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An Open-Source Package for Information Retrieval.

😃 What's New

  • Top Spot on TREC-COVID Challenge (May 2020, Round2)

    The twin goals of the challenge are to evaluate search algorithms and systems for helping scientists, clinicians, policy makers, and others manage the existing and rapidly growing corpus of scientific literature related to COVID-19, and to discover methods that will assist with managing scientific information in future global biomedical crises.
    >> Reproduce Our Submit >> About COVID-19 Dataset >> Our Paper


OpenMatch integrates excellent neural methods and technologies to provide a complete solution for deep text matching and understanding.

1/ Document Retrieval

Document Retrieval refers to extracting a set of related documents from large-scale document-level data based on user queries.

* Sparse Retrieval

Sparse Retriever is defined as a sparse bag-of-words retrieval model.

* Dense Retrieval

Dense Retriever performs retrieval by encoding documents and queries into dense low-dimensional vectors, and selecting the document that has the highest inner product with the query

2/ Document Reranking

Document reranking aims to further match user query and documents retrieved by the previous step with the purpose of obtaining a ranked list of relevant documents.

* Neural Ranker

Neural Ranker uses neural network as ranker to reorder documents.

* Feature Ensemble

Feature Ensemble can fuse neural features learned by neural ranker with the features of non-neural methods to obtain more robust performance

3/ Domain Transfer Learning

Domain Transfer Learning can leverages external knowledge graphs or weak supervision data to guide and help ranker to overcome data scarcity.

* Knowledge Enhancemnet

Knowledge Enhancement incorporates entity semantics of external knowledge graphs to enhance neural ranker.

* Data Augmentation

Data Augmentation leverages weak supervision data to improve the ranking accuracy in certain areas that lacks large scale relevance labels.

Stage Model Paper
1/ Sparse Retrieval BM25 Best Match25 ~Tool
1/ Dense Retrieval ANN Approximate nearest neighbor ~Tool
2/ Neural Ranker K-NRM End-to-End Neural Ad-hoc Ranking with Kernel Pooling ~Paper
2/ Neural Ranker Conv-KNRM Convolutional Neural Networks for Soft-Matching N-Grams in Ad-hoc Search ~Paper
2/ Neural Ranker TK Interpretable & Time-Budget-Constrained Contextualization for Re-Ranking ~Paper
2/ Neural Ranker BERT BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding ~Paper
2/ Feature Ensemble Coordinate Ascent Linear feature-based models for information retrieval. Information Retrieval ~Paper
3/ Knowledge Enhancement EDRM Entity-Duet Neural Ranking: Understanding the Role of Knowledge Graph Semantics in Neural Information Retrieval ~Paper
3/ Data Augmentation ReInfoSelect Selective Weak Supervision for Neural Information Retrieval ~Paper

Note that the BERT model is following huggingface's implementation - transformers, so other bert-like models are also available in our toolkit, e.g. electra, scibert.


* From PyPI

pip install git+

* From Source

git clone
cd OpenMatch
python install

* From Docker

To build an OpenMatch docker image from Dockerfile

docker build -t <image_name> .

To run your docker image just built above as a container

docker run --gpus all --name=<container_name> -it -v /:/all/ --rm <image_name>:<TAG>

Quick Start

* Detailed examples are available here.

import torch
import OpenMatch as om

query = "Classification treatment COVID-19"
doc = "By retrospectively tracking the dynamic changes of LYM% in death cases and cured cases, this study suggests that lymphocyte count is an effective and reliable indicator for disease classification and prognosis in COVID-19 patients."

* For bert-like models:

from transformers import AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("allenai/scibert_scivocab_uncased")
input_ids = tokenizer.encode(query, doc)
model = om.models.Bert("allenai/scibert_scivocab_uncased")
ranking_score, ranking_features = model(torch.tensor(input_ids).unsqueeze(0))

* For other models:

tokenizer ="./data/glove.6B.300d.txt")
query_ids, query_masks = tokenizer.process(query, max_len=16)
doc_ids, doc_masks = tokenizer.process(doc, max_len=128)
model = om.models.KNRM(vocab_size=tokenizer.get_vocab_size(),
ranking_score, ranking_features = model(torch.tensor(query_ids).unsqueeze(0),

* The GloVe can be downloaded using:

wget -P ./data
unzip ./data/ -d ./data

* Evaluation

metric = om.Metric()
res = metric.get_metric(qrels, ranking_list, 'ndcg_cut_20')
res = metric.get_mrr(qrels, ranking_list, 'mrr_cut_10')


* Ad-hoc Search

Retriever Reranker Coor-Ascent ClueWeb09 Robust04 ClueWeb12
SDM KNRM - 0.1880 0.3016 0.0968
SDM Conv-KNRM - 0.1894 0.2907 0.0896
SDM EDRM - 0.2015 0.2993 0.0937
SDM TK - 0.2306 0.2822 0.0966
SDM BERT Base - 0.2701 0.4168 0.1183
SDM ELECTRA Base - 0.2861 0.4668 0.1078

* MS MARCO Passage Ranking

Retriever Reranker Coor-Ascent dev eval
BM25 BERT Base - 0.349 0.345
BM25 ELECTRA Base - 0.352 0.344
BM25 RoBERTa Large - 0.386 0.375
BM25 ELECTRA Large - 0.388 0.376

* MS MARCO Document Ranking

Retriever Reranker Coor-Ascent dev eval
ANCE FirstP - - 0.373 0.334
ANCE MaxP - - 0.383 0.342
ANCE FirstP+BM25 BERT Base FirstP + 0.431 0.380
ANCE MaxP BERT Base MaxP + 0.432 0.391


Thanks to all the people who contributed to OpenMatch!

Kaitao Zhang, Si Sun, Zhenghao Liu, Aowei Lu

Project Organizers

  • Zhiyuan Liu
  • Chenyan Xiong
  • Maosong Sun


An Open-Source Package for Information Retrieval.





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