide a way of injecting our structured, symbolic knowledge into large language models without breaking them down or sacrificing their uncanny abilities.
The space of further applications in controllable generation is huge.

So not so easy.

Tanishq Mathew Abraham explains in " Coding with GitHub Copilot "

I wonder if the GitHub team might also develop a way of perhaps fine-tuning GitHub Copilot to specific use-cases.

For example, there may be a specific GitHub Copilot models for fastai, JAX, etc. They would be fine-tuned on the source code of of these libraries and codebases that use these libraries.

But making sure that the tool does not provide outdated suggestions would still be a challenge.
I don't think it would be possible to provide suggestions for a brand-new library that does not have enough codebases using it to train on.

Additionally, for situations like fastai where there are older APIs and newer APIs, when fine-tuning a model, the codebases using the older APIs would have to be filtered out.

Answer 2

OpenAI API offers the "Davinci Codex" machine learning model with a pay-per-hit subscription, similar to the the non-coding version of the davinci model.

OpenAI should enable the fine-tuning option to Davinci Codex as well. When they do it you will be able to use it via API calls.

After checking that prerequisite, I think you could link the OpenAI API to your local installation of Github Copilot via some code changes, in theory that should be possible.

The first step is probably to have a fork of the copilot VSCode extension that calls the OpenAI Codex API (or an entirely custom extension which inserts text in your code)

Then you would point it to your fine-tuned version of the model. To learn about fine-tuning OpenAI models you should look at their documentation:

• https://beta.openai.com/docs/guides/fine-tuning

Note that they have also a openai CLI that allows you to do most of the data loading and fine tuning tasks.

Unfortunately at the moment you can only fine tune the non-coding version of OpenAI models, hope that they will make available Codex soon.

Answer 3

No, not at all. There is no storing of GitHub Pilot's model in the client's system and also no access is provided to the model since now they have started charging for their services hence making it more obvious that their project isn't and won't be open-sourced.