🎓 Large Language Models Know Your Contextual Search Intent: A Prompting Framework for Conversational Search [Work in Progress]

We present a prompting framework called LLMCS that leverages large language models to perform few-shot conversational query rewriting for conversational search.

We explore three prompting methods to generate multiple query rewrites and hypothetical responses, and propose to aggregate them into an integrated representation that can robustly represent the user’s real contextual search intent.

🌏 Environment

We conduct experiemnts in Python 3.8.13.

Main packages:

• Generating rewrites:

  • openai==0.26.4
  • numpy==1.23.5

• For evaluation:

  • torch==1.12.0+cu113
  • trec-car-tools==2.6
  • faiss-gpu
  • pyserini==0.17.0

conda create -n llmcs python=3.8
source activate llmcs
pip install -r requirements.txt

📑 Data

1. We provide the preprocessed cast19 and cast20 datasets in the datasets folder. Following existing work (e.g, ConvDR and COTED), we use the automatic canonical response as the last response for CAsT-20.

2. demonstrations.json contains four exemplars randomly sampled from the CAsT-22 dataset. We manually write CoT for all of its turns.

🏃 Running

LLMCS contains three prompting methods, including Rewriting Prompt (REW), Rewriting-Then-Response Prompt (RTR), and Rewriting-And-Response Prompt (RAR). We also design chain-of-thought tailored to conversational search intent understanding that can be incorporated into these prompting methods.

To get started, first, you should set your OpenAI API key in generator.py

# TODO: Write your OpenAI API here.
OPENAI_KEYS = [
    'Your key',
]

REW Prompting

To perform REW prompting, run:

bash scripts/run_prompt_rewrite.sh

Also, you can enable CoT by running:

bash scripts/run_prompt_cot_rewrite.sh

RTR Prompting

Similarly, to perform RTR prompting, run:

bash scripts/run_prompt_rewrite_then_response.sh

Note that you need to provide a pre-generated rewrite file into the field of rewrite_file_path for running prompt_rewrite_then_response.py. To enable CoT for RAR, you can set rewrite_file_path to the rewrite file generated using CoT.

--rewrite_file_path="./results/cast20/REW/rewrites.jsonl" \
# --rewrite_file_path="./results/cast20/COT-REW/rewrites.jsonl" \ +COT

RAR Prompting

Similarly, to perform RAR prompting, run:

bash scripts/run_prompt_rewrite_and_response.sh

Also, you can enable CoT by running:

bash scripts/run_prompt_cot_rewrite_and_response.sh

🥚 Results

A rewrites.jsonl file, which contains the rewrites or/and hypothetical responses, will be generated into the work_dir that you set in the running script.

We have provided our generated rewrites.jsonl files in the results folder.

The Keys of rewrites.jsonl:

• predicted_rewrite: rewrite (list)
• preidcted_response: hypothetical response (list)
• other auxiliary information

⚖️ Evaluation

We design three aggregation methods, including MaxProb, Mean, and SC, to get the final search intent vector. Then we perform dense retrieval with ANCE (click to download) for evaluation.

To perform evaluation, you should first build the dense index that contains all candidate passage embeddings. There have been many good public repositories that instruct how to build this index, such as AutoRewriter, ConvDR, and ConvTrans. One can refer them to build the index. All passage embeddings generated from ANCE are around 103GB.

Then, run the following script for evaluation:

cd evaluation
bash run_eval_dense_retrieval.sh

We have annotated the important arguments of run_eval_dense_retrieval.sh as below:

# eval_dense_retrieval.sh
# An example of evaluating RTR on cast20.
eval_field_name="predicted_rewrite"
work_dir="../results/cast20/RTR"    # set your the folder containing your `rewrites.jsonl`file

eval_file_path="$work_dir/rewrites.jsonl" \
index_path="" # set the pre-built index which contains all candidate passage emebddings. 
qrel_file_path="../datasets/cast20_qrel.tsv" # set the qrel file path
retrieval_output_path="$work_dir/ance/+q+r+sc" # set your expected output folder path

export CUDA_VISIBLE_DEVICES=0
python eval_dense_retrieval.py \
--eval_file_path=$eval_file_path \
--eval_field_name=$eval_field_name \
--qrel_file_path=$qrel_file_path \
--index_path=$index_path \
--retriever_path="" \ # set the pre-trained ANCE model path.
--use_gpu_in_faiss \
--n_gpu_for_faiss=1 \
--top_n=1000 \
--rel_threshold=2 \ # set 1 for cast19 and 2 for cast20.
--retrieval_output_path=$retrieval_output_path \
--include_query \
--include_response \ # enable `include_response` if you test RTR or RAR prompting.
--aggregation_method="sc" \ # you can set [`maxprob, mean, sc`]

Evaluation results that contains the following three files will be output into retrieval_output_path that you set.

• metrics.res: all evaluation metrics.
• parameters.txt: parameters record of the evaluation.
• res.trec: detailed TREC-style search results.

Main Results:

Retriever	System	CAsT-19	CAsT-20
		NDCG@3	NDCG@3
BM25	QuReTeC	0.338	0.171
BM25	T5QR	0.258	0.141
BM25	Manual	0.309	0.241
ANCE	QuReTeC	0.443	0.287
ANCE	T5QR	0.417	0.299
ANCE	Manual	0.461	0.422
ANCE	ConvDR	0.463	0.340
ANCE	COTED	0.478	0.342
ANCE	CRDR	0.472	0.350
ANCE	LLMCS (RAR + Mean)	0.506	0.465
	RI over Manual	9.8%	10.2%
	RI over 2nd-Best	5.9%	32.9%

Table 1: "RI over Manual or 2nd-Best" means "relative improvements over Manual or the second-best method except for Manual".

✍️ Reference

If you use LLMCS in a research paper, please cite our work as follows:

@article{mao2023llmcs,
  title={Large Language Models Know Your Contextual Search Intent: A Prompting Framework for Conversational Search},
  author={Mao, Kelong and Dou, Zhicheng and Chen, Haonan and Mo, Fengran and Qian, Hongjin},
  journal={arXiv preprint arXiv:2303.06573},
  year={2023}
}