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---
license: mit
datasets:
- openai/summarize_from_feedback
- openai/webgpt_comparisons
- Dahoas/instruct-synthetic-prompt-responses
- Anthropic/hh-rlhf
- lmsys/chatbot_arena_conversations
- openbmb/UltraFeedback
metrics:
- accuracy
tags:
- pair-ranker
- pair_ranker
- reward_model
- reward-model
- pairrm
- pair-rm
- RLHF
language:
- en
---

Inspired by [DeBERTa Reward Model Series](https://huggingface.co/OpenAssistant/reward-model-deberta-v3-large-v2) 
`llm-blender/PairRM` is pairranker version finetuned specifically as a reward model using deberta-v3-large. 

- Github: [https://github.com/yuchenlin/LLM-Blender](https://github.com/yuchenlin/LLM-Blender)
- Paper: [https://arxiv.org/abs/2306.02561](https://arxiv.org/abs/2306.02561)
- Space Demo: [https://huggingface.co/spaces/llm-blender/LLM-Blender](https://huggingface.co/spaces/llm-blender/LLM-Blender)


## Statistics

### Context length
|  PairRanker type  | Source max length | Candidate max length | Total max length |
|:-----------------:|:-----------------:|----------------------|------------------|
| [pair-ranker](https://huggingface.co/llm-blender/pair-ranker)               | 128               | 128                  | 384              |
| [PairRM](https://huggingface.co/llm-blender/pair-reward-model/) (This model) | 1224              | 412                  | 2048             |

## Usage Example

### Installation
Since PairRanker contains some custom layers and tokens. We recommend use PairRM with our llm-blender code API.
- First install `llm-blender`
```bash
pip install git+https://github.com/yuchenlin/LLM-Blender.git
```

- Then load pairranker with the following code:
```python
import llm_blender
blender = llm_blender.Blender()
blender.loadranker("llm-blender/PairRM") # load PairRM
```

### Use case 1: Compare responses (Quality Evaluator)

- Then you can rank candidate responses with the following function

```python
inputs = ["input1", "input2"]
candidates_texts = [["candidate1 for input1", "candidatefor input1"], ["candidate1 for input2", "candidate2 for input2"]]
ranks = blender.rank(inputs, candidates_texts, return_scores=False, batch_size=2)
# ranks is a list of ranks where ranks[i][j] represents the ranks of candidate-j for input-i
```

- Directly compare two candidate responses
```python
candidates_A = [cands[0] for cands in candidates]
candidates_B = [cands[1] for cands in candidates]
comparison_results = blender.compare(inputs, candidates_A, candidates_B)
# comparison_results is a list of bool, where element[i] denotes whether candidates_A[i] is better than candidates_B[i] for inputs[i]
```

- Directly compare two multi-turn conversations given that user's query in each turn are fiexed and responses are different.
```python
conv1 = [
    {
        "content": "hello",
        "role": "USER"
    },
    {
        "content": "<assistant response>",
        "role": "ASSISTANT"
    },
    ...
]
conv2 = [
    {
        "content": "hello",
        "role": "USER"
    },
    {
        "content": "<assistant response>",
        "role": "ASSISTANT"
    },
    ...
]
comparison_results = blender.compare_conversations([conv1], [conv2])
# comparison_results is a list of bool, where each element denotes whether all the responses in conv1 together is better than that of conv2
```

### Use case 2: Best-of-n sampling (Decoding Enhancing)
**Best-of-n Sampling**, aka, rejection sampling, is a strategy to enhance the response quality by selecting the one that was ranked highest by the reward model (Learn more at[OpenAI WebGPT section 3.2](https://arxiv.org/pdf/2112.09332.pdf) and [OpenAI Blog](https://openai.com/research/measuring-goodharts-law)). 

Best-of-n sampling is a easy way to imporve your llm power with just a few lines of code. An example of applying on zephyr is as follows.

```python
from transformers import AutoTokenizer, AutoModelForCausalLM

tokenizer = AutoTokenizer.from_pretrained("HuggingFaceH4/zephyr-7b-beta")
model = AutoModelForCausalLM.from_pretrained("HuggingFaceH4/zephyr-7b-beta", device_map="auto")

inputs = [...] # your list of inputs
system_message = {
    "role": "system",
    "content": "You are a friendly chatbot who always responds in the style of a pirate",
}
messages = [
    [   
        system_message,
        {"role": "user", "content": _input},
    ]
    for _input in zip(inputs)
]
prompts = [tokenizer.apply_chat_template(m, tokenize=False, add_generation_prompt=True) for m in messages]
outputs = blender.best_of_n_generate(model, tokenizer, prompts, n=10)
print("### Prompt:")
print(prompts[0])
print("### best-of-n generations:")
print(outputs[0])
```

### Use case 3: RLHF 
PairRM has been trained on various high-quality and large-scale dataset with human preference annotations and exhibits great correlation with human preferences with an extremly small model size (0.4B), approching the performance of GPT-4. 
We believe PairRM will power the alignment of LLM in an efficient and effective way.
With a `blender.compare()` function, you can easily apply PairRM to poopular RLHF toolkits like [trl](https://huggingface.co/docs/trl/index). 

**🔥 Check more details on our example jupyter notebook usage: [`blender_usage.ipynb`](https://github.com/yuchenlin/LLM-Blender/blob/main/blender_usage.ipynb)**


Learn more in our LLM-Blender Github [README.md](https://github.com/yuchenlin/LLM-Blender#rank-and-fusion)

### Performance
PairRM has been trained on various high-quality and large-scale dataset with human preference annotations and exhibits great correlation with human preferences 
with an extremly small model size (0.4B), approching the performance of GPT-4.

