---
license: cc-by-nc-4.0
language:
- en
pipeline_tag: text-classification
tags:
- pytorch
- reward_model
- transformers
- RLHF
---

This is part of the Chai reward-model series, using the GPT2 architecture with a classification head, optimising for a user accepting the completion generated by the base model.

Its training dataset consists of purely user-generated content [retry_and_continue_50m_reward_model](https://huggingface.co/datasets/ChaiML/retry_and_continue_50m_reward_model), where a user has the option to decline the generated response via the retry button or end the conversation.

## Model details
- Developed by [Chai Research](https://www.chai-research.com/)
- Model type: Transformer-based Classification Model
- Language: English
- License: cc-by-nc-4.0
- Contact: for general correspondence, please email [hello@chai-research.com](mailto:hello@chai-research.com?subject=Huggingface%20Model%20Inquiry)

## Uses and limitations
### Intended use
This reward model was developed primarily for commercial purposes. It learns an inner representation of response quality rated by humans that can be used to conduct best-of-N sampling and Reinforcement Leanring with the PPO framework.

In addition to scientific uses, you may also further fine-tune and adapt this reward model for deployment, as long as your use is in accordance with the cc-by-nc-4.0 license, i.e. non-commercial use. This model works with the Transformers Library. If you decide to this pre-trained reward model as a basis for your fine-tuned model, please note that you need to conduct your own risk and bias assessment.

### Out-of-scope use

This reward model is **not** intended for deployment as-is. It is not a product and cannot be used for human-facing interactions without supervision.

This model **has not** been optimised for common reward-model objectives such as harmfulness, truthfulness and helpfulness, it is only trained based on user actions present on the Chai mobile app platform. Therefore, this model will **not** rank responses appropriately when evaluating on common open-sourced datasets. All base model responses within the training data were generated using an in-house variant of [GPT-J](https://huggingface.co/EleutherAI/gpt-j-6B), therefore the model performance may degrade when the input is generated using other language models.

### How to use

This reward model can be loaded using the `AutoModelForSequenceClassification` functionality, with a GPT2 tokenizer where the `pad_token_id` is set to the EOS token id, padding sides need to be set according to the configurations used during model training.
```python
from transformers import AutoTokenizer, AutoModelForSequenceClassification

tokenizer = AutoTokenizer.from_pretrained("gpt2")
model = AutoModelForSequenceClassification.from_pretrained("ChaiML/gpt2_base_retry_and_continue_5m_reward_model")
tokenizer.pad_token_id = 50256
tokenizer.truncation_side = ‘left’
tokenizer.padding_side = ‘right’
tokens = self.eval_tokenizer(candidates, return_tensors='pt', return_attention_mask=True, padding='longest', truncation=True, max_length=256)
reward = model(**tokens).logits
```