We test the pairwise comparison on 
- [Auto-J pairwise testdata](https://github.com/GAIR-NLP/auto-j#pairwise-response-comparison)
- [HHH-alignment](https://huggingface.co/datasets/HuggingFaceH4/hhh_alignment)
- [MT-bench-human-judgements](https://huggingface.co/datasets/lmsys/mt_bench_human_judgments)

#### Auto-J Pairwise test data performance

|         Model         |    Summ   |    Exam   |    Code   | Rewriting |   Crea W  |   Func W  |  Comm |    NLP   |  Overall  |
|:---------------------:|:---------:|:---------:|:---------:|:---------:|:---------:|:---------:|:-----:|:--------:|:---------:|
| Closed -source Models |
|        ChatGPT        |    33.3   |    40.3   |    36.6   |    31.6   |    48.2   |    40.4   |  47.6 |   45.8   |    42.7   |
|       Claude -2       |    30.6   |    36.1   |    41.7   |    34.2   |    48.1   |    42.5   |  40.6 |   48.5   |    42.4   |
|         GPT -4        |    59.7   |    51.4   |    69.2   |    58.3   |    66.7   |    60.4   |  58.3 |   65.2   |    61.9   |
|  Open -source Models  |
|        SteamSHP       |    33.3   |    29.2   |    26.7   |    33.3   |    40.7   |    31.3   |  51.4 |   51.9   |    40.6   |
|        PandaLM        |    29.2   |    33.3   |    31.7   |    23.3   |    43.5   |    32.9   |  44.8 |   48.9   |    38.9   |
|   LLaMA -2-Chat -13B  |    20.8   |    27.8   |    19.2   |     20    |    31.5   |    27.5   |  35.8 |   31.8   |     29    |
|    Vicuna -13B-v1.5   |    30.6   |    23.6   |     35    |    28.3   |    36.1   |    37.5   |  45.5 |   39.8   |    37.3   |
|   WizardLM -13B-v1.2  |    22.2   |    20.8   |    32.5   |    19.2   |    28.7   |    25.4   |  29.2 |    33    |    27.8   |
|   LLAMA -2-chat -70B  |    34.7   |    33.3   |    36.7   |    35.8   |    51.4   |    54.2   |  47.2 |   47.7   |    45.9   |
|       AUTO -J (13b)       |    45.8   |    38.9   |    59.2   |    47.5   |    54.6   |    57.1   |   **58**  |   57.6   |    54.8   |
|         **PairRM (0.4b)**       | **56.94** | **52.78** | **58.33** | **55.83** | **61.57** | **59.17** | 57.64 | **62.5** | **59.05** |

#### HHH-Alignment and MT-bench human judgements

|        Evaluator LM       | HHH ALIGNMENT |           |           |          |             | MT BENCH HUMAN JUDG . |
|:-------------------------:|:-------------:|:---------:|:---------:|:--------:|:-----------:|:---------------------:|
|                           |     Help .    |   Harm .  |   Hon .   |   Other  | Total Avg . |    Human Preference   |
|           RANDOM          |       50      |     50    |     50    |    50    |      50     |         34.26         |
|  STANFORDNLP REWARD MODEL |     69.49     |   60.34   |   52.46   |   51.16  |    58.82    |         44.79         |
|    ALMOST REWARD MODEL    |     74.58     |   67.24   |   78.69   |   86.05  |    76.02    |          49.9         |
|      LLAMA2 -CHAT 7B      |      66.1     |   81.03   |   70.49   |   74.42  |    72.85    |         51.78         |
|      LLAMA2 -CHAT 13B     |     74.58     |   87.93   |   55.74   |   79.07  |    73.76    |         52.34         |
|      LLAMA2 -CHAT 70B     |      66.1     |   **89.66**   |   67.21   |   74.42  |    74.21    |         53.67         |
| LLAMA2 -CHAT 13B+COARSE . |     68.74     |   68.97   |   65.57   |   67.44  |    67.42    |         46.89         |
|    GPT -3.5-TURBO -0613   |     76.27     |   87.93   |   67.21   |   86.05  |    78.73    |         57.12         |
|       PROMETHEUS 7B       |     69.49     |   84.48   |   78.69   |   90.7   |    80.09    |         55.14         |
|       PROMETHEUS 13B      |     81.36     |   82.76   |   75.41   |   76.74  |    79.19    |         57.72         |
|           **PairRM (0.4b)**          |   **84.75**   |   84.48   | **80.33** | **90.7** |  **84.62**  |         **59**        |
|        GPT -4-0613        |     91.53     |    93.1   |   85.25   |   83.72  |    88.69    |         63.87         |

**While PairRM is a extremely small model (0.4B) based on deberta, the pairwise comparison aggrement performance approches GPT-4's performance!**

Two reasons to attribute:
- Our PairRM specically designed model arch for pairwise comparison through bidirectional attention (See LLM-blender paper for more details)
- The high-quality and large-scale human preference annotation data it was train on (see training dataset list on this hugging face page)




## Citation
If you are using PairRM in your research, please cite LLM-blender.
```bibtex
@inproceedings{llm-blender-2023,
    title = "LLM-Blender: Ensembling Large Language Models with Pairwise Comparison and Generative Fusion",
    author = "Jiang, Dongfu and Ren, Xiang and Lin, Bill Yuchen",
    booktitle = "Proceedings of the 61th Annual Meeting of the Association for Computational Linguistics (ACL 2023)",
    year = "2023"
}

```